title: Fatherhood (film)

text: "Fatherhood" was initially scheduled to be released in theaters on April 3, 2020, but on January 6, 2020, it was delayed to January 8, 2021. Later that year, it was pushed back a week to January 15, 2021. On March 30, 2020, it was brought forward to October 23, 2020 due to the COVID-19 pandemic. On April 24, 2020, it was delayed to April 2, 2021, and on November 19, 2020, it was delayed again to April 16, 2021.


title: Fatherhood (film)

text: It was then announced that Netflix had acquired the worldwide distribution rights (except China) to the film from Sony Pictures Releasing, and set it for streaming release on June 18, 2021. The film was the most-watched item on the service in its first weekend. A week after its release, Netflix reported the film was on track to by watched by 61 million households through its first month of release.


title: Fatherhood (film)

text: "Fatherhood" was released on Blu-ray, DVD, and Digital HD on June 14, 2022 by Sony Pictures Home Entertainment.


title: Fatherhood (film)

text: On the review aggregator website Rotten Tomatoes, the film holds an approval rating of 66% based on 70 reviews, with an average rating of 6.7/10. The site's critics consensus reads, ""Fatherhood" offers few surprises, but strong work from a smartly assembled cast gives this fact-based story real emotional resonance." According to Metacritic, which assigned a weighted average score of 53 out of 100 based on 18 critics, the film received "mixed or average reviews."


title: Fatherhood (film)

text: William Bibbiani of the "TheWrap" praised Hart's "confidently laid-back and affable lead performance," and wrote, "Perhaps a little too slight to be memorable in the long run, this sensitive and charming tale reassures without, somehow, completely ignoring reality." From "The Hollywood Reporter", Lovia Gyarkye called the film "both an effective star vehicle and a tender tearjerker," and said, "Hart, usually known for his comedy... embraces a more dramatic side here, and is surprisingly convincing in these moments."


title: Charles Martinet

text: Charles Martinet (, ; born September 17, 1955) is an American actor and voice actor, known for his portrayal of both Mario and Luigi in the "Super Mario" video game series since 1992. He is also the voice of other characters in the series such as Wario, Waluigi, Baby Mario, and Baby Luigi.


title: Charles Martinet

text: Martinet is of French descent and speaks fluent French and Spanish. His family moved to Barcelona when he was 12 years old, and later to Paris. He attended the American School of Paris and graduated in 1974.


title: Charles Martinet

text: Martinet attended the University of California, Berkeley, where he originally intended to study international law. In his senior year he decided to discontinue his studies after a tutor told him to "regurgitate information he'd written in his book, chapter-by-chapter". A friend suggested to him to take acting classes to combat his fear of public speaking. His first role was a monologue from the "Spoon River Anthology". Eventually, Martinet earned an apprenticeship at the Berkeley Repertory Theatre. After training with the Berkeley Rep for several years, Martinet went to London to attend the Drama Studio London, where among other skills, he discovered his talent for accents and dialects. Upon returning to California he joined the Berkeley Repertory Theatre. He went on to become a founding member of the San Jose Repertory Theatre for four years.


title: Charles Martinet

text: Working for Nintendo since 1990, Martinet started voicing Mario at video game trade shows in which attendees would walk up to a TV screen displaying a 3-D Mario head that moved around the screen and talked. This system was called Mario in Real-Time or MIRT and was developed by Pasadena based SimGraphics. Martinet could see the attendees by means of a hidden camera setup, and a facial motion capture rig recorded his mouth movements in order to synchronize Martinet's mouth movement with the on-screen Mario mouth movement. This digital puppetry, with Martinet's comic performance, was a novelty at the time.


title: Charles Martinet

text: Martinet earned the job when, one day, he was told by his friend that there was going to be an audition at a trade show in which auditioneers "talk to people as a plumber". He went to the audition at the last minute as the casting directors were already putting away their equipment. Charles Martinet walked in and asked, "Can I please read for this?". The directors let him audition and told him, "You're an Italian plumber from Brooklyn". At first Martinet planned to talk like a stereotypical Italian American with a deep, raspy voice (which is how Mario sounded in the "Super Mario Bros. Super Show", "The Adventures of Super Mario Bros. 3" and "Super Mario World" cartoons). He then thought to himself that it would be too harsh for children to hear, so he made it more soft-hearted and friendly, resulting in what Mario's voice is today. Martinet has also stated that he kept on talking with his Mario voice until the audition tape ran out. He says that Petruchio from William Shakespeare's "The Taming of the Shrew" was an inspiration for his portrayal of Mario.


title: Charles Martinet

text: Martinet's official debut as Mario was in the 1992 "Super Mario Bros." pinball machine, despite being uncredited for the role. However, most were first exposed to Mario's voice in the landmark 1996 game "Super Mario 64". During the recording session, he and a few developers wondered what Mario would do when the player leaves him alone. In the end, Martinet came up with the idea that Mario would dream of pasta during his sleep, and in the final game, Mario says "night nighty. Ahhh spaghetti, ahhh ravioli, ahhh mamma mia" when in his second sleeping position. Following "Super Mario 64", he would go on to additionally voice Luigi, Wario, Waluigi, Metal Mario, Shadow Mario, Mini-Mario Toys, Baby Mario, Baby Luigi and Baby Wario in most games wherein these characters speak. He also voiced the enemies Wart, Mouser, Tryclyde, and Clawgrip in "Super Mario Advance". His voice work appears in the English and Japanese language versions of the games. With his work as Mario in "Super Smash Bros. Ultimate", the Guinness Book of World Records recognized Martinet for having performed the same character in one hundred different titles, the most of any video game voice actor.


title: Charles Martinet

text: Martinet provided voiceover acting for the boxers and the announcer in the Super NES title "Super Punch-Out!!". He voiced the character Vigoro in Sega's Dreamcast and Nintendo GameCube role-playing video game, "Skies of Arcadia". He did the voice of Homunculus in the Konami PlayStation 2, Xbox and Windows game "Shadow of Destiny", and provided voices for "Reader Rabbit" and "The ClueFinders" games. In 2009, Martinet told "That Gaming Site" that he wanted to voice Link in "", but Shigeru Miyamoto told him that Link would remain without a voice. However, Link's grunts have been voiced by various Japanese voice actors.


title: Charles Martinet

text: In addition to video game voiceovers, Martinet has worked as a voice actor in commercials, cartoons, and promotions. At the Electronic Entertainment Expo (E3) trade show in 2005, Martinet remotely interacted with players from his New York apartment in a playable demo of "". Martinet did Mario's voice as the announcer for "Pac-Man Vs." on the Nintendo GameCube.


title: Charles Martinet

text: Other than the "Mario" series, Martinet has also done work for the video game "Cel Damage" as the voice of Fowl Mouth, as well as the primary voice work in several educational game series such as LeapFrog. He also voiced the dragon Paarthurnax in the 2011 video game "", Orvus in 2009's "", and narrated the cutscenes and menus for the 2013 video game "Runner2" and "Runner3", appearing as a hidden playable character in the latter. Martinet also narrated for the 2020 Netflix docuseries "High Score". Martinet provided the voice of Magenta in the English dub of the 2022 anime film "".


title: Charles Martinet

text: As the voice of Mario, Martinet has become a well-known personality and has made public appearances at several video game related events where he meets fans for chat, photographs, and autographs. He has made regular appearances at game events such as Electronic Entertainment Expo, Gamescom, and the Eurogamer Expo, and at launch events of games like "Super Mario Galaxy" and its sequel.


title: Eugene V. Debs

text: Eugene Victor "Gene" Debs (November 5, 1855 – October 20, 1926) was an American socialist, political activist, trade unionist, one of the founding members of the Industrial Workers of the World (IWW), and five times the candidate of the Socialist Party of America for President of the United States. Through his presidential candidacies as well as his work with labor movements, Debs eventually became one of the best-known socialists living in the United States.


title: Eugene V. Debs

text: Early in his political career, Debs was a member of the Democratic Party. He was elected as a Democrat to the Indiana General Assembly in 1884. After working with several smaller unions, including the Brotherhood of Locomotive Firemen, Debs led his union in a major ten-month strike against the CB&Q Railroad in 1888. Debs was instrumental in the founding of the American Railway Union (ARU), one of the nation's first industrial unions. After workers at the Pullman Palace Car Company organized a wildcat strike over pay cuts in the summer of 1894, Debs signed many into the ARU. He led a boycott by the ARU against handling trains with Pullman cars in what became the nationwide Pullman Strike, affecting most lines west of Detroit and more than 250,000 workers in 27 states. Purportedly to keep the mail running, President Grover Cleveland used the United States Army to break the strike. As a leader of the ARU, Debs was convicted of federal charges for defying a court injunction against the strike and served six months in prison.


title: Eugene V. Debs

text: In prison, Debs read various works of socialist theory and emerged six months later as a committed adherent of the international socialist movement. Debs was a founding member of the Social Democracy of America (1897), the Social Democratic Party of America (1898) and the Socialist Party of America (1901). Debs ran as a Socialist candidate for President of the United States five times, including 1900 (earning 0.6 percent of the popular vote), 1904 (3.0 percent), 1908 (2.8 percent), 1912 (6.0 percent), and 1920 (3.4 percent), the last time from a prison cell. He was also a candidate for United States Congress from his native state Indiana in 1916.


title: Eugene V. Debs

text: Debs was noted for his oratorical skills, and his speech denouncing American participation in World War I led to his second arrest in 1918. He was convicted under the Sedition Act of 1918 and sentenced to a ten-year term. President Warren G. Harding commuted his sentence in December 1921. Debs died in 1926, not long after being admitted to a sanatorium due to cardiovascular problems that developed during his time in prison.


title: Eugene V. Debs

text: Eugene Victor "Gene" Debs was born on November 5, 1855, in Terre Haute, Indiana, to Jean Daniel and Marguerite Mari Bettrich Debs, who immigrated to the United States from Colmar, Alsace, France. His father, who came from a prosperous family, owned a textile mill and meat market. Debs was named after the French authors Eugène Sue and Victor Hugo.


title: Eugene V. Debs

text: Debs attended public school, dropping out of high school at age 14. He took a job with the Vandalia Railroad cleaning grease from the trucks of freight engines for fifty cents a day. He later became a painter and car cleaner in the railroad shops. In December 1871, when a drunken locomotive fireman failed to report for work, Debs was pressed into service as a night fireman. He decided to remain a fireman on the run between Terre Haute and Indianapolis, earning more than a dollar a night for the next three and half years.


title: Eugene V. Debs

text: In July 1875, Debs left to work at a wholesale grocery house, where he remained for four years while attending a local business school at night.


title: Eugene V. Debs

text: Debs joined the Brotherhood of Locomotive Firemen (BLF) in February 1875 and became active in the organization. In 1877 he served as a delegate of the Terre Haute lodge to the organization's national convention. Debs was elected associate editor of the BLF's monthly organ, "Firemen's Magazine", in 1878. Two years later, he was appointed Grand Secretary and Treasurer of the BLF and editor of the magazine in July 1880. He worked as a BLF functionary until January 1893 and as the magazine's editor until September 1894.


title: Eugene V. Debs

text: At the same time, he became a prominent figure in the community. He served two terms as Terre Haute's city clerk from September 1879 to September 1883. In the fall of 1884, he was elected as a Democrat to represent Terre Haute and Vigo County in the Indiana General Assembly. He served for one term in 1885.


title: Eugene V. Debs

text: Debs married Katherine "Kate" Metzel on June 9, 1885 at an Episcopal church. Their home still stands in Terre Haute, preserved on the campus of Indiana State University.


title: Eugene V. Debs

text: The railroad brotherhoods were comparatively conservative organizations, focused on providing fellowship and services rather than on collective bargaining. Their motto was "Benevolence, Sobriety, and Industry". As editor of the official journal of the Brotherhood of Locomotive Firemen, Debs initially concentrated on improving the brotherhood's death and disability insurance programs. During the early 1880s, Debs's writing stressed themes of self-upliftment: temperance, hard work, and honesty. Debs also held the view that "labor and capital are friends" and opposed strikes as a means of settling differences. The brotherhood had never authorized a strike from its founding in 1873 to 1887, a record which Debs was proud of. Railroad companies cultivated the brotherhood and granted them perks like free transportation to their conventions for the delegates. Debs also invited railroad president Henry C. Lord to write for the magazine. Summarizing Debs's thought in this period, the historian David A. Shannon wrote: "Debs's desideratum was one of peace and co-operation between labor and capital, but he expected management to treat labor with respect, honor and social equality".


title: Eugene V. Debs

text: Debs gradually became convinced of the need for a more unified and confrontational approach as railroads were powerful forces in the economy. One influence was his involvement in the Burlington Railroad Strike of 1888, a defeat for labor that convinced Debs of "the need to reorganize across craft lines", according to Joanne Reitano. After stepping down as Brotherhood Grand Secretary in 1893, Debs organized one of the first industrial unions in the United States, the American Railway Union (ARU), for unskilled workers. He was elected president of the ARU upon its founding, with fellow railway labor organizer George W. Howard as first vice president. The union successfully struck the Great Northern Railway in April 1894, winning most of its demands.


title: Eugene V. Debs

text: In 1894, Debs became involved in the Pullman Strike, which grew out of a compensation dispute started by the workers who constructed the rail cars made by the Pullman Palace Car Company. The Pullman Company, citing falling revenue after the economic Panic of 1893, had cut the wages of its employees by twenty-eight percent. The workers, many of whom were already members of the ARU, appealed for support to the union at its convention in Chicago, Illinois. Debs tried to persuade union members, who worked on the railways, that the boycott was too risky given the hostility of the railways and the federal government, the weakness of the union, and the possibility that other unions would break the strike.


title: Eugene V. Debs

text: The membership ignored his warnings and refused to handle Pullman cars or any other railroad cars attached to them, including cars containing US Mail. After ARU Board Director Martin J. Elliott extended the strike to St. Louis, doubling its size to eighty thousand workers, Debs relented and decided to take part in the strike, which was now endorsed by almost all members of the ARU in the immediate area of Chicago. On July 9, 1894, a "New York Times" editorial called Debs "a lawbreaker at large, an enemy of the human race". Strikers fought by establishing boycotts of Pullman train cars and with Debs's eventual leadership the strike came to be known as "Debs' Rebellion".


title: Eugene V. Debs

text: The federal government intervened, obtaining an injunction against the strike on the grounds that the strikers had obstructed the US Mail, carried on Pullman cars, by refusing to show up for work. President Grover Cleveland, whom Debs had supported in all three of his presidential campaigns, sent the United States Army to enforce the injunction. The presence of the army was enough to break the strike. Overall, thirty strikers were killed in the strike, thirteen of them in Chicago, and thousands were blacklisted. An estimated $80 million worth of property was damaged and Debs was found guilty of contempt of court for violating the injunction and sent to federal prison.


title: Eugene V. Debs

text: Debs was represented by Clarence Darrow, later a leading American lawyer and civil libertarian, who had previously been a corporate lawyer for the railroad company. While it is commonly thought that Darrow "switched sides" to represent Debs, a myth repeated by Irving Stone's biography, "Clarence Darrow For the Defense", he had in fact resigned from the railroad earlier, after the death of his mentor William Goudy. A Supreme Court case decision, "In re Debs", later upheld the right of the federal government to issue the injunction.


title: Eugene V. Debs

text: At the time of his arrest for mail obstruction, Debs was not yet a socialist. While serving his six-month term in the jail at Woodstock, Illinois, Debs and his ARU comrades received a steady stream of letters, books and pamphlets in the mail from socialists around the country. Debs recalled several years later:


title: Eugene V. Debs

text: I began to read and think and dissect the anatomy of the system in which workingmen, however organized, could be shattered and battered and splintered at a single stroke. The writings of [Edward] Bellamy and [Robert] Blatchford early appealed to me. "The Cooperative Commonwealth" of [Laurence] Gronlund also impressed me, but the writings of [Karl] Kautsky were so clear and conclusive that I readily grasped, not merely his argument, but also caught the spirit of his socialist utterance – and I thank him and all who helped me out of darkness into light.


title: Eugene V. Debs

text: Additionally, Debs was visited in jail by the Milwaukee socialist newspaper editor Victor L. Berger, who in Debs's words "came to Woodstock, as if a providential instrument, and delivered the first impassioned message of Socialism I had ever heard". In his 1926 obituary in "Time", it was said that Berger left him a copy of "Das Kapital" and "prisoner Debs read it slowly, eagerly, ravenously". Debs emerged from jail at the end of his sentence a changed man. He would spend the final three decades of his life proselytizing for the socialist cause.


title: Eugene V. Debs

text: After Debs and Martin Elliott were released from prison in 1895, Debs started his socialist political career. Debs started agitating for the ARU membership to form a Social Democratic organization. In 1896, Debs supported Democratic candidate William Jennings Bryan in the presidential election following Bryan's Cross of Gold speech. After Bryan's loss in the election, a disappointed Debs decided for certain that the future for socialist policies lay outside the Democratic Party. In June 1897, the ARU membership finally joined with the Brotherhood of the Cooperative Commonwealth to form the Social Democracy of America.


title: Eugene V. Debs

text: Debs's wife Kate was opposed to socialism and was "hostile" to Debs's socialist activism as "it threatened her sense of middle-class respectability". The "tempestuous relationship with a wife who rejects the very values he holds most dear" was the basis of Irving Stone's biographical novel "Adversary in the House".


title: Eugene V. Debs

text: The Social Democracy of America (SDA), founded in June 1897 by Eugene V. Debs from the remnants of his American Railway Union, was deeply divided between those who favored a tactic of launching a series of colonies to build socialism by practical example and others who favored establishment of a European-style socialist political party with a view to capture of the government apparatus through the ballot box.


title: Eugene V. Debs

text: The June 1898 convention would be the group's last, with the minority political action wing quitting the organization to establish a new organization, the Social Democratic Party of America (SDP), also called the Social Democratic Party of the United States. Debs was elected to the National Executive Board, the five-member committee which governed the party, and his brother, Theodore Debs, was selected as its paid executive secretary, handling day-to-day affairs of the organization. Although by no means the sole decision-maker in the organization, Debs's status as prominent public figure in the aftermath of the Pullman strike provided cachet and made him the recognized spokesman for the party in the newspapers.


title: Eugene V. Debs

text: Along with Elliott, who ran for Congress in 1900, Debs was the first federal office candidate for the fledgling socialist party, running unsuccessfully for president the same year. Debs and his running mate Job Harriman received 87,945 votes (0.6 percent of the popular vote) and no electoral votes.


title: Eugene V. Debs

text: Following the 1900 Election, the Social Democratic Party and dissidents who had split from the Socialist Labor Party in 1899 unified forces at a Socialist Unity Convention held in Indianapolis in mid-1901 – a meeting which established the Socialist Party of America (SPA).


title: Eugene V. Debs

text: Debs was the Socialist Party of America candidate for president in 1904, 1908, 1912, and 1920 (the final time from prison). Though he received increasing numbers of popular votes in each subsequent election, he never won any votes in the Electoral College. In both 1904 and 1908, Debs ran with running-mate Ben Hanford. They received 402,810 votes in 1904, for 3.0 percent of the popular vote and an overall third-place finish. In the 1908 election, they received a slightly higher number of votes (420,852) than in their previous run, but at 2.8 percent, a smaller percentage of the total votes cast. In 1912, Debs ran with Emil Seidel as a running mate and received 901,551 votes, which was 6.0 percent of the popular vote, which remains the all-time highest percentage of the vote for a Socialist Party candidate in a US presidential election. Though Debs won no state's electoral votes, in Florida, he came in second behind Wilson and ahead of President William Howard Taft and former President Teddy Roosevelt. Finally, in 1920, running with Seymour Stedman, Debs won 913,693 votes, which remains the all-time high number of votes for a Socialist Party candidate in a US presidential election. Notably, the Nineteenth Amendment passed in 1920, granting women the federal right to vote across the country, and with the expanded voting pool, his vote total accounted for only 3.4 percent of the total number of votes cast. The size of the vote is nevertheless remarkable since Debs was at the time a federal prisoner in jail for sedition, though he promised to pardon himself if elected.


title: Eugene V. Debs

text: Although he received some success as a third-party candidate, Debs was largely dismissive of the electoral process as he distrusted the political bargains that Victor Berger and other "sewer socialists" had made in winning local offices. He put much more value on organizing workers into unions, favoring unions that brought together all workers in a given industry over those organized by the craft skills workers practiced.


title: Eugene V. Debs

text: After his work with the Brotherhood of Locomotive Firemen and the American Railway Union, Debs's next major work in organizing a labor union came during the founding of the Industrial Workers of the World (IWW). On June 27, 1905, in Chicago, Illinois, Debs and other influential union leaders including Bill Haywood, leader of the Western Federation of Miners; and Daniel De Leon, leader of the Socialist Labor Party, held what Haywood called the "Continental Congress of the working class". Haywood stated: "We are here to confederate the workers of this country into a working-class movement that shall have for its purpose the emancipation of the working class". Debs stated: "We are here to perform a task so great that it appeals to our best thought, our united energies, and will enlist our most loyal support; a task in the presence of which weak men might falter and despair, but from which it is impossible to shrink without betraying the working class".


title: Eugene V. Debs

text: Although the IWW was built on the basis of uniting workers of industry, a rift began between the union and the Socialist Party. It started when the electoral wing of the Socialist Party, led by Victor Berger and Morris Hillquit, became irritated with speeches by Haywood. In December 1911, Haywood told a Lower East Side audience at New York's Cooper Union that parliamentary Socialists were "step-at-a-time people whose every step is just a little shorter than the preceding step". It was better, Haywood said, to "elect the superintendent of some branch of industry, than to elect some congressman to the United States Congress". In response, Hillquit attacked the IWW as "purely anarchistic".


title: Eugene V. Debs

text: The Cooper Union speech was the beginning of a split between Haywood and the Socialist Party, leading to the split between the factions of the IWW, one faction loyal to the Socialist Party and the other to Haywood. The rift presented a problem for Debs, who was influential in both the IWW and the Socialist Party. The final straw between Haywood and the Socialist Party came during the Lawrence Textile Strike, when disgusted with the decision of the elected officials in Lawrence, Massachusetts, to send police, who subsequently used their clubs on children, Haywood publicly declared that "I will not vote again" until such a circumstance was rectified. Haywood was purged from the National Executive Committee by passage of an amendment that focused on the direct action and sabotage tactics advocated by the IWW. Debs was probably the only person who could have saved Haywood's seat.


title: Eugene V. Debs

text: In 1906, when Haywood had been on trial for his life in Idaho, Debs had described him as "the Lincoln of Labor" and called for Haywood to run against Theodore Roosevelt for president, but times had changed and Debs, facing a split in the party, chose to echo Hillquit's words, accusing the IWW of representing anarchy. Debs thereafter stated that he had opposed the amendment, but that once it was adopted it should be obeyed. Debs remained friendly to Haywood and the IWW after the expulsion despite their perceived differences over IWW tactics.


title: Eugene V. Debs

text: Prior to Haywood's dismissal, the Socialist Party membership had reached an all-time high of 135,000. One year later, four months after Haywood was recalled, the membership dropped to 80,000. The reformists in the Socialist Party attributed the decline to the departure of the "Haywood element" and predicted that the party would recover, but it did not. In the election of 1912, many of the Socialists who had been elected to public office lost their seats.


title: Eugene V. Debs

text: Debs was noted by many to be a charismatic speaker who sometimes called on the vocabulary of Christianity and much of the oratorical style of evangelism, even though he was generally disdainful of organized religion. Howard Zinn opined that "Debs was what every socialist or anarchist or radical should be: fierce in his convictions, kind and compassionate in his personal relations." Heywood Broun noted in his eulogy for Debs, quoting a fellow Socialist: "That old man with the burning eyes actually believes that there can be such a thing as the brotherhood of man. And that's not the funniest part of it. As long as he's around I believe it myself".


title: Eugene V. Debs

text: Although sometimes called "King Debs", Debs himself was not wholly comfortable with his standing as a leader. As he told an audience in Detroit in 1906:


title: Eugene V. Debs

text: Debs's speeches against the Wilson administration and the war earned the enmity of President Woodrow Wilson, who later called Debs a "traitor to his country". On June 16, 1918, Debs made a speech in Canton, Ohio, urging resistance to the military draft. He was arrested on June 30 and charged with ten counts of sedition.


title: Eugene V. Debs

text: His trial defense called no witnesses, asking that Debs be allowed to address the court in his defense. That unusual request was granted, and Debs spoke for two hours. He was found guilty on September 12. At his sentencing hearing on September 14, he again addressed the court and his speech has become a classic. Heywood Broun, a liberal journalist and not a Debs partisan, said it was "one of the most beautiful and moving passages in the English language. He was for that one afternoon touched with inspiration. If anyone told me that tongues of fire danced upon his shoulders as he spoke, I would believe it." Debs said in part:


title: Eugene V. Debs

text: Your honor, I have stated in this court that I am opposed to the form of our present government; that I am opposed to the social system in which we live; that I believe in the change of both but by perfectly peaceable and orderly means. ...


title: Eugene V. Debs

text: I am thinking this morning of the men in the mills and factories; I am thinking of the women who, for a paltry wage, are compelled to work out their lives; of the little children who, in this system, are robbed of their childhood, and in their early, tender years, are seized in the remorseless grasp of Mammon, and forced into the industrial dungeons, there to feed the machines while they themselves are being starved body and soul. ...


title: Eugene V. Debs

text: Your honor, I ask no mercy, I plead for no immunity. I realize that finally the right must prevail. I never more fully comprehended than now the great struggle between the powers of greed on the one hand and upon the other the rising hosts of freedom. I can see the dawn of a better day of humanity. The people are awakening. In due course of time they will come into their own.


title: Eugene V. Debs

text: When the mariner, sailing over tropic seas, looks for relief from his weary watch, he turns his eyes toward the Southern Cross, burning luridly above the tempest-vexed ocean. As the midnight approaches the Southern Cross begins to bend, and the whirling worlds change their places, and with starry finger-points the Almighty marks the passage of Time upon the dial of the universe; and though no bell may beat the glad tidings, the look-out knows that the midnight is passingthat relief and rest are close at hand.


title: Eugene V. Debs

text: Let the people take heart and hope everywhere, for the cross is bending, midnight is passing, and joy cometh with the morning.


title: Eugene V. Debs

text: Debs was sentenced on September 18, 1918, to ten years in prison and was also disenfranchised for life. Debs presented what has been called his best-remembered statement at his sentencing hearing:


title: Eugene V. Debs

text: Your Honor, years ago I recognized my kinship with all living beings, and I made up my mind that I was not one bit better than the meanest on earth. I said then, and I say now, that while there is a lower class, I am in it, and while there is a criminal element, I am of it, and while there is a soul in prison, I am not free.


title: Eugene V. Debs

text: Debs appealed his conviction to the Supreme Court. In its ruling on "Debs v. United States", the court examined several statements Debs had made regarding World War I and socialism. While Debs had carefully worded his speeches in an attempt to comply with the Espionage Act, the Court found he had the intention and effect of obstructing the draft and military recruitment. Among other things, the Court cited Debs's praise for those imprisoned for obstructing the draft. Justice Oliver Wendell Holmes Jr. stated in his opinion that little attention was needed since Debs's case was essentially the same as that of "Schenck v. United States", in which the court had upheld a similar conviction.


title: Eugene V. Debs

text: Debs went to prison on April 13, 1919. In protest of his jailing, Charles Ruthenberg led a parade of unionists, socialists, anarchists, and communists on May 1 (May Day) in Cleveland, Ohio. The event quickly broke into the violent May Day riots of 1919.


title: Eugene V. Debs

text: Debs ran for president in the 1920 election while imprisoned in the Atlanta Federal Penitentiary. He received 919,799 votes (3.4 percent), slightly less than he had won in 1912, when he received 6 percent, the highest number of votes for a Socialist Party presidential candidate in the United States. During his time in prison, Debs wrote a series of columns deeply critical of the prison system. They appeared in sanitized form in the Bell Syndicate and were published in his only book, "Walls and Bars", with several added chapters. It was published posthumously.


title: Eugene V. Debs

text: In March 1919, President Wilson asked Attorney General A. Mitchell Palmer for his opinion on clemency, offering his own: "I doubt the wisdom and public effect of such an action." Palmer generally favored releasing people convicted under the wartime security acts, but when he consulted with Debs's prosecutorseven those with records as defenders of civil libertiesthey assured him that Debs's conviction was correct and his sentence appropriate. The President and his Attorney General both believed that public opinion opposed clemency and that releasing Debs could strengthen Wilson's opponents in the debate over the ratification of the peace treaty. Palmer proposed clemency in August and October 1920 without success. At one point, Wilson wrote: "While the flower of American youth was pouring out its blood to vindicate the cause of civilization, this man, Debs, stood behind the lines sniping, attacking, and denouncing them. ... This man was a traitor to his country and he will never be pardoned during my administration." In January 1921, Palmer, citing Debs's deteriorating health, proposed to Wilson that Debs receive a presidential pardon freeing him on February 12, Lincoln's birthday. Wilson returned the paperwork after writing "Denied" across it.


title: Eugene V. Debs

text: On December 23, 1921, President Warren G. Harding commuted Debs's sentence to time served, effective Christmas Day. He did not issue a pardon. A White House statement summarized the administration's view of Debs's case:


title: Eugene V. Debs

text: There is no question of his guilt. ... He was by no means, however, as rabid and outspoken in his expressions as many others, and but for his prominence and the resulting far-reaching effect of his words, very probably might not have received the sentence he did. He is an old man, not strong physically. He is a man of much personal charm and impressive personality, which qualifications make him a dangerous man calculated to mislead the unthinking and affording excuse for those with criminal intent.


title: Eugene V. Debs

text: When Debs was released from the Atlanta Penitentiary, the other prisoners sent him off with "a roar of cheers" and a crowd of fifty thousand greeted his return to Terre Haute to the accompaniment of band music. En route home, Debs was warmly received at the White House by Harding, who greeted him by saying: "Well, I've heard so damned much about you, Mr. Debs, that I am now glad to meet you personally."


title: Eugene V. Debs

text: In 1924, Debs was nominated for the Nobel Peace Prize by the Finnish Socialist Karl H. Wiik on the grounds that "Debs started to work actively for peace during World War I, mainly because he considered the war to be in the interest of capitalism."


title: Eugene V. Debs

text: He spent his remaining years trying to recover his health, which was severely undermined by prison confinement. In late 1926, he was admitted to Lindlahr Sanitarium in Elmhurst, Illinois. He died there of heart failure on October 20, 1926, at the age of 70. His body was cremated and buried in Highland Lawn Cemetery in Terre Haute, Indiana.


title: Eugene V. Debs

text: Debs helped motivate the American left to organize political opposition to corporations and World War I. American socialists, communists, and anarchists honor his work for the labor movement and motivation to have the average working man build socialism without large state involvement. Several books have been written about his life as an inspirational American socialist.


title: Eugene V. Debs

text: The Vermont senator and presidential candidate Bernie Sanders has long been an admirer of Debs and produced in 1979 a documentary about Debs which was released as a film and an audio LP record as an audio-visual teaching aid. In the documentary, he described Debs as "probably the most effective and popular leader that the American working class has ever had". Sanders hung a portrait of Debs in city hall in Burlington, Vermont, when he served as mayor of the city in the 1980s and has a plaque dedicated to Debs in his congressional office.


title: Eugene V. Debs

text: On May 22, 1962, Debs's home was purchased for $9,500 by the Eugene V. Debs Foundation, which worked to preserve it as a Debs memorial. In 1965 it was designated as an official historic site of the state of Indiana, and in 1966 it was designated as a National Historic Landmark of the United States. The preservation of the museum is monitored by the National Park Service. In 1990, the Department of Labor named Debs a member of its Labor Hall of Fame.


title: Eugene V. Debs

text: While Debs did not leave a collection of papers to a university library, the pamphlet collection which he and his brother amassed is held by Indiana State University in Terre Haute. The scholar Bernard Brommel, author of a 1978 biography of Debs, has donated his biographical research materials to the Newberry Library in Chicago, where they are open to researchers. The original manuscript of Debs's book "Walls and Bars", with handwritten amendments, presumably by Debs, is held in the Thomas J. Morgan Papers in the special collections department of the University of Chicago Library.


title: Eugene V. Debs

text: Eugene Township in Lake of the Woods County, Minnesota, was likely named after Debs. The community of Debs in Minnesota's Beltrami County may have also been named after him.


title: Eugene V. Debs

text: Eugene V Debs Hall in Buffalo, NY is a 501(c)7 nonprofit social club; and home to the Eugene V. Debs Local Initiative, a project to document and commemorate Buffalo's labor movement history.


title: Eugene V. Debs

text: Debs Place, a housing block in Co-op City in the Bronx, New York, was named in his honor. The Eugene V. Debs Cooperative House in Ann Arbor, Michigan, was named after Debs.


title: Kwon Nara

text: Kwon Na-ra () (changed her name legally to Kwon Ah-yoon (), known by her birth name Nara), is a South Korean singer and actress. She is best known as one of the original members of the South Korean girl group Hello Venus.


title: Kwon Nara

text: Nara became an acting trainee for Fantagio Entertainment when she was in middle school. She joined the girl group Hello Venus as a founding member where she went by the stage name "Nara". They debuted on May 9, 2012, with the mini-album "Venus", which contained four tracks. The single "Venus" reached number 35 on the Gaon chart.


title: Kwon Nara

text: Aside from her group activities, Nara appeared as a cameo role as a stewardess on the 20th episode of the SBS drama "Take Care of Us, Captain" with fellow Hello Venus member, Yooyoung.


title: Kwon Nara

text: In 2017, Nara played her first major acting role in SBS's romantic comedy drama "Suspicious Partner".


title: Kwon Nara

text: In 2020, she starred in JTBC drama "Itaewon Class", based on the webtoon of the same name. The series was a commercial success and became the seventh highest-rated Korean dramas in cable television history. She was also cast in historical comedy TV series "Royal Secret Agent" as Hong Da-In, a courtesan whose beauty is comparable to Hwang Jini.


title: Kwon Nara

text: In March 2021, Nara was confirmed to be starring in tvN's fantasy drama "". in the role of Min Sang-woon, a woman who used to be an immortal, but goes through a tragic event that turns her into a human. The drama premiered in December 2021.


title: Kwon Nara

text: In September 2022, Nara joined an essemble casts featuring actors from television dramas "Love in the Moonlight", "Itaewon Class", and "The Sound of Magic" in the "TVING"-produced reality tv show "Young Actors' Retreat".


title: Action potential

text: An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, called excitable cells, which include neurons, muscle cells, and in some plant cells. Certain endocrine cells such as pancreatic beta cells, and certain cells of the anterior pituitary gland are also excitable cells.


title: Action potential

text: In neurons, action potentials play a central role in cell–cell communication by providing for—or with regard to saltatory conduction, assisting—the propagation of signals along the neuron's axon toward synaptic boutons situated at the ends of an axon; these signals can then connect with other neurons at synapses, or to motor cells or glands. In other types of cells, their main function is to activate intracellular processes. In muscle cells, for example, an action potential is the first step in the chain of events leading to contraction. In beta cells of the pancreas, they provoke release of insulin. Action potentials in neurons are also known as "nerve impulses" or "spikes", and the temporal sequence of action potentials generated by a neuron is called its "spike train". A neuron that emits an action potential, or nerve impulse, is often said to "fire".


title: Action potential

text: Action potentials are generated by special types of voltage-gated ion channels embedded in a cell's plasma membrane. These channels are shut when the membrane potential is near the (negative) resting potential of the cell, but they rapidly begin to open if the membrane potential increases to a precisely defined threshold voltage, depolarising the transmembrane potential. When the channels open, they allow an inward flow of sodium ions, which changes the electrochemical gradient, which in turn produces a further rise in the membrane potential towards zero. This then causes more channels to open, producing a greater electric current across the cell membrane and so on. The process proceeds explosively until all of the available ion channels are open, resulting in a large upswing in the membrane potential. The rapid influx of sodium ions causes the polarity of the plasma membrane to reverse, and the ion channels then rapidly inactivate. As the sodium channels close, sodium ions can no longer enter the neuron, and they are then actively transported back out of the plasma membrane. Potassium channels are then activated, and there is an outward current of potassium ions, returning the electrochemical gradient to the resting state. After an action potential has occurred, there is a transient negative shift, called the afterhyperpolarization.


title: Action potential

text: In animal cells, there are two primary types of action potentials. One type is generated by voltage-gated sodium channels, the other by voltage-gated calcium channels. Sodium-based action potentials usually last for under one millisecond, but calcium-based action potentials may last for 100 milliseconds or longer. In some types of neurons, slow calcium spikes provide the driving force for a long burst of rapidly emitted sodium spikes. In cardiac muscle cells, on the other hand, an initial fast sodium spike provides a "primer" to provoke the rapid onset of a calcium spike, which then produces muscle contraction.


title: Action potential

text: Nearly all cell membranes in animals, plants and fungi maintain a voltage difference between the exterior and interior of the cell, called the membrane potential. A typical voltage across an animal cell membrane is −70 mV. This means that the interior of the cell has a negative voltage relative to the exterior. In most types of cells, the membrane potential usually stays fairly constant. Some types of cells, however, are electrically active in the sense that their voltages fluctuate over time. In some types of electrically active cells, including neurons and muscle cells, the voltage fluctuations frequently take the form of a rapid upward (positive) spike followed by a rapid fall. These up-and-down cycles are known as "action potentials". In some types of neurons, the entire up-and-down cycle takes place in a few thousandths of a second. In muscle cells, a typical action potential lasts about a fifth of a second. In plant cells, an action potential may last three seconds or more.


title: Action potential

text: The electrical properties of a cell are determined by the structure of its membrane. A cell membrane consists of a lipid bilayer of molecules in which larger protein molecules are embedded. The lipid bilayer is highly resistant to movement of electrically charged ions, so it functions as an insulator. The large membrane-embedded proteins, in contrast, provide channels through which ions can pass across the membrane. Action potentials are driven by channel proteins whose configuration switches between closed and open states as a function of the voltage difference between the interior and exterior of the cell. These voltage-sensitive proteins are known as voltage-gated ion channels.


title: Action potential

text: All cells in animal body tissues are electrically polarized – in other words, they maintain a voltage difference across the cell's plasma membrane, known as the membrane potential. This electrical polarization results from a complex interplay between protein structures embedded in the membrane called ion pumps and ion channels. In neurons, the types of ion channels in the membrane usually vary across different parts of the cell, giving the dendrites, axon, and cell body different electrical properties. As a result, some parts of the membrane of a neuron may be excitable (capable of generating action potentials), whereas others are not. Recent studies have shown that the most excitable part of a neuron is the part after the axon hillock (the point where the axon leaves the cell body), which is called the axonal initial segment, but the axon and cell body are also excitable in most cases.


title: Action potential

text: Each excitable patch of membrane has two important levels of membrane potential: the resting potential, which is the value the membrane potential maintains as long as nothing perturbs the cell, and a higher value called the threshold potential. At the axon hillock of a typical neuron, the resting potential is around –70 millivolts (mV) and the threshold potential is around –55 mV. Synaptic inputs to a neuron cause the membrane to depolarize or hyperpolarize; that is, they cause the membrane potential to rise or fall. Action potentials are triggered when enough depolarization accumulates to bring the membrane potential up to threshold. When an action potential is triggered, the membrane potential abruptly shoots upward and then equally abruptly shoots back downward, often ending below the resting level, where it remains for some period of time. The shape of the action potential is stereotyped; this means that the rise and fall usually have approximately the same amplitude and time course for all action potentials in a given cell. (Exceptions are discussed later in the article). In most neurons, the entire process takes place in about a thousandth of a second. Many types of neurons emit action potentials constantly at rates of up to 10–100 per second. However, some types are much quieter, and may go for minutes or longer without emitting any action potentials.


title: Action potential

text: Action potentials result from the presence in a cell's membrane of special types of voltage-gated ion channels. A voltage-gated ion channel is a transmembrane protein that has three key properties:


title: Action potential

text: Thus, a voltage-gated ion channel tends to be open for some values of the membrane potential, and closed for others. In most cases, however, the relationship between membrane potential and channel state is probabilistic and involves a time delay. Ion channels switch between conformations at unpredictable times: The membrane potential determines the rate of transitions and the probability per unit time of each type of transition.


title: Action potential

text: Voltage-gated ion channels are capable of producing action potentials because they can give rise to positive feedback loops: The membrane potential controls the state of the ion channels, but the state of the ion channels controls the membrane potential. Thus, in some situations, a rise in the membrane potential can cause ion channels to open, thereby causing a further rise in the membrane potential. An action potential occurs when this positive feedback cycle (Hodgkin cycle) proceeds explosively. The time and amplitude trajectory of the action potential are determined by the biophysical properties of the voltage-gated ion channels that produce it. Several types of channels capable of producing the positive feedback necessary to generate an action potential do exist. Voltage-gated sodium channels are responsible for the fast action potentials involved in nerve conduction. Slower action potentials in muscle cells and some types of neurons are generated by voltage-gated calcium channels. Each of these types comes in multiple variants, with different voltage sensitivity and different temporal dynamics.


title: Action potential

text: The most intensively studied type of voltage-dependent ion channels comprises the sodium channels involved in fast nerve conduction. These are sometimes known as Hodgkin-Huxley sodium channels because they were first characterized by Alan Hodgkin and Andrew Huxley in their Nobel Prize-winning studies of the biophysics of the action potential, but can more conveniently be referred to as "Na" channels. (The "V" stands for "voltage".) An "Na" channel has three possible states, known as "deactivated", "activated", and "inactivated". The channel is permeable only to sodium ions when it is in the "activated" state. When the membrane potential is low, the channel spends most of its time in the "deactivated" (closed) state. If the membrane potential is raised above a certain level, the channel shows increased probability of transitioning to the "activated" (open) state. The higher the membrane potential the greater the probability of activation. Once a channel has activated, it will eventually transition to the "inactivated" (closed) state. It tends then to stay inactivated for some time, but, if the membrane potential becomes low again, the channel will eventually transition back to the "deactivated" state. During an action potential, most channels of this type go through a cycle "deactivated"→"activated"→"inactivated"→"deactivated". This is only the population average behavior, however – an individual channel can in principle make any transition at any time. However, the likelihood of a channel's transitioning from the "inactivated" state directly to the "activated" state is very low: A channel in the "inactivated" state is refractory until it has transitioned back to the "deactivated" state.


title: Action potential

text: The outcome of all this is that the kinetics of the "Na" channels are governed by a transition matrix whose rates are voltage-dependent in a complicated way. Since these channels themselves play a major role in determining the voltage, the global dynamics of the system can be quite difficult to work out. Hodgkin and Huxley approached the problem by developing a set of differential equations for the parameters that govern the ion channel states, known as the Hodgkin-Huxley equations. These equations have been extensively modified by later research, but form the starting point for most theoretical studies of action potential biophysics.


title: Action potential

text: As the membrane potential is increased, sodium ion channels open, allowing the entry of sodium ions into the cell. This is followed by the opening of potassium ion channels that permit the exit of potassium ions from the cell. The inward flow of sodium ions increases the concentration of positively charged cations in the cell and causes depolarization, where the potential of the cell is higher than the cell's resting potential. The sodium channels close at the peak of the action potential, while potassium continues to leave the cell. The efflux of potassium ions decreases the membrane potential or hyperpolarizes the cell. For small voltage increases from rest, the potassium current exceeds the sodium current and the voltage returns to its normal resting value, typically −70 mV. However, if the voltage increases past a critical threshold, typically 15 mV higher than the resting value, the sodium current dominates. This results in a runaway condition whereby the positive feedback from the sodium current activates even more sodium channels. Thus, the cell "fires", producing an action potential. The frequency at which a neuron elicits action potentials is often referred to as a firing rate or neural firing rate.


title: Action potential

text: Currents produced by the opening of voltage-gated channels in the course of an action potential are typically significantly larger than the initial stimulating current. Thus, the amplitude, duration, and shape of the action potential are determined largely by the properties of the excitable membrane and not the amplitude or duration of the stimulus. This all-or-nothing property of the action potential sets it apart from graded potentials such as receptor potentials, electrotonic potentials, subthreshold membrane potential oscillations, and synaptic potentials, which scale with the magnitude of the stimulus. A variety of action potential types exist in many cell types and cell compartments as determined by the types of voltage-gated channels, leak channels, channel distributions, ionic concentrations, membrane capacitance, temperature, and other factors.


title: Action potential

text: The principal ions involved in an action potential are sodium and potassium cations; sodium ions enter the cell, and potassium ions leave, restoring equilibrium. Relatively few ions need to cross the membrane for the membrane voltage to change drastically. The ions exchanged during an action potential, therefore, make a negligible change in the interior and exterior ionic concentrations. The few ions that do cross are pumped out again by the continuous action of the sodium–potassium pump, which, with other ion transporters, maintains the normal ratio of ion concentrations across the membrane. Calcium cations and chloride anions are involved in a few types of action potentials, such as the cardiac action potential and the action potential in the single-cell alga "Acetabularia", respectively.


title: Action potential

text: Although action potentials are generated locally on patches of excitable membrane, the resulting currents can trigger action potentials on neighboring stretches of membrane, precipitating a domino-like propagation. In contrast to passive spread of electric potentials (electrotonic potential), action potentials are generated anew along excitable stretches of membrane and propagate without decay. Myelinated sections of axons are not excitable and do not produce action potentials and the signal is propagated passively as electrotonic potential. Regularly spaced unmyelinated patches, called the nodes of Ranvier, generate action potentials to boost the signal. Known as saltatory conduction, this type of signal propagation provides a favorable tradeoff of signal velocity and axon diameter. Depolarization of axon terminals, in general, triggers the release of neurotransmitter into the synaptic cleft. In addition, backpropagating action potentials have been recorded in the dendrites of pyramidal neurons, which are ubiquitous in the neocortex. These are thought to have a role in spike-timing-dependent plasticity.


title: Action potential

text: In the Hodgkin–Huxley membrane capacitance model, the speed of transmission of an action potential was undefined and it was assumed that adjacent areas became depolarized due to released ion interference with neighbouring channels. Measurements of ion diffusion and radii have since shown this not to be possible. Moreover, contradictory measurements of entropy changes and timing disputed the capacitance model as acting alone. Alternatively, Gilbert Ling's adsorption hypothesis, posits that the membrane potential and action potential of a living cell is due to the adsorption of mobile ions onto adsorption sites of cells.


title: Action potential

text: A neuron's ability to generate and propagate an action potential changes during development. How much the membrane potential of a neuron changes as the result of a current impulse is a function of the membrane input resistance. As a cell grows, more channels are added to the membrane, causing a decrease in input resistance. A mature neuron also undergoes shorter changes in membrane potential in response to synaptic currents. Neurons from a ferret lateral geniculate nucleus have a longer time constant and larger voltage deflection at P0 than they do at P30. One consequence of the decreasing action potential duration is that the fidelity of the signal can be preserved in response to high frequency stimulation. Immature neurons are more prone to synaptic depression than potentiation after high frequency stimulation.


title: Action potential

text: In the early development of many organisms, the action potential is actually initially carried by calcium current rather than sodium current. The opening and closing kinetics of calcium channels during development are slower than those of the voltage-gated sodium channels that will carry the action potential in the mature neurons. The longer opening times for the calcium channels can lead to action potentials that are considerably slower than those of mature neurons. Xenopus neurons initially have action potentials that take 60–90 ms. During development, this time decreases to 1 ms. There are two reasons for this drastic decrease. First, the inward current becomes primarily carried by sodium channels. Second, the delayed rectifier, a potassium channel current, increases to 3.5 times its initial strength.


title: Action potential

text: In order for the transition from a calcium-dependent action potential to a sodium-dependent action potential to proceed new channels must be added to the membrane. If Xenopus neurons are grown in an environment with RNA synthesis or protein synthesis inhibitors that transition is prevented. Even the electrical activity of the cell itself may play a role in channel expression. If action potentials in Xenopus myocytes are blocked, the typical increase in sodium and potassium current density is prevented or delayed.


title: Action potential

text: This maturation of electrical properties is seen across species. Xenopus sodium and potassium currents increase drastically after a neuron goes through its final phase of mitosis. The sodium current density of rat cortical neurons increases by 600% within the first two postnatal weeks.


title: Action potential

text: Several types of cells support an action potential, such as plant cells, muscle cells, and the specialized cells of the heart (in which occurs the cardiac action potential). However, the main excitable cell is the neuron, which also has the simplest mechanism for the action potential.


title: Action potential

text: Neurons are electrically excitable cells composed, in general, of one or more dendrites, a single soma, a single axon and one or more axon terminals. Dendrites are cellular projections whose primary function is to receive synaptic signals. Their protrusions, known as dendritic spines, are designed to capture the neurotransmitters released by the presynaptic neuron. They have a high concentration of ligand-gated ion channels. These spines have a thin neck connecting a bulbous protrusion to the dendrite. This ensures that changes occurring inside the spine are less likely to affect the neighboring spines. The dendritic spine can, with rare exception (see LTP), act as an independent unit. The dendrites extend from the soma, which houses the nucleus, and many of the "normal" eukaryotic organelles. Unlike the spines, the surface of the soma is populated by voltage activated ion channels. These channels help transmit the signals generated by the dendrites. Emerging out from the soma is the axon hillock. This region is characterized by having a very high concentration of voltage-activated sodium channels. In general, it is considered to be the spike initiation zone for action potentials, i.e. the trigger zone. Multiple signals generated at the spines, and transmitted by the soma all converge here. Immediately after the axon hillock is the axon. This is a thin tubular protrusion traveling away from the soma. The axon is insulated by a myelin sheath. Myelin is composed of either Schwann cells (in the peripheral nervous system) or oligodendrocytes (in the central nervous system), both of which are types of glial cells. Although glial cells are not involved with the transmission of electrical signals, they communicate and provide important biochemical support to neurons. To be specific, myelin wraps multiple times around the axonal segment, forming a thick fatty layer that prevents ions from entering or escaping the axon. This insulation prevents significant signal decay as well as ensuring faster signal speed. This insulation, however, has the restriction that no channels can be present on the surface of the axon. There are, therefore, regularly spaced patches of membrane, which have no insulation. These nodes of Ranvier can be considered to be "mini axon hillocks", as their purpose is to boost the signal in order to prevent significant signal decay. At the furthest end, the axon loses its insulation and begins to branch into several axon terminals. These presynaptic terminals, or synaptic boutons, are a specialized area within the axon of the presynaptic cell that contains neurotransmitters enclosed in small membrane-bound spheres called synaptic vesicles.


title: Action potential

text: Before considering the propagation of action potentials along axons and their termination at the synaptic knobs, it is helpful to consider the methods by which action potentials can be initiated at the axon hillock. The basic requirement is that the membrane voltage at the hillock be raised above the threshold for firing. There are several ways in which this depolarization can occur.


title: Action potential

text: Action potentials are most commonly initiated by excitatory postsynaptic potentials from a presynaptic neuron. Typically, neurotransmitter molecules are released by the presynaptic neuron. These neurotransmitters then bind to receptors on the postsynaptic cell. This binding opens various types of ion channels. This opening has the further effect of changing the local permeability of the cell membrane and, thus, the membrane potential. If the binding increases the voltage (depolarizes the membrane), the synapse is excitatory. If, however, the binding decreases the voltage (hyperpolarizes the membrane), it is inhibitory. Whether the voltage is increased or decreased, the change propagates passively to nearby regions of the membrane (as described by the cable equation and its refinements). Typically, the voltage stimulus decays exponentially with the distance from the synapse and with time from the binding of the neurotransmitter. Some fraction of an excitatory voltage may reach the axon hillock and may (in rare cases) depolarize the membrane enough to provoke a new action potential. More typically, the excitatory potentials from several synapses must work together at nearly the same time to provoke a new action potential. Their joint efforts can be thwarted, however, by the counteracting inhibitory postsynaptic potentials.


title: Action potential

text: Neurotransmission can also occur through electrical synapses. Due to the direct connection between excitable cells in the form of gap junctions, an action potential can be transmitted directly from one cell to the next in either direction. The free flow of ions between cells enables rapid non-chemical-mediated transmission. Rectifying channels ensure that action potentials move only in one direction through an electrical synapse. Electrical synapses are found in all nervous systems, including the human brain, although they are a distinct minority.


title: Action potential

text: The amplitude of an action potential is often thought to be independent of the amount of current that produced it. In other words, larger currents do not create larger action potentials. Therefore, action potentials are said to be all-or-none signals, since either they occur fully or they do not occur at all. This is in contrast to receptor potentials, whose amplitudes are dependent on the intensity of a stimulus. In both cases, the frequency of action potentials is correlated with the intensity of a stimulus.


title: Action potential

text: Despite the classical view of the action potential as a stereotyped, uniform signal having dominated the field of neuroscience for many decades, newer evidence does suggest that action potentials are more complex events indeed capable of transmitting information through not just their amplitude, but their duration and phase as well, sometimes even up to distances originally not thought to be possible.


title: Action potential

text: In sensory neurons, an external signal such as pressure, temperature, light, or sound is coupled with the opening and closing of ion channels, which in turn alter the ionic permeabilities of the membrane and its voltage. These voltage changes can again be excitatory (depolarizing) or inhibitory (hyperpolarizing) and, in some sensory neurons, their combined effects can depolarize the axon hillock enough to provoke action potentials. Some examples in humans include the olfactory receptor neuron and Meissner's corpuscle, which are critical for the sense of smell and touch, respectively. However, not all sensory neurons convert their external signals into action potentials; some do not even have an axon. Instead, they may convert the signal into the release of a neurotransmitter, or into continuous graded potentials, either of which may stimulate subsequent neuron(s) into firing an action potential. For illustration, in the human ear, hair cells convert the incoming sound into the opening and closing of mechanically gated ion channels, which may cause neurotransmitter molecules to be released. In similar manner, in the human retina, the initial photoreceptor cells and the next layer of cells (comprising bipolar cells and horizontal cells) do not produce action potentials; only some amacrine cells and the third layer, the ganglion cells, produce action potentials, which then travel up the optic nerve.


title: Action potential

text: In sensory neurons, action potentials result from an external stimulus. However, some excitable cells require no such stimulus to fire: They spontaneously depolarize their axon hillock and fire action potentials at a regular rate, like an internal clock. The voltage traces of such cells are known as pacemaker potentials. The cardiac pacemaker cells of the sinoatrial node in the heart provide a good example. Although such pacemaker potentials have a natural rhythm, it can be adjusted by external stimuli; for instance, heart rate can be altered by pharmaceuticals as well as signals from the sympathetic and parasympathetic nerves. The external stimuli do not cause the cell's repetitive firing, but merely alter its timing. In some cases, the regulation of frequency can be more complex, leading to patterns of action potentials, such as bursting.


title: Action potential

text: The course of the action potential can be divided into five parts: the rising phase, the peak phase, the falling phase, the undershoot phase, and the refractory period. During the rising phase the membrane potential depolarizes (becomes more positive). The point at which depolarization stops is called the peak phase. At this stage, the membrane potential reaches a maximum. Subsequent to this, there is a falling phase. During this stage the membrane potential becomes more negative, returning towards resting potential. The undershoot, or afterhyperpolarization, phase is the period during which the membrane potential temporarily becomes more negatively charged than when at rest (hyperpolarized). Finally, the time during which a subsequent action potential is impossible or difficult to fire is called the refractory period, which may overlap with the other phases.


title: Action potential

text: The course of the action potential is determined by two coupled effects. First, voltage-sensitive ion channels open and close in response to changes in the membrane voltage "V". This changes the membrane's permeability to those ions. Second, according to the Goldman equation, this change in permeability changes the equilibrium potential "E", and, thus, the membrane voltage "V". Thus, the membrane potential affects the permeability, which then further affects the membrane potential. This sets up the possibility for positive feedback, which is a key part of the rising phase of the action potential. A complicating factor is that a single ion channel may have multiple internal "gates" that respond to changes in "V" in opposite ways, or at different rates. For example, although raising "V" "opens" most gates in the voltage-sensitive sodium channel, it also "closes" the channel's "inactivation gate", albeit more slowly. Hence, when "V" is raised suddenly, the sodium channels open initially, but then close due to the slower inactivation.


title: Action potential

text: The voltages and currents of the action potential in all of its phases were modeled accurately by Alan Lloyd Hodgkin and Andrew Huxley in 1952, for which they were awarded the Nobel Prize in Physiology or Medicine in 1963. However, their model considers only two types of voltage-sensitive ion channels, and makes several assumptions about them, e.g., that their internal gates open and close independently of one another. In reality, there are many types of ion channels, and they do not always open and close independently.


title: Action potential

text: A typical action potential begins at the axon hillock with a sufficiently strong depolarization, e.g., a stimulus that increases "V". This depolarization is often caused by the injection of extra sodium cations into the cell; these cations can come from a wide variety of sources, such as chemical synapses, sensory neurons or pacemaker potentials.


title: Action potential

text: For a neuron at rest, there is a high concentration of sodium and chloride ions in the extracellular fluid compared to the intracellular fluid, while there is a high concentration of potassium ions in the intracellular fluid compared to the extracellular fluid. The difference in concentrations, which causes ions to move from a high to a low concentration, and electrostatic effects (attraction of opposite charges) are responsible for the movement of ions in and out of the neuron. The inside of a neuron has a negative charge, relative to the cell exterior, from the movement of K out of the cell. The neuron membrane is more permeable to K than to other ions, allowing this ion to selectively move out of the cell, down its concentration gradient. This concentration gradient along with potassium leak channels present on the membrane of the neuron causes an efflux of potassium ions making the resting potential close to "E" ≈ –75 mV. Since Na ions are in higher concentrations outside of the cell, the concentration and voltage differences both drive them into the cell when Na channels open. Depolarization opens both the sodium and potassium channels in the membrane, allowing the ions to flow into and out of the axon, respectively. If the depolarization is small (say, increasing "V" from −70 mV to −60 mV), the outward potassium current overwhelms the inward sodium current and the membrane repolarizes back to its normal resting potential around −70 mV. However, if the depolarization is large enough, the inward sodium current increases more than the outward potassium current and a runaway condition (positive feedback) results: the more inward current there is, the more "V" increases, which in turn further increases the inward current. A sufficiently strong depolarization (increase in "V") causes the voltage-sensitive sodium channels to open; the increasing permeability to sodium drives "V" closer to the sodium equilibrium voltage "E"≈ +55 mV. The increasing voltage in turn causes even more sodium channels to open, which pushes "V" still further towards "E". This positive feedback continues until the sodium channels are fully open and "V" is close to "E". The sharp rise in "V" and sodium permeability correspond to the "rising phase" of the action potential.


title: Action potential

text: The critical threshold voltage for this runaway condition is usually around −45 mV, but it depends on the recent activity of the axon. A cell that has just fired an action potential cannot fire another one immediately, since the Na channels have not recovered from the inactivated state. The period during which no new action potential can be fired is called the "absolute refractory period". At longer times, after some but not all of the ion channels have recovered, the axon can be stimulated to produce another action potential, but with a higher threshold, requiring a much stronger depolarization, e.g., to −30 mV. The period during which action potentials are unusually difficult to evoke is called the "relative refractory period".


title: Action potential

text: The positive feedback of the rising phase slows and comes to a halt as the sodium ion channels become maximally open. At the peak of the action potential, the sodium permeability is maximized and the membrane voltage "V" is nearly equal to the sodium equilibrium voltage "E". However, the same raised voltage that opened the sodium channels initially also slowly shuts them off, by closing their pores; the sodium channels become "inactivated". This lowers the membrane's permeability to sodium relative to potassium, driving the membrane voltage back towards the resting value. At the same time, the raised voltage opens voltage-sensitive potassium channels; the increase in the membrane's potassium permeability drives "V" towards "E". Combined, these changes in sodium and potassium permeability cause "V" to drop quickly, repolarizing the membrane and producing the "falling phase" of the action potential.


title: Action potential

text: The depolarized voltage opens additional voltage-dependent potassium channels, and some of these do not close right away when the membrane returns to its normal resting voltage. In addition, further potassium channels open in response to the influx of calcium ions during the action potential. The intracellular concentration of potassium ions is transiently unusually low, making the membrane voltage "V" even closer to the potassium equilibrium voltage "E". The membrane potential goes below the resting membrane potential. Hence, there is an undershoot or hyperpolarization, termed an afterhyperpolarization, that persists until the membrane potassium permeability returns to its usual value, restoring the membrane potential to the resting state.


title: Action potential

text: Each action potential is followed by a refractory period, which can be divided into an "absolute refractory period", during which it is impossible to evoke another action potential, and then a "relative refractory period", during which a stronger-than-usual stimulus is required. These two refractory periods are caused by changes in the state of sodium and potassium channel molecules. When closing after an action potential, sodium channels enter an "inactivated" state, in which they cannot be made to open regardless of the membrane potential—this gives rise to the absolute refractory period. Even after a sufficient number of sodium channels have transitioned back to their resting state, it frequently happens that a fraction of potassium channels remains open, making it difficult for the membrane potential to depolarize, and thereby giving rise to the relative refractory period. Because the density and subtypes of potassium channels may differ greatly between different types of neurons, the duration of the relative refractory period is highly variable.


title: Action potential

text: The absolute refractory period is largely responsible for the unidirectional propagation of action potentials along axons. At any given moment, the patch of axon behind the actively spiking part is refractory, but the patch in front, not having been activated recently, is capable of being stimulated by the depolarization from the action potential.


title: Action potential

text: The action potential generated at the axon hillock propagates as a wave along the axon. The currents flowing inwards at a point on the axon during an action potential spread out along the axon, and depolarize the adjacent sections of its membrane. If sufficiently strong, this depolarization provokes a similar action potential at the neighboring membrane patches. This basic mechanism was demonstrated by Alan Lloyd Hodgkin in 1937. After crushing or cooling nerve segments and thus blocking the action potentials, he showed that an action potential arriving on one side of the block could provoke another action potential on the other, provided that the blocked segment was sufficiently short.


title: Action potential

text: Once an action potential has occurred at a patch of membrane, the membrane patch needs time to recover before it can fire again. At the molecular level, this "absolute refractory period" corresponds to the time required for the voltage-activated sodium channels to recover from inactivation, i.e., to return to their closed state. There are many types of voltage-activated potassium channels in neurons. Some of them inactivate fast (A-type currents) and some of them inactivate slowly or not inactivate at all; this variability guarantees that there will be always an available source of current for repolarization, even if some of the potassium channels are inactivated because of preceding depolarization. On the other hand, all neuronal voltage-activated sodium channels inactivate within several milliseconds during strong depolarization, thus making following depolarization impossible until a substantial fraction of sodium channels have returned to their closed state. Although it limits the frequency of firing, the absolute refractory period ensures that the action potential moves in only one direction along an axon. The currents flowing in due to an action potential spread out in both directions along the axon. However, only the unfired part of the axon can respond with an action potential; the part that has just fired is unresponsive until the action potential is safely out of range and cannot restimulate that part. In the usual orthodromic conduction, the action potential propagates from the axon hillock towards the synaptic knobs (the axonal termini); propagation in the opposite direction—known as antidromic conduction—is very rare. However, if a laboratory axon is stimulated in its middle, both halves of the axon are "fresh", i.e., unfired; then two action potentials will be generated, one traveling towards the axon hillock and the other traveling towards the synaptic knobs.


title: Action potential

text: In order to enable fast and efficient transduction of electrical signals in the nervous system, certain neuronal axons are covered with myelin sheaths. Myelin is a multilamellar membrane that enwraps the axon in segments separated by intervals known as nodes of Ranvier. It is produced by specialized cells: Schwann cells exclusively in the peripheral nervous system, and oligodendrocytes exclusively in the central nervous system. Myelin sheath reduces membrane capacitance and increases membrane resistance in the inter-node intervals, thus allowing a fast, saltatory movement of action potentials from node to node. Myelination is found mainly in vertebrates, but an analogous system has been discovered in a few invertebrates, such as some species of shrimp. Not all neurons in vertebrates are myelinated; for example, axons of the neurons comprising the autonomous nervous system are not, in general, myelinated.


title: Action potential

text: Myelin prevents ions from entering or leaving the axon along myelinated segments. As a general rule, myelination increases the conduction velocity of action potentials and makes them more energy-efficient. Whether saltatory or not, the mean conduction velocity of an action potential ranges from 1 meter per second (m/s) to over 100 m/s, and, in general, increases with axonal diameter.


title: Action potential

text: Action potentials cannot propagate through the membrane in myelinated segments of the axon. However, the current is carried by the cytoplasm, which is sufficient to depolarize the first or second subsequent node of Ranvier. Instead, the ionic current from an action potential at one node of Ranvier provokes another action potential at the next node; this apparent "hopping" of the action potential from node to node is known as saltatory conduction. Although the mechanism of saltatory conduction was suggested in 1925 by Ralph Lillie, the first experimental evidence for saltatory conduction came from Ichiji Tasaki and Taiji Takeuchi and from Andrew Huxley and Robert Stämpfli. By contrast, in unmyelinated axons, the action potential provokes another in the membrane immediately adjacent, and moves continuously down the axon like a wave.


title: Action potential

text: Myelin has two important advantages: fast conduction speed and energy efficiency. For axons larger than a minimum diameter (roughly 1 micrometre), myelination increases the conduction velocity of an action potential, typically tenfold. Conversely, for a given conduction velocity, myelinated fibers are smaller than their unmyelinated counterparts. For example, action potentials move at roughly the same speed (25 m/s) in a myelinated frog axon and an unmyelinated squid giant axon, but the frog axon has a roughly 30-fold smaller diameter and 1000-fold smaller cross-sectional area. Also, since the ionic currents are confined to the nodes of Ranvier, far fewer ions "leak" across the membrane, saving metabolic energy. This saving is a significant selective advantage, since the human nervous system uses approximately 20% of the body's metabolic energy.


title: Action potential

text: The length of axons' myelinated segments is important to the success of saltatory conduction. They should be as long as possible to maximize the speed of conduction, but not so long that the arriving signal is too weak to provoke an action potential at the next node of Ranvier. In nature, myelinated segments are generally long enough for the passively propagated signal to travel for at least two nodes while retaining enough amplitude to fire an action potential at the second or third node. Thus, the safety factor of saltatory conduction is high, allowing transmission to bypass nodes in case of injury. However, action potentials may end prematurely in certain places where the safety factor is low, even in unmyelinated neurons; a common example is the branch point of an axon, where it divides into two axons.


title: Action potential

text: Some diseases degrade myelin and impair saltatory conduction, reducing the conduction velocity of action potentials. The most well-known of these is multiple sclerosis, in which the breakdown of myelin impairs coordinated movement.


title: Action potential

text: The flow of currents within an axon can be described quantitatively by cable theory and its elaborations, such as the compartmental model. Cable theory was developed in 1855 by Lord Kelvin to model the transatlantic telegraph cable and was shown to be relevant to neurons by Hodgkin and Rushton in 1946. In simple cable theory, the neuron is treated as an electrically passive, perfectly cylindrical transmission cable, which can be described by a partial differential equation


title: Action potential

text: where "V"("x", "t") is the voltage across the membrane at a time "t" and a position "x" along the length of the neuron, and where λ and τ are the characteristic length and time scales on which those voltages decay in response to a stimulus. Referring to the circuit diagram on the right, these scales can be determined from the resistances and capacitances per unit length.


title: Action potential

text: These time and length-scales can be used to understand the dependence of the conduction velocity on the diameter of the neuron in unmyelinated fibers. For example, the time-scale τ increases with both the membrane resistance "r" and capacitance "c". As the capacitance increases, more charge must be transferred to produce a given transmembrane voltage (by the equation "Q" = "CV"); as the resistance increases, less charge is transferred per unit time, making the equilibration slower. In a similar manner, if the internal resistance per unit length "r" is lower in one axon than in another (e.g., because the radius of the former is larger), the spatial decay length λ becomes longer and the conduction velocity of an action potential should increase. If the transmembrane resistance "r" is increased, that lowers the average "leakage" current across the membrane, likewise causing "λ" to become longer, increasing the conduction velocity.


title: Action potential

text: In general, action potentials that reach the synaptic knobs cause a neurotransmitter to be released into the synaptic cleft. Neurotransmitters are small molecules that may open ion channels in the postsynaptic cell; most axons have the same neurotransmitter at all of their termini. The arrival of the action potential opens voltage-sensitive calcium channels in the presynaptic membrane; the influx of calcium causes vesicles filled with neurotransmitter to migrate to the cell's surface and release their contents into the synaptic cleft. This complex process is inhibited by the neurotoxins tetanospasmin and botulinum toxin, which are responsible for tetanus and botulism, respectively.


title: Action potential

text: Some synapses dispense with the "middleman" of the neurotransmitter, and connect the presynaptic and postsynaptic cells together. When an action potential reaches such a synapse, the ionic currents flowing into the presynaptic cell can cross the barrier of the two cell membranes and enter the postsynaptic cell through pores known as connexons. Thus, the ionic currents of the presynaptic action potential can directly stimulate the postsynaptic cell. Electrical synapses allow for faster transmission because they do not require the slow diffusion of neurotransmitters across the synaptic cleft. Hence, electrical synapses are used whenever fast response and coordination of timing are crucial, as in escape reflexes, the retina of vertebrates, and the heart.


title: Action potential

text: A special case of a chemical synapse is the neuromuscular junction, in which the axon of a motor neuron terminates on a muscle fiber. In such cases, the released neurotransmitter is acetylcholine, which binds to the acetylcholine receptor, an integral membrane protein in the membrane (the "sarcolemma") of the muscle fiber. However, the acetylcholine does not remain bound; rather, it dissociates and is hydrolyzed by the enzyme, acetylcholinesterase, located in the synapse. This enzyme quickly reduces the stimulus to the muscle, which allows the degree and timing of muscular contraction to be regulated delicately. Some poisons inactivate acetylcholinesterase to prevent this control, such as the nerve agents sarin and tabun, and the insecticides diazinon and malathion.


title: Action potential

text: The cardiac action potential differs from the neuronal action potential by having an extended plateau, in which the membrane is held at a high voltage for a few hundred milliseconds prior to being repolarized by the potassium current as usual. This plateau is due to the action of slower calcium channels opening and holding the membrane voltage near their equilibrium potential even after the sodium channels have inactivated.


title: Action potential

text: The cardiac action potential plays an important role in coordinating the contraction of the heart. The cardiac cells of the sinoatrial node provide the pacemaker potential that synchronizes the heart. The action potentials of those cells propagate to and through the atrioventricular node (AV node), which is normally the only conduction pathway between the atria and the ventricles. Action potentials from the AV node travel through the bundle of His and thence to the Purkinje fibers. Conversely, anomalies in the cardiac action potential—whether due to a congenital mutation or injury—can lead to human pathologies, especially arrhythmias. Several anti-arrhythmia drugs act on the cardiac action potential, such as quinidine, lidocaine, beta blockers, and verapamil.


title: Action potential

text: The action potential in a normal skeletal muscle cell is similar to the action potential in neurons. Action potentials result from the depolarization of the cell membrane (the sarcolemma), which opens voltage-sensitive sodium channels; these become inactivated and the membrane is repolarized through the outward current of potassium ions. The resting potential prior to the action potential is typically −90mV, somewhat more negative than typical neurons. The muscle action potential lasts roughly 2–4 ms, the absolute refractory period is roughly 1–3 ms, and the conduction velocity along the muscle is roughly 5 m/s. The action potential releases calcium ions that free up the tropomyosin and allow the muscle to contract. Muscle action potentials are provoked by the arrival of a pre-synaptic neuronal action potential at the neuromuscular junction, which is a common target for neurotoxins.


title: Action potential

text: Plant and fungal cells are also electrically excitable. The fundamental difference from animal action potentials is that the depolarization in plant cells is not accomplished by an uptake of positive sodium ions, but by release of negative "chloride" ions. In 1906, J. C. Bose published the first measurements of action potentials in plants, which had previously been discovered by Burdon-Sanderson and Darwin. An increase in cytoplasmic calcium ions may be the cause of anion release into the cell. This makes calcium a precursor to ion movements, such as the influx of negative chloride ions and efflux of positive potassium ions, as seen in barley leaves.


title: Action potential

text: The initial influx of calcium ions also poses a small cellular depolarization, causing the voltage-gated ion channels to open and allowing full depolarization to be propagated by chloride ions.


title: Action potential

text: Some plants (e.g. "Dionaea muscipula") use sodium-gated channels to operate movements and essentially "count". "Dionaea muscipula", also known as the Venus flytrap, is found in subtropical wetlands in North and South Carolina. When there are poor soil nutrients, the flytrap relies on a diet of insects and animals. Despite research on the plant, there lacks an understanding behind the molecular basis to the Venus flytraps, and carnivore plants in general.


title: Action potential

text: However, plenty of research has been done on action potentials and how they affect movement and clockwork within the Venus flytrap. To start, the resting membrane potential of the Venus flytrap (-120mV) is lower than animal cells (usually -90mV to -40mV). The lower resting potential makes it easier to activate an action potential. Thus, when an insect lands on the trap of the plant, it triggers a hair-like mechanoreceptor. This receptor then activates an action potential which lasts around 1.5 ms. Ultimately, this causes an increase of positive Calcium ions into the cell, slightly depolarizing it.


title: Action potential

text: However, the flytrap doesn't close after one trigger. Instead, it requires the activation of 2 or more hairs. If only one hair is triggered, it throws the activation as a false positive. Further, the second hair must be activated within a certain time interval (0.75 s - 40 s) for it to register with the first activation. Thus, a buildup of calcium starts and slowly falls from the first trigger. When the second action potential is fired within the time interval, it reaches the Calcium threshold to depolarize the cell, closing the trap on the prey within a fraction of a second.


title: Action potential

text: Together with the subsequent release of positive potassium ions the action potential in plants involves an osmotic loss of salt (KCl). Whereas, the animal action potential is osmotically neutral because equal amounts of entering sodium and leaving potassium cancel each other osmotically. The interaction of electrical and osmotic relations in plant cells appears to have arisen from an osmotic function of electrical excitability in a common unicellular ancestors of plants and animals under changing salinity conditions. Further, the present function of rapid signal transmission is seen as a newer accomplishment of metazoan cells in a more stable osmotic environment. It is likely that the familiar signaling function of action potentials in some vascular plants (e.g. "Mimosa pudica") arose independently from that in metazoan excitable cells.


title: Action potential

text: Unlike the rising phase and peak, the falling phase and after-hyperpolarization seem to depend primarily on cations that are not calcium. To initiate repolarization, the cell requires movement of potassium out of the cell through passive transportation on the membrane. This differs from neurons because the movement of potassium does not dominate the decrease in membrane potential; In fact, to fully repolarize, a plant cell requires energy in the form of ATP to assist in the release of hydrogen from the cell – utilizing a transporter commonly known as H+-ATPase.


title: Action potential

text: Action potentials are found throughout multicellular organisms, including plants, invertebrates such as insects, and vertebrates such as reptiles and mammals. Sponges seem to be the main phylum of multicellular eukaryotes that does not transmit action potentials, although some studies have suggested that these organisms have a form of electrical signaling, too. The resting potential, as well as the size and duration of the action potential, have not varied much with evolution, although the conduction velocity does vary dramatically with axonal diameter and myelination.


title: Action potential

text: Given its conservation throughout evolution, the action potential seems to confer evolutionary advantages. One function of action potentials is rapid, long-range signaling within the organism; the conduction velocity can exceed 110 m/s, which is one-third the speed of sound. For comparison, a hormone molecule carried in the bloodstream moves at roughly 8 m/s in large arteries. Part of this function is the tight coordination of mechanical events, such as the contraction of the heart. A second function is the computation associated with its generation. Being an all-or-none signal that does not decay with transmission distance, the action potential has similar advantages to digital electronics. The integration of various dendritic signals at the axon hillock and its thresholding to form a complex train of action potentials is another form of computation, one that has been exploited biologically to form central pattern generators and mimicked in artificial neural networks.


title: Action potential

text: The common prokaryotic/eukaryotic ancestor, which lived perhaps four billion years ago, is believed to have had voltage-gated channels. This functionality was likely, at some later point, cross-purposed to provide a communication mechanism. Even modern single-celled bacteria can utilize action potentials to communicate with other bacteria in the same biofilm.


title: Action potential

text: The study of action potentials has required the development of new experimental methods. The initial work, prior to 1955, was carried out primarily by Alan Lloyd Hodgkin and Andrew Fielding Huxley, who were, along John Carew Eccles, awarded the 1963 Nobel Prize in Physiology or Medicine for their contribution to the description of the ionic basis of nerve conduction. It focused on three goals: isolating signals from single neurons or axons, developing fast, sensitive electronics, and shrinking electrodes enough that the voltage inside a single cell could be recorded.


title: Action potential

text: The first problem was solved by studying the giant axons found in the neurons of the squid ("Loligo forbesii" and "Doryteuthis pealeii", at the time classified as "Loligo pealeii"). These axons are so large in diameter (roughly 1 mm, or 100-fold larger than a typical neuron) that they can be seen with the naked eye, making them easy to extract and manipulate. However, they are not representative of all excitable cells, and numerous other systems with action potentials have been studied.