The skeletal muscles move the limbs (arms and legs). They move the jaw up and down so that food can be chewed. Skeletal muscles are the only "voluntary" muscles, the only ones that we can choose to move.
The cardiac muscle is the muscle in the heart. When this muscle contracts it pushes blood through the circulatory system. The cardiac muscle is "not" voluntary.
The smooth muscles are the other muscles in the body that are involuntary. Smooth muscles are in many places. They are in:
Muscles are made of many muscle cells. The cells contract together to make the muscle get shorter. The muscle cells know to do this together because many of them get information sent to them by nerves. The cells that get the message from nerves tell other cells that are near them. They tell the other cells by sending an electrical current.
Muscle cells are filled with proteins called actin and myosin. These are the proteins that make the muscle contract (get shorter.)
When a nerve tells a muscle to contract, the muscle opens holes in its cell membrane. These holes are proteins that are called "calcium channels". The calcium ions rush into the cell. Calcium also comes out of a special place in the cell called the "sarcoplasmic reticulum". This calcium sticks to the specialized proteins actin and myosin. This triggers these proteins to contract the muscle.
Contraction also needs ATP. This is the energy that your cells use. It is made from using glucose in the cell. It takes a lot of energy to release contracted muscles. They use most of the energy for building muscles.
Exercise makes muscles get bigger (see hypertrophy). Exercise also makes muscles stronger. If a person does not exercise, their muscles become smaller and weaker. This is called muscle atrophy.
There are many different kinds of muscle diseases. There are three big groups of diseases:
Game Boy
The , is an 8-bit handheld video game console, first released in Japan in April 1989. It was later released in North America in July 1989 and then in Europe in September 1990. It is Nintendo's first handheld. The Game Boy is also the first portable console to use game cartridges, meaning the games are interchangeable. The Game Boy family eventually extended to include the Game Boy Color, Game Boy Advance, Game Boy Advance SP and Game Boy Micro.
The Game Boy has a green screen that displays four shades of dark green (gray for the Game Boy Pocket). Like the NES, the Game Boy has four buttons and a cross-shaped direction pad. The console has a single speaker, and it can be used with stereo headphones. As many as four Game Boys can be connected together with the Game Boy Link Cable.
The Game Boy was invented by Gunpei Yokoi, who also was responsible for creating the unsuccessful Virtual Boy and the successful Game & Watch games.
Recently, the Game Boy was compared to all Nintendo handhelds and systems released between 1989 and 2016 to see how long each one's battery life lasted, and the Game Boy beat all the other systems with 30 hours of battery life. The Game Boy provided the most game play at its time, and currently still does.
Stomach
The stomach is part of the digestive system. It is an internal organ between the esophagus and the small intestines. The stomach is the third stage in the digestive process. It holds food after ingestion. Food in the stomach then passes through to the small intestine where most of the food's nutrition is absorbed.
The stomach contains hydrochloric acid made by stomach cells. As a useful side-effect, the acid kills bacteria in the food. However, its main function is to help the protein-digesting enzymes called proteases work. In general, the food is churned, squeezed and mixed. This prepares it for digestion. The partially digested food is called chyme.
The stomach acid may cause problems. It can make peptic ulcers worse. It can also cause heartburn—pain in the chest when acid from the stomach "refluxes" (backs up into) the oesophagus. These can usually be treated by neutralizing the acid. Vomiting occurs when food goes back up the oesophagus and out the mouth. Vomiting can be a symptom of disease.
Stomachs of other mammals work differently to human stomachs. Ruminants, for example, have a stomach with multiple compartments.
In that system, food goes through the first part of the digestive system twice, and the work of digesting the grass is done by bacteria.
Other words for "stomach" include "belly" and "tummy".
Pain
Pain is a symptom of being hurt or sick. It is a bad sensation that is physical "and" emotional.
Most pain starts when part of the body is hurt. Nerves in that part send messages to the brain. Those messages tell the brain that the body is being damaged. Pain is not just the message the nerve sends to the brain. It is the bad emotion felt because of that damage.
The message that the nerve sends to the brain is called "nociception". What is experienced "because of" the nociception is pain.
Pain can be "acute" or "chronic". Acute means it only happens a short time. Chronic means the pain lasts a long time.
Pain can be from different types of injury:
Pain can also happen when there is no underlying injury or cause. Pain can happen just because the nerves do not work right. This is called "neuropathic" pain.
For most pain, the best treatment is to stop the damage that makes the pain. If the ankle is sprained, doctors tell the person not to walk on it. They tell them to put ice on it. This helps the injury stop. For an ulcer in the stomach, doctors stop the acid made in the stomach. This helps the ulcer to heal.
But many kinds of pain also need medicines to feel better. There are many different kinds of medicines for pain:
There are doctors who specialize in pain management. These are usually anesthesiologists but may also have any one of a number of underlying areas of specialization, such as neurology, physiatry, or internal medicine.
A new genetic method of treating chronic pain is in the research stage. The idea is to inactivate (turn off) gene HCN2, which plays a key role in chronic pain. Experiments on mice suggest this will work.
Drain
A drain is found in the ground and lets water go through (usually rainwater) to avoid the street or farmland getting flooded.
Super Mario 64
Super Mario 64 is a 1996 video game created by Nintendo for the Nintendo 64. The game was the first in the "Mario" series that used 3D graphics. Many fans and critics think that it is one of the best video games ever made.
Princess Peach makes a special cake and invites Mario to her castle in Mushroom Kingdom. As Mario arrives, he learns that Bowser took over the castle and kidnapped Peach. To defeat Bowser and rescue Peach, Mario enters each worlds on painting walls. The main hub of the game is Peach's castle. The player can unlock doors by collecting stars. There are 120 of them scattered among 15 maps and some secret maps. The player can get each of the stars by completing each of the achievements per level. One world requires two stars, for instance. Each locked door leads to more levels and challenges. Mario can also leave the castle and explore the small courtyard.
"Super Mario 64" was made in less than two years, but it was reported that Shigeru Miyamoto had thought about a 3D "Mario" game, called "Super Mario FX", five years before, while working on "Star Fox". Miyamoto came up with most of the ideas during the era of the Super Nintendo Entertainment System (SNES) and thought about using the Super FX chip to make it a SNES game, but decided to build it for the Nintendo 64 due to the SNES's technical limitations. On his Twitter Dylan Cuthbert stated that there was never a "Super Mario FX" game ever made, and that "Super Mario FX" was the internal code name of the FX chip.