松果體
Pineal gland

context: zh_tw: 松果腺細胞在很多非哺乳類的脊椎動物中非常地像眼睛的感光細胞。一些演化生物學家相信脊椎動物的松果體細胞與視網膜細胞共有一個同樣的演化原型。在一些脊椎動物中，曝曬在光線下可以啟動在松果體內的酵素連鎖反應以校正晝夜節律。一些早期的脊椎動物的顱骨化石有松果體孔。這與生理學中例如像七鰓鰻和喙頭蜥的現代「活化石」以及一些其他的脊椎動物所擁有的顱頂眼或所謂的「第三隻眼」有關，而在這些動物之中的一部份的顱頂眼具有感光功能。第三隻眼的存在代表著演化早期的視覺感受途徑。在喙頭蜥內的第三隻眼結構與角膜、晶狀體和視網膜類似，雖然其結構相似度還比較接近章魚而非脊椎動物的視網膜。其不對稱的整體由偏向左邊的「眼」及偏向右邊的松果體囊組成。「在含哺乳動物在內的失去顱頂眼的動物，松果囊被保留下來並壓縮成松果體的形式。」不像許多哺乳動物大腦的其餘部分，松果體並未被血腦障壁系統所隔離。它甚至擁有充沛的血流，僅次於腎。化石很少保留軟質的解剖結構。大約已有九千萬年歷史的俄羅斯梅羅瓦卡 (Melovatka) 鳥的大腦是個例外，並展現了一個遠超過預料之外的顱頂眼與松果體。在人類與其他的哺乳動物之中，從眼睛經由視網膜下視丘路徑系統到視叉上核與松果體的光線訊號對於晝夜節律是必須的。
en: Most living vertebrates have pineal glands. It is likely that the common ancestor of all vertebrates had a pair of photosensory organs on the top of its head, similar to the arrangement in modern lampreys. Some extinct Devonian fishes have two parietal foramina in their skulls, suggesting an ancestral bilaterality of parietal eyes. The parietal eye and the pineal gland of living tetrapods are probably the descendants of the left and right parts of this organ, respectively.During embryonic development, the parietal eye and the pineal organ of modern lizards and tuataras form together from a pocket formed in the brain ectoderm. The loss of parietal eyes in many living tetrapods is supported by developmental formation of a paired structure that subsequently fuses into a single pineal gland in developing embryos of turtles, snakes, birds, and mammals.The pineal organs of mammals fall into one of three categories based on shape. Rodents have more structurally-complex pineal glands than other mammals.Crocodilians and some tropical lineages of mammals (some xenarthrans (sloths), pangolins, sirenians (manatees & dugongs), and some marsupials (sugar gliders) have lost both their parietal eye and their pineal organ. Polar mammals, such as walruses and some seals, possess unusually large pineal glands.All amphibians have a pineal organ, but some frogs and toads also have what is called a "frontal organ", which is essentially a parietal eye.Pinealocytes in many non-mammalian vertebrates have a strong resemblance to the photoreceptor cells of the eye. Evidence from morphology and developmental biology suggests that pineal cells possess a common evolutionary ancestor with retinal cells.Pineal cytostructure seems to have evolutionary similarities to the retinal cells of the lateral eyes. Modern birds and reptiles express the phototransducing pigment melanopsin in the pineal gland. Avian pineal glands are thought to act like the suprachiasmatic nucleus in mammals. The structure of the pineal eye in modern lizards and tuatara is analogous to the cornea, lens, and retina of the lateral eyes of vertebrates.In most vertebrates, exposure to light sets off a chain reaction of enzymatic events within the pineal gland that regulates circadian rhythms. In humans and other mammals, the light signals necessary to set circadian rhythms are sent from the eye through the retinohypothalamic system to the suprachiasmatic nuclei (SCN) and the pineal gland.
qas: question: zh_tw: 在人和其它哺乳動物中，晝夜節律是從哪裡發出的？
en: Where are the circadian rhythms sent from in humans and other mammals?
answers: zh_tw: text: 眼睛
en: text: eye

context: zh_tw: 松果體最初被認為是某個較大的器官退化的殘留物。在 1917 年早期時，母牛的松果體萃取物被用來使青蛙的皮膚變亮。皮膚醫學教授艾倫・本生・勒納 (Aaron B. Lerner) 與他在耶魯大學的同事，在 1958 年時離析並命名了褪黑素，並希望這個來自松果體的物質能夠治療皮膚病。後來雖然這個物質並沒像預期般地有治療皮膚病的功用，但卻發現它有助於解決例如大鼠松果體的移除加快了其卵巢的成長、讓大鼠保持在不斷的日光下會減少他們松果體的重量以及松果體切除術 (pinealectomy) 和持續的日光兩者都對卵巢的成長有同樣程度的影響等不可思議的事實，這些知識促使了名為「時間生物學」的新領域出現。褪黑素是色胺酸這種胺基酸的衍生物，在中樞神經系統裡還有其他的功能。黑暗會刺激松果體對於褪黑素的分泌，反之光亮則會對其抑制。當視網膜的感光細胞偵測到光線並直接傳送訊號到視叉上核後，便產生了自然的晝夜節律。其過程是經從視叉上核投射到室旁核 (paraventricular nuclei) 的神經纖維傳達生理節奏的訊號到脊髓並經交感神經系統到頸上神經節 (superior cervical ganglia)，又從那裡傳到松果體。對於褪黑素在人體中的功能依然不太清楚，不過一般將它作為晝夜節律性睡眠障礙 (circadian rhythm sleep disorder) 的配藥。
en: The primary function of the pineal gland is to produce melatonin.  Melatonin has various functions in the central nervous system, the most important of which is to help modulate sleep patterns. Melatonin production is stimulated by darkness and inhibited by light. Light sensitive nerve cells in the retina detect light and send this signal to the suprachiasmatic nucleus (SCN), synchronizing the SCN to the day-night cycle. Nerve fibers then relay the daylight information from the SCN to the paraventricular nuclei (PVN), then to the spinal cord and via the sympathetic system to superior cervical ganglia (SCG), and from there into the pineal gland.
qas: question: zh_tw: 哪種細胞負責抑制白天的褪黑素分泌？
en: What type of cells are responsible for limiting melatonin production during the day?
answers: zh_tw: text: 松果體
en: text: Light sensitive nerve cells

question: zh_tw: 什麼會刺激褪黑素的產生？
en: What stimulates Melatonin production?
answers: zh_tw: text: 黑暗
en: text: darkness

question: zh_tw: 神經纖維在哪裡結束？
en: Where do nerve fibers end up?
answers: zh_tw: text: ganglia)，又從那裡傳到松果體。
en: text: pineal gland