由 xw » 7月 27 2011
不好意思，Reptilian Brain还没学通，就胡扯了两贴，按关中说就是跳舞了。小麦
喜欢跳舞，秋子是真跳。我也跳不好，还是重归正题，把脑干（原始脑）的第三块
medulla oblongata－－延髓整理一下。前面的贴子读之又读，消化了不少，不明
的地方更多，本也不该一下操之过急。周末还得去一次脑展，买些书与资料。至今
还没找到一本上好的书，乱读一气，多是初级入门书，有图有例，对我刚刚好。
Right below the swollen pons(意大利语，桥，源于一意教授名) is the medulla
oblongata. This long stretch of cord provides a pathway for motor signals
between the nerves in the spinal cord and the brain. It is the main center
of breathing and heart control, but it is also the place where activities
you can’t always control are taken care of — like swallowing, coughing,
gagging, and even vomitting.
延髓，又称延脑，为中央神经系统的一部分，是脑干最下方的结构，位于小脑正前方
。长约一寸半，阔约半寸。
它具有第九至第十二颅神经及多个神经束的核，在处理感觉及运动讯息传送有一定功
用。
延髓具有心血管中枢及呼吸中枢等重要维生中枢的结构及感应器，能藉此维持体内平
衡。此部份受伤或受压（如脑肿瘤）会危及生命。由于由不能再生的中央神经元组成
，故此部分受伤许多时都是致命的。
Section of the medulla oblongata at about the middle of the olive.
这图中的结构名词就有得理了，还是英中，或说拉中对照一下，慢慢理清：
medulla oblongata
- medullary pyramids
- Medullary cranial nerve nuclei
- Inferior salivatory nucleus
- Nucleus ambiguus
- Dorsal nucleus of vagus nerve
- Hypoglossal nucleus
- Solitary nucleus
前部/腹部: 延髓弓状核 • 延髓锥体 (锥体交叉) • 橄榄体 • 下橄榄核 • 延髓内前裂
• 延髓呼吸核团
后部/背部: 孤束核/孤束（VII，IX，X） • 舌下神经核（XII）, 迷走神经背核（X）
• 疑核（IX,X,XI） • 下泌涎核（IX） • 薄束核/楔束核/楔束副核 • 延髓最后区
• 延髓内侧沟 • 延髓呼吸核团
中缝/网状结构 感觉交叉 • 网状结构 (巨细胞核, 小细胞网状核, 腹侧网状核, 外侧
网状核, 旁正中网状核) • 中缝核群 (中缝隐核, 中缝大核, 中缝苍白核)
束 皮层脊髓束 (皮质脊髓侧束, 皮质脊髓前束) • 小脑下脚 • 橄榄小脑束 • 脊髓小
脑束 (脊髓小脑背侧束, 脊髓小脑腹侧束) • 脊髓丘脑束 • 后柱内侧丘系通路（PCML）
(后外侧弓状纤维, 内弓状纤维, 内侧丘系) • 锥体外系 (红核脊髓束, 前庭脊髓束,
顶盖脊髓束)
(Formatio reticularis grisea and formatio reticularis alba labeled at left.)
谈到网状结构，Reticular Formation：这一组神经元于脑干上下，不局限于哪个部
位。It’s like a filter for the thalamus（丘脑）, takes millions of sensory inputs
you get every second from all over your body – eyes, ears, nose, mouth,
figertips, skin — and let in only the important stuff.
Smelling: when you smell something sweet, spicy or stinky, your nose is
sensing chemicals in the air. It sends messages to a brain area called the
olfactory cortex, which can tell about 20,000 aromas apart.
Your eyes see by using tiny receptors called rods and cones. There are
more than five million cones and more than 120 million rods sending signals
to your brain. These signals tell your brain about everything you see,
from colors and shadows to movement and depth.
There are ten thousand taste buds in your mouth, mostly on your tongue.
Each one has fifty to one hundred and fifty receptors. That means that your
mouth can send more than a million signals to your brain while you’re eating
something.
Your ears capture sound waves and send them to your brain via a complex
system of small hairs and liquid. Neurons turn these waves into signals and
your brain identifies the signals as sounds.
Your hand has 17,000 receptors that give you your sense of touch. The skin
that covers your body has receptors along every inch of it, although not every
part is as sensitive as your hand.
Add all this up, and it means that your brain is receiving several hundred
million bits of information every second — even at this very moment. The
reticular formation sorts out what’s important and what’s not.
延髓下通Spinal Cord，脊髓，已冲出头脑的范围。这样我总算把Reptilian Brain蒙混
过去。沿进化发展的秩序，下一步应该是Limbic system，中文称脑缘，英文有名The
Mammalian Brain。
此前我想上溯一下谈真正源初动物的脑子，说有一种海生动物Sea squirt，海鞘，有
比较源初的脑，年轻时用来指挥游动直到找到自己中意的一块寄居地，此后就象石头
一样固定，脑子也不再使用。脑子留着干什么呢？还占空间，慢慢地被身体吞噬消化
掉了。这让我想到昆虫中的蚂蚁，蚂蚁原是有翅膀的，飞行到一乐土开疆立国，纷纷
兑退掉翅膀，有点项羽或科尔特斯的破斧沉舟的气质。
Some people say that sea squirt is “eating its own brain.” Getting rid of the
brain frees up room in the body for more feeding space…The brainless sea
squirt never misses its brain. It spends rest of life moving back and forth
in the ocean currents, appearing to wave to anyone who sees it. For this
reason, colonies of sea squirts are known as “dead man’s fingers.”
to be continued…
xw Blog 