脑（续一）
2023-04-16 19:27阅读：
DIENCEPHALON
The diencephalon, or inter
brain, is located between the cerebrum and the midbrain.
It is composed of a large structure at its upper end and a smaller
one below. The larger structure is the thalamus and the smaller
one, the hypothalamus.
间脑
间脑，或叫内脑，位于大脑与中脑之间。它是由上端的大结构和下端的较小结构组成。大结构是丘脑，而较小结构是下丘脑。
Thalamus. The thalamus lies next the
midline, divided from its twin on the opposite side by the THIRD
ventricle. Certain structures in the roof above it are known as the
epithalamus. Laterally, the thalamus fuses with the internal
capsule and the caudate nucleus, while below it joins with
sub-thalamus.
丘脑。丘脑位于中线附近，由第三脑室将其对边的双脑分开。顶部的某些结构被称为上丘脑。在侧面，丘脑与内囊和尾状核融合，而在下方与丘脑底部连接。
The thalamus is made up of many nuclei, connected to many
parts of the br
ain and spinal cord by sensory and motor fibers. It is an important
relay center and has its own functions as well.
丘脑由许多核组成，通过感觉和运动纤维与脑和脊髓的许多部分相连接。它是一个重要的中继中枢，它也有自己的功能。
All sensory impulses except the olfactory ones terminate in
the nuclei of the thalamus, and from there they are relayed to the
cortex. However, as the sensory impulses pass through the thalamus
they are integrated with one another. The thalamus receives crude
impulses of touch, temperature, and pain from lower areas. It then
fuses these sensations and modifies them so that when they are
received in the sensory cortex they are felt as a more complex
sensation. The thalamus also receives motor impulses from the
cerebellum and transmits them to the cortex. Impulses of pain are
the only sensory impulses that terminate in the thalamus, and it is
believed that the thalamus contains the body’s “pain center.” The
thalamus is also considered to be a center of consciousness, since
even a slight manipulation of this area during brain surgery
produces unconsciousness. (Because the brain itself does not feel
pain, many brain operations are performed with local anesthetics
and the patient remains conscious.)
除了嗅觉脉冲外，所有感觉脉冲都终止于丘脑核，并从那里传至大脑皮层。然而，当感觉脉冲通过丘脑时，它们彼此结合在一起。丘脑从较低区域接收来自触摸、温度以及疼痛的原始脉冲。然后它将这些这些感觉进行融合，并加以修改，因此当感觉皮层接收它们时，会感到它们是一种更复杂的感觉。丘脑还接收来自小脑的运动脉冲，并将它们传递到大脑皮层。疼痛脉冲是唯一终止于丘脑的感觉脉冲，人们认为丘脑包含了身体的“疼痛中枢”。丘脑也被认为是意识的中枢，因为在脑部手术中，即使是对这一区域的轻微操作都会导致无意识的情况发生。（因为，脑本身并无疼痛感，许多脑部手术都是在局部麻醉和患者依然清醒的状态下进行的）。
Hypothalamus. The
hypothalamus lies beneath the floor of the THIRD ventricle. From it
a bundle of nerve fibers enters the posterior lobe of the pituitary
gland (hypophysis). Like the thalamus, the hypothalamus is made of
many nuclear masses having many diverse functions. Most important
of these is its activity as the chief sub-cortical regulator of
both the sympathetic and parasympathetic nervous systems. The
anterior hypothalamus controls sympathetic responses. When
stimulated, the pupils dilate, the heart speeds up, the blood
pressure goes up, respiration increases, and the muscles become
overactive. However, if the posterior hypothalamus is
stimulated, the subject will experience abnormal sleepiness and
lethargy.
下丘脑。下丘脑位于第三脑室的底部。从这里一束神经纤维进入脑垂体（脑下垂体）的后叶。像丘脑一样，下丘脑由许多核团组成，拥有许多不同的功能。其中最重要的是它作为交感神经和副交感神经系统的主要皮层下调节器的活动。下丘脑前部控制着交感反应。当受到刺激时，瞳孔会放大，心跳加速，血压上升，呼吸增加，以及肌肉变得过于活跃。然而，如果下丘脑后部受到刺激，实验对象就会体验到异常的嗜睡和无精打采。
The hypothalamus also regulates the body’s water balance, the
metabolism of fats and carbohydrates, and serves as the body’s
“thermostat.” The anterior part the hypothalamus is sensitive to
temperature increase; if the body temperature rises too high, it
starts the body’s normal mechanisms for dissipating the excess
heat. The posterior part of the hypothalamus is sensitive to
decreased temperature; if the body becomes too cold it sets in
motion measures to increase the body temperature and conserve heat
loss.
下丘脑还控制着身体的水平衡、脂肪和碳水化合物的新陈代谢，并作为充当身体的“恒温器”。下丘脑的前部对温度增加很敏感；如果体温上升过高，它就开启身体散发多余热量的正常机制。下丘脑的后部对降温很敏感；如果身体变得过冷，它就启动措施来增加身体的温度，并避免热量流失。
Research has indicated that certain cells in the forward area
of the hypothalamus secrete a hormone that is conducted along axons
of these nerve cells to the posterior lobe of the pituitary gland.
This hormone is anti-diuretic, that is, it prevents the loss of
excess water from the kidneys. If these hormone-secreting cells are
destroyed, causing a loss of anti-diuretic hormone, there is a
great loss of water in the urine and an increased thirst. This
condition is known as diabetes insipidus.
研究表明，在下丘脑前部的某些细胞中会分泌一种引导沿着这些神经细胞的轴突至脑下垂体后叶的荷尔蒙。这种荷尔蒙是抗利尿的，换言之，它可防止肾脏流失过多的水分。如果这些泌荷尔蒙的细胞受到损害，导致抗利尿荷尔蒙流丧失，尿液中的水分会大量流失，口渴加剧。这种状态被称为尿崩症。
MIDBRAIN
The mesencephalon, or midbrain, is the smallest and lightest
part of the brainstem. It lies just below the diencephalon and is
divided into dorsal (upper) and ventral (lower) areas. Even though
it is a small section of the brain, the midbrain contains many
important nerve cells and fiber tracts running to and from the
cerebral cortex, areas of gray matter, and important reflex
centers. The nerve cells of the midbrain include nuclei of cranial
nerves. One such cranial nerve, the oculomotor nerve,
supplies the eye muscles concerned with movements of the eye in
upward, downward, rotary and inward directions. Another cranial
nerve arising from the midbrain is the trochlear nerve,
which also supplies a muscle that rotates the eye.
中脑
中脑，或叫midbrain（中脑）是脑干最小和最轻的部分。它位于间脑的正下方，并分为背侧（上部）和腹侧（底部）区域。即使它是脑的一小部分，但中脑包含许多往返于大脑皮层、灰质区域，以及重要反射中枢的神经细胞和纤维束。中脑的神经细胞包括颅神经核。这样一个颅神经，眼球运动的神经，为眼睛向上、向下、旋转和向内方向提供了眼睛肌需要的运动。另一个源于中脑的颅神经是滑车神经，它也提供旋转眼睛的肌肉。
CEREBELLUM
The cerebellum, or “little brain,” is located under the back
part of the cerebrum, over the medulla and pons. Like the cerebrum
it has two hemispheres, which are joined together in the middle by
a wormlike structure called the vermis. As a whole, the
cerebellum resembles a butterfly.
小脑
小脑，或叫“little
brain”（小脑）位于大脑后部的下方，在髓质和脑桥的上面。像大脑一样，它有两个半球，中间由一个称为小脑蚓体的蠕虫状结构连在一起。作为一个整体，小脑类似于一只蝴蝶。
Like the cerebrum, the cerebellum has an irregular surface;
but instead of convolutions, it is marked by quite
regular, nearly parallel grooves. Also like the cerebrum, the
cerebellum has a cortex of gray matter on the outside and a center
composed of white matter with several masses of gray matter. These
masses are nuclei; the largest mass is called the dentate
nucleus.
像大脑一样，小脑也有不规则的表面；但不是脑回旋，它具有相当规则的，几乎是平行的凹槽。也像大脑一样，小脑在外部拥有一种灰质皮层和由白质与一些灰质核团组成的中枢。这些核团都是原子核；最大的核团被称为齿状核。
THREE pairs of compact fiber bundles connect the cerebellum
with the rest of the brain and the spinal cord. These fiber bundles
are called cerebellar peduncles. The superior
peduncle is made up mainly of axons of cerebellum nerve cells.
These axons go to and connect with neurons in the midbrain. From
here, some fibers go upward to the thalamus, where they re relayed
to the cerebrum. Other fibers go to the pons, the medulla, and then
to the spinal cord. These fibers carry cerebellar motor impulses to
muscles, especially those of the eyes, neck, and
trunk.
三对紧密的纤维束将小脑与脑、脊髓的其余部分相连接。这些纤维束被称为小脑脚。上脚主要由小脑神经细胞的轴突组成。这些轴突定位并连接中脑的神经元。从这里，一些纤维向上至丘脑，然后至脊髓。这些纤维将小脑的运动脉冲传递给肌肉，尤其是眼睛、颈部和躯干的那些肌肉。
The middle and inferior peduncles consist
mainly of sensory fibers. These fibers carry impulses to the
cerebellum from proprioceptors, sensory receptors in the body that
respond to conditions inside the body. Some proprioceptors are
located in muscles, joints, and tendons, and signal the positions
of these structures in relation to the body as a whole. Another
type of proprioceptor is the vestibular apparatus, which is
located in the semicircular canals of the inner ear and is
concerned with equilibrium. It signals changes in the position of
the head and body and is sensitive to acceleration and
deceleration.
中脚和下脚主要包含感觉纤维。这些纤维将本体感受器的脉冲传递给小脑，身体的感受器对身体外部的头部做出反应。一些本体感受器则位于肌肉、关节和肌腱中，并告知这些结构与身体整体关系位置的那些结构。本体感受器的另一种类型是前庭器官，它位于内耳的半规管中，并与平衡有关。它发出头部和身体位置变化的信号，对加速和减速很敏感。
Functions. The
cerebellum functions as a “motor feedback center,” and is primarily
concerned with the coordination of muscular activity. More
specifically, it is an important mechanism regulating and
graduateing muscle tone for the proper maintenance of posture and
equilibrium and for the smooth performance of voluntary muscular
movements.
功能。小脑的功能是一个“运动反馈中枢”，主要与协调肌肉的活动有关。更具体地说，它是适当的保持姿势与平衡和随意肌肉运动的顺畅表现，调节和改变肌肉张力的重要机制。
Every movement requires the coordinated action (synergy) of
groups of muscles. Those which move a part of the body in one
direction are called agonists; when these muscle contract,
the muscles opposite them, the antagonists, must relax to
permit the motion. Fixating muscles are those that limit the
extent of movement. All THREE muscle groups are involved in
maintaining or changing any movements. Such synergy requires a
complex reciprocal nerve supply of both inhibitory and excitatory
impulses that bring about alterations in muscle tension for any
specific movement to take place. To understand the activity of the
normal cerebellum it is best to consider what happens to a person
in whom the cerebellum is injured or diseased. When such a person
reaches for an object, his hand falls either beyond it or in front
of it (dysmetria). In addition, his movements are jerky and
disjointed (asynergia). Both of these malfunctions combine to bring
about a tremor whenever he reaches out (intention tremor). When he
walks, he must keep his feet wide apart to keep his balance, and as
he walks he sways and staggers and has a tendency to fall backward.
His muscles are weak and flabby and tire easily (muscular
hypotonia). He does not suffer a loss of sensation and there is no
actual paralysis, since the cerebellum does not send motor impulses
to initiate movements as does the motor cortex of the cerebrum.
However, the cerebellum does send impulses to moderate the activity
of the motor cortex and the sensory cortex as well. Thus, the
cerebellum acts to modify the activity of all cerebral cortex
centers.
每个动作都需要肌肉群的协调行动（协同作用）。向一个方向移动身体的那些肌肉被称为主动肌；当这些肌肉收缩时，对面的肌肉拮抗肌，必须松弛以使运动成为可能。固定肌是那些限制运动范围的肌肉。所有三个肌肉群都涉及维持或改变相关的运动。如此的协同作用需要提供一种复杂的抑制脉冲和兴奋脉冲的反向神经，从而改变任何特定运动发生的肌肉张力。要理解正常的小脑活动，最好考虑一下小脑受伤或患病的人会出现什么状况。当这样的人伸手去拿一个物件，他的手不是伸过了，就是还没有到位（测距不准）。另外，他的动作不平稳，而且不连贯（不能协同）。这两种失灵结合起来，每当他伸出手时就会导致颤抖（意向性震颤）。当他行走时，他必须使其两脚分开以保持其平衡，而当他走路时，他会摇晃，而且有向后跌倒的倾向。他的肌肉弱而无力，且易于疲劳（肌张力减退）。他并没有丧失感觉，也没有真的瘫痪，因为小脑没有像大脑的运动皮层那样发出开始动作的运动脉冲。然而，小脑确实会发出脉冲来调节运动皮层以及感觉皮层的活动。因此，小脑修改了所有大脑皮层中枢的活动。
PONS
The pons lies below the cerebellum and the cavity of the
fourth ventricle, just above the medulla. It is a bulging mass of
fibers connecting to the cerebellum above and the medulla below. It
resembles a horseshoe, the open ends of which join with the middle
peduncles of the cerebellum. The pons also contains the nuclei of
several cranial nerves. Because of its many fiber tracts and
important nuclei, injury to the pons may result in deep coma, lack
of muscle tone, and a loss of all reflexes.
脑桥
脑桥位于小脑和第四脑室空腔的下方，髓质的正上方。它是一个鼓起的，上面连接小脑，下面连接髓质的纤维团。它类似于马蹄铁，其开口末端与小脑的中脚相连。脑桥也包含一些颅神经的原子核。因为它有许多纤维束和重要的原子核，因此损伤脑桥可能导致深度昏迷，缺乏肌肉张力以及失去所有的条件反射。
MEDULLA
The medulla extends from the lower border of the pons and
joins with the spinal cord at the foramen magnum (the large
opening at the back of the base of the skull). As in the spinal
cord, its white matter is on the outside and its gray matter is on
the inside.
髓质
髓质从脑桥下缘伸出，并与枕骨大孔（头骨底部后面的大开口）的脊髓相连。像脊髓一样，其白质在外面，而髓质的灰质是在里面。
The medulla transmits ascending and descending fiber tracts
to and from the spinal cord, and it is in the medulla that most of
the pyramidal motor tracts cross one another. The medulla also
contains many important nuclei, several of which give rise to
cranial nerves. One nucleus, the nucleus ambiguous, sends
axons through THREE of the cranial nerves to supply the muscles of
the larynx, pharynx, and side of the neck.
髓质传递上升和下降纤维束往返于脊髓，在髓质中，大多数锥状的运动束相互交叉。髓质还包含许多重要的原子核，其中一些会产生颅神经。一个原子核，疑核，通过三条颅神经传送轴突，以满足喉、咽，以及颈一侧肌肉的需要。
Centers that control breathing are also found in the medulla.
Apparently, there is both an inspiratory and an expiratory center,
which are thought to be reciprocally connected. When these centers
are damaged, as occurs in bulbar poliomyelitis, there may be a
complete, and sometimes permanent, cessation of
breathing.
在髓质中也发现了控制呼吸的那些中枢。很明显，存在一个吸气中枢和呼气中枢，人们认为它们是相互连接的。当这些中枢受到损害时，就如同延髓脊髓灰质炎一样，可能有一个完全的，有时是永久性的呼吸中断。
The medulla also contains centers that control the rate of
heartbeat and the degree to which the blood vessels must be
constricted to maintain a normal blood pressure.
髓质也包含控制心跳频率，以及血管必须收缩来维护正常血压程度的中枢。
RETICULAR FORMATION
Extending throughout much of the brain, from the brainstem to
the cerebral cortex, is a special network of nerve fibers and
nuclear masses known as the reticular formation (or
reticular activating system). Most of the reticular formation is
found in the midbrain, pons, and medulla, although branches extend
upward as far as the cerebral cortex.
网状结构
贯穿脑的许多区域，从脑干到大脑皮层，是一种特殊的神经纤维网络，以及被称为网状结构（或网状激活系统）的核子团。在中脑、脑桥和髓质中，发现了大部分的网状结构，尽管这些分支向上延伸至大脑皮层。
The reticular formation serves to control the overall
electrical activity of the central nervous system. Motor impulses
from the cerebellum and brainstem are augmented as they pass
through the reticular formation to the spinal cord. However, this
activity of the reticular formation is largely controlled by the
cerebral cortex, so that if an animal’s cerebrum is removed and the
reticular formation is no longer controlled by the cerebral cortex,
all of the animal’s muscles will become stiff, a condition known as
decerebrate rigidity.
网状结构用于控制中枢神经系统的全部电活动。来自小脑和脑干的运动脉冲在它们穿过网状结构到达脊髓时得到了增强。然而，网状结构的这种活动在很大程度上是受大脑皮层控制的，所以，如果切除了动物的大脑，并且网状结构不再受大脑皮层的控制，那么动物的所有肌肉都会变硬，
一种被称为去大脑僵直的状况。
Just as the cerebral cortex controls the reticular formation,
the reticular formation is capable of influencing the electrical
activity of the cerebral cortex. As a result, the reticular
formation plays a major role in maintaining a state of sleep or
wakefulness. By filtering out many sensory impulses that would
normally reach the cerebral cortex, the reticular formation
encourages sleep. By allowing more signals to reach the cortex, it
serves to arouse a person from sleep. The reticular formation also
plays an important role in maintaining a person’s state of
alertness once he is awake.
正像大脑皮层控制网状结构一样，网状结构也能影响大脑皮层的电活动。结果是，网状结构在维持睡眠或清醒状态中起着重要作用。通过过滤掉许多会正常到达大脑皮层的感官脉冲，网络结构会有助于睡眠。网络结构在人醒来时保持清醒的状态中也起着重要作用。
CRANIAL NERVES
Nerves that originate in the brain are called cranial
nerves. These nerves, of which here are 12 pairs, have many
diverse actions, which are often indicated by their names. In
addition to these names, cranial nerves are designated by numbers
corresponding to order in which they arise from the
brain.
颅神经
源自脑的神经被称为颅神经。这些神经有12对，有许多不同的活动，通常用它们的名称来表示。除了这些名称外，颅神经也由它们从脑中产生的对应顺序数字来指定。
Some cranial nerves are entirely sensory. These are the
olfactory (I), optic (II), and auditory (VII) nerves. Other cranial
nerves are entirely motor. The oculomotor (III),
trochlear (IV), and abducens (VI) nerves stimulate
movements in the muscles that move the eyeball, while the
accessory (XI) and hypoglossal (XII) nerves supply
the muscles of the neck and larynx, and the muscles of the tongue,
respectively.
某种颅神经完全是感觉神经。它们是味觉神经（I），视觉神经（II）和听觉神经（III）。其它的颅神经完全是运动神经。眼球运动神经（III），滑车神经（IV）和外展神经（VI）刺激眼球移动的肌肉运动，而附属神经（XI）和舌下神经（XII）分别为颈部和喉部，以及舌头的肌肉提供需要。
Some cranial nerves are both sensory and motor. The
trigeminal (V) carries sensory impulses from parts of the face,
eyes, nose, teeth, gums, and tongue, and carries motor impulses to
the jaw muscles used in chewing. The facial (VII) nerve has sensory
fibers from the front two THIRDS of the tongue and motor fibers
leading to muscles of the face, scalp, outer ear, and neck. It also
has motor fibers that stimulate the secretion of saliva from two of
the salivary glands. The glossopharyngeal (IX) nerve carries taste
sensations from the back THIRD of the tongue and sensations of
touch and temperature from the palate, tonsils, and pharynx. Some
of its motor fibers lead to one of the muscles of the pharynx,
while others stimulate saliva secretion in the parotid salivary
gland.
有些颅神经既是感觉神经也是运动神经。三叉神经（V）传递来自脸、眼、鼻、牙、牙龈和舌头部位的感觉脉冲，也将运动脉冲传递至用于咀嚼的颚肌。面部（VII）神经有源自舌头前三分之二的感觉神经和通向面部、头皮、外耳和颈部肌肉的运动纤维。它还有来自两个唾液腺刺激唾液分泌的运动纤维。舌咽神经（IX）从舌头的后三分之一传递味觉感，以及从上颚、扁桃体和咽喉传递触觉和温度的感觉。它的一些运动纤维通向咽喉的一块肌肉，而其它的刺激腮腺分泌唾液。
The vagus (X) nerve has the widest distribution of any
of the cranial nerves. It contributes motor impulses to muscles in
the larynx and pharynx, and also leads to the heart where its
impulses slow the rate of heartbeat. The vagus also controls
involuntary muscles in the bronchi, esophagus, stomach, pancreas,
gall bladder, small intestine, and the first THRID of the colon. It
also stimulates the secretion of stomach and pancreatic juices. The
sensory function of the vagus nerve is quite limited. It supplies
sensation to a tiny area around the opening of the external
ear.
迷走神经（X）在任何颅神经中都分布最广。它为喉和咽部的肌肉提供运动脉冲，还通向心脏，在那里它的脉冲降低了心率。迷走神经还控制支气管、食道、胃、胰腺、胆囊、小肠和三分之一结肠的不随意肌。它还刺激胃液和胰液分泌。迷走神经的感觉功能相当有限。它为外耳开口周围的极小区域提供感觉。
