Transcript Chapter 11-自律神經及體運動神經系統檔案

Chapter 11
The nervous system:
autonomic and motor
systems
1. The autonomic nervous systems
自律神經系統
2. The somatic nervous system
體神經系統
I. The Autonomic Nervous System
 The autonomic nervous system (ANS) innervates all
effector organs and tissues in the body except the
skeletal muscles, including cardiac muscles, smooth
muscles, glands, and adipose tissue
除了骨骼肌外，自律神經系統幾乎支配了所有的器官及
組織，包括心肌、平滑肌、腺體及脂肪組織等
 It is called ‘autonomic’ because its functions occur at a
subconscious level  also referred to as the
involuntary nervous system
它之所以稱為「自律的」，是因他的功能是在下意識或
無意識下產生的，因此也稱為不隨意神經系統
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Dual Innervation of the Autonomic
Nervous System
 Primary function—regulate organs to maintain homeostasis
主要功能在調控器官維持在一恆定狀態
 Parasympathetic and sympathetic activities tend to oppose
each other 副交感神經及交感神經的活性常常是彼此相反的
– Parasympathetic nervous system—rest 休息
– Sympathetic nervous system—fight or flight response
戰鬥或逃跑反應
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
In this detailed schematic
diagram of the ANS,
parasympathetic
pathways 副交感神經路徑
are shown in purple, and
sympathetic pathways
交感神經路徑 in green

Both branches of the ANS
generally innervate the
same organs 自律神經系
統分支通常支配相同的器官

Only one side of the body
is shown for each system;
thus there are actually two
sympathetic chains, two of
each cranial nerve, and so
on 此圖只秀出其中一邊，
事實上有兩條交感神經鏈
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Figure 11.1 Dual innervation in the
autonomic nervous system.
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Anatomy of Autonomic Pathways
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Education, Inc., publishing
as Benjamin Cummings.
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
In autonomic nervous system consists of efferent pathways containing two neurons
arranged in series that communicate between the CNS and the effector organ
自律神經系統由兩條傳出神經路徑以連續排列方式所組成，可溝通中樞與作用器官

The neurons communicate with each other through synapses located in peripheral
structures called autonomic ganglia 突觸末梢與神經元互相溝通的結構稱為自律神經節

The preganglionic neuron originates in the CNS and travels to a ganglion in the periphery,
where it synapses with a postganglionic neuron that innervates one of several types of
effector organ 節前神經的神經元位於中樞，神經纖維中止於末梢的神經節；在神經節，節
前神經纖維與節後纖維形成突觸，節後纖維的軸突末梢則支配許多不同的器官

A single preganglionic neuron generally synapses with several postsynaptic neurons; in
addition, other neurons located entirely within each other ganglion, called intrinsic neurons
通常一條節前神經的軸突末梢會與許多節後神經形成突觸；此外會有一些神經完全位於神經
節內，稱為內生性神經
Anatomy of the Sympathetic Nervous System
 Preganglionic neurons in the sympathetic nervous
system originate in thoracolumbar spinal cord  the
sympathetic nervous system is sometimes called
thoracolumbar system
交感神經的節前神經起源於脊髓的胸腰椎系統，因此
交感神經系統有時也稱為胸腰椎系統
 General anatomy 一般的解剖構造
–
Short preganglionic neurons to sympathetic chain
節前神經較短
–
Long postganglionic neurons from chain to effector organs
節後神經較長
–
Ganglia linked together in sympathetic chain
神經節連結在一起形成交感神經鏈
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Anatomy of the Sympathetic Nervous System
交感神經鏈
外側角
節後神經元
作用者器官
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Education, Inc., publishing as
Benjamin Cummings.
嗜鉻性細胞
腎上腺髓質
脊髓的胸椎
旁系的(附屬的)神經節
及腰椎
Figure 11.3 Anatomical pathways of preganglionic and postgenglionic
neurons in the sympathetic nervous system.

Most sympathetic preganglionic neurons synapse with postganglionic neurons in ganglion
in the sympathetic chain (1)
大部分交感神經的節前神經都在交感神經鏈的神經節內與節後神經形成突觸

Some sympathetic preganglionic neurons innervate secretory cells of the adrenal medulla
(2) 有些交感神經的節前神經則是在腎上腺髓質內支配分泌性細胞

Still other sympathetic preganglionic neurons synapse in collateral ganglia that are
independent of the sympathetic chain (3)
也有一些交感神經的節前神經在一些與交感神經鏈不相關的附屬神經節形成突觸
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Anatomy of the Sympathetic Nervous System
背根
腹根
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Benjamin Cummings.
Figure 11.4 The most common pathway of sympathetic fibers.
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
The sympathetic preganglionic neurons exits the spinal cord as part of the ventral
root and travels to the spinal nerve

Shortly after entering the spinal nerve the preganglionic neuron exits the nerve and
travels via a white ramus 白枝 to a ganglion in the sympathetic chain, where the
neuron synapses with a postganglionic neuron

The postganglionic neuron then returns to the spinal nerve via a gray ramus 灰枝
Anatomy of the Sympathetic Nervous System
Figure 11.5 Sympathetic innervation of the adrenal gland.
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
The various sympathetic ganglia are linked together to form sympathetic chains (1)

A very important exception to the arrangement is a group of long preganglionic
neurons that innervate endocrine tissue--the adrenal medulla--instead of synapsing
on postganglionic neurons (2)

The adrenal glands, located within fat pads on top of each kidney, consist of an outer
cortex and inner medulla

Sympathetic preganglionic neurons innervate chromaffin cells of the adrenal medulla,
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stimulating
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the release of epinephrine (and a small amount of norepinephrine) into
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blood
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Anatomy of the Parasympathetic Nervous
System
 Preganglionic neurons of the parasympathetic nervous
system originate in brainstem or sacral spinal cord  is
sometimes called craniosacral system 顱薦椎系統
 Anatomy
–
Long preganglionic neurons to ganglia near effector organ
–
Preganglionic neuron communicates with postganglionic
neuron in ganglia
–
Short postganglionic neurons from ganglia to effector organs
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Anatomy of the Parasympathetic Nervous System
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Pearson
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publishing as
Benjamin
Cummings.
Figure 11.6 Parasympathetic nervous system pathways.

Parasympathetic preganglionic neurons originate in either the brainstem or the sacral
spinal cord, and their axons are found in cranial and pelvic nerves, respectively

These axons from synapses with postganglionic neurons in ganglia close to or within
the effector organs

One important cranial nerves is the vagus nerve (cranial nerve X), which originates
in the medulla oblongata and innervates much of the viscera, including the lung,
heart, stomach, small intestines, and liver
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Anatomy of the Parasympathetic Nervous
System
• Cranial Nerves 腦神經
– Cranial nerve X = vagus nerve 迷走神經
– Cranial nerve III = oculomotor 動眼神經
– Cranial nerve VII = facial nerve 顏面神經
– Cranial nerve IX = glossopharyngeal nerve 舌咽神經
• Spinal Nerves 脊神經
– Pelvic nerves distinct from somatic spinal nerves
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The Mixed Composition of Autonomic Nerves
• Efferent fibers
– Autonomic nervous system
• Afferent fibers
– Transmit information from visceral receptors to CNS
– Important in maintaining homeostasis
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Autonomic Neurotransmitters and
Receptors
 The two neurotransmitters in the PNS are acetylcholine and
norepinephrine
 Neurons that release the acetylcholine are referred to to as
cholinergic
— All the preganglionic neurons of sympathetic and parasympathetic
nerves & postganglionic neurons of parasympathetic nerves are
cholinergic
— The somatic neuron of the efferent nervous system is also cholinergic
 Neurons that release the norepinephrine are referred to to as
adrenergic
— Almost all sympathetic postganglionic neurons are adrenergic
— Some sympathetic postganglionic neurons release acetylcholine,
specifically those innervate the sweat glands
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Autonomic Neurotransmitters and Receptors
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Figure 11.7 Neurotransmitters and receptors in the autonomic nervous system.
(a) Neurotransmitters and receptors for the three distinct anatomical pathways of the
sympathetic nervous system. In all cases, the preganglionic neuron releases
acetylcholine (Ach), which then binds to nicotinic cholinergic receptors on either
postganglionic neurons or endocrine cells in the adrenal medulla. The postganglionic
neurons release (NE), which binds to adrenergic receptors on the effector organs.
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Autonomic Neurotransmitters and
Receptors
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Figure 11.7 Neurotransmitters and receptors in the autonomic nervous system.
(b) Neurotransmitters and receptors in the parasympathetic pathway. Acetylcholine is
released from both preganglionic and postganglionic neurons; it binds to nicotinic
cholinergic receptors on the postganglionic neuron, and to muscarinic cholinergic
receptors at the effector organ.
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Types of Cholinergic Receptors
 Nicotinic 尼古丁的 cholinergic receptors are located on the cell bodies
and dendrites of sympathetic and parasympathetic postganglionic
neurons, on chromaffin cells of the adrenal medulla, and on skeletal
muscle cells
–
Open channels for cations (Na+ and K+)
–
Result = depolarization
 Muscarinic 蕈毒鹼的 cholinergic receptors are found on effector
organs of the parasympathetic nervous system, such as the heart,
smooth muscles controlling the contraction of the eye or the digestive
tract
–
G protein coupled
–
Effect depends on target cell
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Types of Adrenergic Receptors
 There are two major classes of adrenergic receptors located in effector
organs of the sympathetic nervous system: alpha () and beta ()
 Each of these is further divided into sub-classes: 1 and 2, and 1, 2,
and 3
 Adrenergic receptors are coupled to G proteins that either activate or
inhibit second messenger systems
 The  receptors have a greater affinity for norepinephrine than
epinephrine and are generally excitatory
 1 and 3 receptors have approximately equal affinities for
norepinephrine and epinephrine, and tend to be excitatory
 2 receptors have a much greater affinity for epinephrine than
norepinephrine, and are generally inhibitory
P309-310
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Figure 11.7 Signal transduction mechanism at
effector organs of the sympathetic nervous system
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 Binding of norepinephrine or epinephrine to an 1 adrenergic receptor
triggers activation of the phosphatidylinositol second messenger system
 Alpha 1 adrenergic receptors are most located in vascular smooth
muscle  1 agonist can be used to treat congestion 充血
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Benjamin Cummings.
Figure 11.7 Signal transduction mechanism at
effector organs of the sympathetic nervous system
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 Binding of norepinephrine or epinephrine to an 2 adrenergic receptor
triggers inhibition of the cAMP second messenger system, whereas
binding to a  adrenergic receptor triggers excitation of the cAMP
second messenger system
Summary of Adrenergic Receptors
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Autonomic Neuroeffector Junctions
 The synapse between an
efferent neuron and its effector
organ is called a neuroeffector
junction 神經-作用者聯合
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 Near the effector organ the
axon of a postganglionic
neuron splits into branches
bearing swellings called
varicosities 囊節
 Whereas voltage-gated Na+
and K+ channels are present
thought the axon to support
propagation of action
potentials, voltage-gated Ca2+
channels are concentrated at
the varicosity
 Neurotransmitter is stored in
synaptic vesicles 突觸小泡 in
the varicosity
Figure 11.9 Neuroeffector junctions of the
autonomic nervous system.
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Autonomic Neuroeffector Junctions
 When an action potential
depolarizes a varicosity, voltagegated Ca2+ channels open,
allowing Ca2+ to enter the cell and
triggering the release of
acetylcholine by exocytosis 胞吐
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 Acetylcholine binds to
muscarinic receptors on the
effector organ membrane, thereby
activating a G protein
 Once acetylcholine is degraded
by acetylcholinesterase located
on the effector organ, choline is
actively transported back into the
postganglionic varicosity and
used to synthesize more
acetylcholine
Figure 11.10 Neurotransmitter release
from varicosities.
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Autonomic Neuroeffector Junctions
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 When an action potential
depolarizes a varicosity,
voltage-gated Ca2+ channels
open, allowing Ca2+ to enter the
cell and triggering the release
of norepinephrine by exocytosis
 Norepinephrine binds to
adrenergic receptors on the
effector organ membrane,
thereby activating a G protein
 Some norepinephrine is
actively transported back into
the postganglionic neuron’s
varicosity, where it is degraded
by monoamine oxidase
(MAO) in mitochondria
Figure 11.10 Neurotransmitter release
from varicosities.
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Regulation of Autonomic Function
 Dual innervation of organs
 Balance between parasympathetic and sympathetic activity
–
Parasympathetic—rest, quiet, relaxed states, increase gastrointestinal
activities; decrease heart rate and blood pressure
–
Sympathetic—excitation; fight-or-flight response; prepare for
emergency/stress/exercise; increase heart rate and blood pressure;
mobilize energy stores; pupillary dilation; decrease
gastrointestinal/urinary functions
 Most changes in the activity of the ANS are accomplished through the
operation of visceral reflexes
 Increases in parasympathetic activity coupled with decreases in
sympathetic activity
 Increases in sympathetic activity coupled with decreases in
parasympathetic activity
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Figure 11.11 Autonomic reflex
response that controls blood
pressure when a person stands up.
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Regulation of Autonomic Function
 Hypothalamus下視丘, pons
橋腦, medulla 延腦 
Maintenance of homeostasis
 Cerebral cortex 大腦皮質,
limbic system邊緣系統 
Emotions
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Figure 11.12 Area of the brain that
regulate autonomic function. This
midsagittal section of the brain reveals the
pons 橋腦 and medulla oblongata 延腦 of the
brainstem 腦幹 and the hypothalamus 下視丘
, all of which regulate autonomic function.
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II. Somatic Nervous System
 The somatic nervous system 體神經系統 controls
only one type of effector organ—skeletal muscle
骨骼肌, which are connected to bones and thus
function in support and movement of the body
 The somatic nervous system has only a single
type of efferent neuron: motor neurons 運動神經
 Most skeletal muscle is under voluntary control
 the somatic nervous system is also referred to
as the voluntary nervous system 隨意神經系統
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Anatomy of the Somatic Nervous System
Figure 11.13 Anatomy of
somatic nervous system
pathway. The somatic nervous
system consists of motor
neurons, which originate in the
ventral horns of the spinal cord
and terminate on skeletal
muscle fibers throughout the
body.
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 In the somatic nervous system, a single motor neurons travels from
the central nervous system to a skeletal muscle cell 骨骼肌細胞
 Motor neurons originate in the ventral horn 腹根 of the spinal cord
脊髓 and receive input from multiple sources, including afferents (for
spinal reflexes), the brainstem 腦幹 extrapyramidal tracts 錐體外路徑,
and the cerebral cortex 大腦皮質 pyramidal tract 錐體路徑
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Anatomy of the Somatic Nervous System
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 A single motor neuron innervates
many muscle cells (called muscle
fibers), but each muscle fiber is
innervated by only one motor
neuron
 A motor neuron plus all the
muscle fibers it innervates is
called a motor unit 運動單位
 When a motor neuron is
activated, it stimulates all the
muscle fibers in its unit to
contract 收縮
 Note that the muscle fibers within
a given motor unit are scattered
分散 throughout the muscle
Figure 11.14 Motor units.
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Neuromuscular Junction
Synapse between a motor neuron and a muscle fiber
 Each branch of a motor neuron
synapses with a skeletal muscle fiber
at a single highly specialized central
region of the fiber called the
neuromuscular junction 神經肌肉聯合
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 The axon terminals of the motor
neuron, called terminal boutons 終末
膨大, store and release
acetylcholine, the only
neurotransmitter in the somatic
nervous system
 Opposite these terminal boutons is a
specialized region of the muscle
fiber’s plasma membrane called the
motor end plate 運動終板, which has
containing large numbers of nicotinic
Figure 11.15 Functional anatomy
of the neuromuscular junction.
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Neuromuscular Junction

When an action potential arrives at the axon terminal of a motor neuron (), voltagegated calcium channels open and Ca2+ enters the cytosol ()  triggers the release
by exocytosis of acetylcholine ()

Acetylcholine diffuses to and binds to nicotinic receptors at the motor end plate,
opening cation channels  Na+ enters the cell (), producing and end -plate
potential (EPP) that generates currents throughout the plasma membrane of the
skeletal muscle cell (), depolarizing the membrane to threshold to generate an
action potential ()

The action potential spreads
along the skeletal muscle cell
membrane, ultimately
stimulating contraction

Acetylcholinesterase degrades
acetylcholine to produce
acetate and choline () 
choline is actively transported
into the terminal bouton (),
where it can be used to
synthesize more acetylcholine
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Figure 11.15 Functional anatomy
of the neuromuscular junction.
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Myasthenia Gravis
 Myasthenia gravis 重症肌無力 is a disease affecting transmission at
neuromuscular junction
 Because the muscles most frequently affected are those of the head,
difficulties in speaking (dysarthria) 發音困難 and in swallowing
(dysphagia) 吞嚥困難 are common symptoms; dropping of the eyelids
(ptosis) 眼瞼下垂 is also a common sign
 We now know that myasthenia gravis is an autoimmune disease
自體免疫疾病— a disease in which the immune system 免疫系統 attacks
proteins that are normal components of body tissues
 In myasthenia gravis, the immune system produces antibodies 抗體
against acetylcholine receptors at the neuromuscular junctions 
decrease in the number of functional receptors on the cell surface
impairs the ability of these muscle cell to respond to acetylcholine
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Curare
 Curare 劍毒 is an extract of a plant (Chondrodendron tomentosum)
found in South America
 When an animal was struck by a curare-laced arrow or dart, it would
become paralyzed and eventually die from respiratory failure 呼吸衰竭
 The effective component of curare is a compound called tubocurarine,
which blocks communication at the neuromuscular junction 
tubocurarine binds to nicotinic receptors, thereby preventing
acetylcholine from binding (antagonism 拮抗作用)
 When this occurs, skeletal muscles are unable to contract even when
action potentials are transmitted by the motor neurons that innervate
them
 Curare was first used as a skeletal muscle relaxant 骨骼肌鬆弛劑 to
supplement general anesthesia 全身麻醉劑 in the 1930s
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