CHAPTER 10 NERVOUS SYSTEM central nervous system (CNS) peripheral nervous system (PNS) The...

CHAPTER 10

NERVOUS SYSTEM

• central nervous system (CNS)

• peripheral nervous system (PNS)

The composition of nervous system:

(include the brain and the spinal cord )

(composed of the neurons and neuroglia cells)

Somatic nervous system

Visceral nervous system

中枢神经系统中枢神经系统

周围神经系统周围神经系统

脑、脊髓脑、脊髓

躯体躯体

内脏内脏

脑脑

脊髓脊髓

内脏内脏躯体躯体

1. Structure and Function of the Neurons

2. Sensory Function of NS

3. Control of body movement

4. Autonomic NS

5. Higher Functions of NS

All contents of chapter 10:

1. Structure and Function of the Neurons神经元神经元

感觉感觉

运动运动

自主自主 NSNS

高级功能高级功能

Structure and maintenance of Neurons

SECTION A

Neurons

• Basic Structure

• cell body (soma) 胞体

• dendrites 树突

• axons (nerve fiber) 轴突

轴丘

朗飞结

Functional Classes Of Neurons

神经元的分类　

Three functional classes of neurons:

1. Afferent neurons: receptor CNS

2. Efferent neurons: CNS effector cells

3. Interneurons: connect afferent and efferent neurons

传入神经元

传出神经元

中间神经元

传入 传出 中间

Nerve fibers have myelin sheaths are called myelinated nerve fiber

• myelinated nerve fiber

• unmyelinated nerve fiber.

Nerve fibers lack myelin sheaths are called unmyelinated nerve fiber

有髓神经纤维

无髓神经纤维

有髓鞘

无髓鞘

Nerve Fiber

Classification of nerve fibers 分类

1. Electrophysiologic properties 电生理学的特性

divides fibers into three groups :

A , A , A ,AType A:

Type B: myelinated.

Type C: unmyelinated.

Table 10-1 Classification of fiber types

Fiber Type Function Fiber Diameter(m)

Conduction Velocity(m/s)

SpikeDuration(ms)

Absolute RefractoryPeriod(ms)

A A Proprioception; Somatic motor

1322 70120 0.40.5 0.41.0

A Touch, Pressure 813 3070

A Motor to muscle spindles 48 1530

A Pain, Temperature, Touch 14 1230

B Preganglionic autonomic 13 315 1.2 1.2

C sC Postganglionic sympathetics 0.31.3 0.72.3 2.0 2.0

drC Pain, Reflex responses 0.41.2 0.62.0

传导速度

Fiber type

Origin Diameter(m)

Conduction Velocity(m/s)

Electro-Physiologictypes

Ⅰ a b

Muscle spindle, annulospiral endingGolgi tendon organ

1222

About 12

70120

about 70

A

A

Ⅱ Muscle spindle, flower-spray ending,Touch receptors

512 2570 A

Ⅲ Pain and temperature receptors, some touch receptors

25 1025 A

Ⅳ Pain and other receptors 0.11.3 1 C

纤维的直径及来源 2. based on origin and diameter of fibers

来源直径

• Conduction Velocity of nerve fiber

1. fiber diameter:

depends on:

2. whether or not the fiber is myelinated:

3. temperature:

The larger has the axon diameter, higher the conduction velocity

myelinated fibers is fasterthan unmyelinated fibers.

(saltatory conduction)

Lower was the temperature, the slower the conduction velocity.

传导速度

直径大传导快

有髓比无髓快

温度低则慢

•characteristics of nerve fibers conduction: 传导特征

(1) Integrity

(2) Isolated propagation

(3) bidirectional propagation

(4) Indefatigability

生理完整性

绝缘性

相对不疲劳性

双向性

Axonplasmic Transport 轴浆运输

cell body

• Anterograde 顺向轴浆运输

• retrograde 逆向轴浆运输

快（ 40-500 mm/d ），慢（ 1-12 ）

nerve terminal

cell body nerve terminal

Axonplasmic transport

Tetanus toxin, herpes

Linking proteins, microtubules

Glial (Neuroglia ) Cell

• The classification of Neuroglia Cell

1. oligodendrocytes

2. Astrocytes

3. microglia

4. Schwann cells

星形 ~

少突 ~

小 ~

施万C

• The functions of neuroglia cells:

(1)Supportability 支持

(2) plerosis and regeneration 修复与再生

(3) Substantial metabolism and nutritive function

(4) isolated and Barrier 绝缘屏障

(5) Maintain the suitable ionic concentration

(6) intape and excrete neurotransmitter 神经递质

代谢营养

离子浓度

SECTION B

Synapse突触

•Two kinds of synapse by mechanism:

2. chemical synapses: 化学突触

1. electrical synapses

use chemical transmitter(s)

electrical mechanism.

电突触

Chemical Synapses

1. Typical Chemical Synapse

2. Non-synaptic chemical transmission

经典突触

非突触性化学传递

Synapse:

Synapse is the anatomically specialized junction between

two neurons, where information is transmitted from one

neuron to another.

一个神经元的轴突末梢与其他神经元的胞体或突起相接触并进行信息传递的部位。

Typical Chemical Synapse

• includes three components:

1. pre-synaptic membranes

2. post-synaptic membranes

3. synaptic cleft.

• Structure of Synapse :

突触前膜

突触间隙

突触后膜

membrane

Structure of Synapse :

A. axon-somatic synapses

B. axo-axonal

synapses

C. axo-dendritic synapses

• Classification of synapses

1. based on the contacting position of the synapses

轴 - 体

轴 - 树

轴 - 轴

分类

• Classification of synapses

2. based on the functions:

A. Excitatory synapses

B. Inhibitory synapses

兴奋性

抑制性

Mechanism of synaptic transmission

(Electric-chemical-electric transmission processes)

电—化学 --- 电

过程：

（ 1 ）突触前膜去极化；

（ 2 ） Ca2 ＋进入突触小体；

（ 3 ）递质释放；

（ 4 ）递质与受体结合；

（ 5 ）产生突触后电位（ PSP ）

ion

ion

Electric-chemical-electric transmission processes:

presynaptic processes

AP propagate to synaptic knob Ca2+ influx

Vesicle move to presynaptic membrane

Release neurotransmitters

synaptic cleft: transmitter diffused to the postsynaptic membrane

postsynaptic membrane

transmitter binding to the receptors

cause the Postsynaptic Potential （ PSP ）

递质

What will happen in neurotransmitters ?

1. decompose: by enzymes

2. reuptake: be transported back into the synaptic knob

(Acetylcholine cholinesterase )

( epinephrine and norepinephrine )

AChEACh

3. Go to peripheral interstitial space

递质

分解

重利用

外周组织

Electric-chemical-electric transmission processes:

presynaptic processes

AP propagate to synaptic knob Ca2+ influx

Vesicle move to presynaptic membrane

Release neurotransmitters

synaptic cleft: transmitter diffused to the postsynaptic membrane

postsynaptic membrane

transmitter binding to the receptors

cause the Postsynaptic Potential

递质

（ PSP ）

Postsynaptic Potential

1. Excitatory Postsynaptic Potential (EPSP)

2. Inhibitory Postsynaptic Potential (IPSP)

兴奋性突触后电位

抑制性突触后电位

(1) Excitatory postsynaptic potential (EPSP)

Concept:

The excitatory transmitter cause the

Depolarization of postsynaptic membrane.

兴奋性递质引起的突触后膜去极化。

• The mechanism of EPSP

Action potential Presynaptic membrane released excitatory transmitters

excitatory transmitters diffuse to postsynaptic membrane in synaptic cleft

chemically gated channels open, Na+ influx (main) and K+ efflux

postsynaptic membrane is depolarized

EPSP

bind to receptor

(Local potential)

轴突冲动 → 突触前膜释放兴奋性递质

→ 经突触间隙扩散并与突触后膜受体结合

→ 突触后膜提高对 Na+ 、 K+ ，尤其对 Na+

的通透性→突触后膜去极化

（ 2 ） Inhibitory postsynaptic potential (IPSP)

The inhibitory transmitter cause the

hyperpolarization of postsynaptic membrane.

Concept:

抑制性递质引起的突触后膜超极化。

Inhibitory nerve

terminal excite

• The mechanism of IPSP

Presynaptic membrane released inhibitatory transmitters

inhibitatory transmitters diffuse to postsynaptic membrane in synaptic cleft

bind to receptor

chemically gated channels open,Cl- influx (main) and K+ efflux

postsynaptic membrane is hyperpolarized

IPSP

(graded potential)

抑制性 N 元末梢兴奋 → 释放抑制性递质 →

经扩散与突触后膜的受体结合 → 提高突触

后膜对 Cl- 的通透性 → 突触后膜超极化

Action potential develop on the postsynaptic neurons

The summation of EPSP

depolarized to threshold potential

generated the action potential

突触后电位的总和

总和

去极达阈电位

动作电位

Characteristics of synaptic transmission

(1) One Way Conduction

(2) Synaptic Delay

from the presynaptic to the postsynaptic neuron

The delay is due to the time it takes for the release of neurotransmitter and its action on the postsynaptic membrane.

单向传布

突触延搁

(3) Integration (Summation )

• more than one synaptic knob activate at the same time spatial summation

• repeated afferent stimulus temporal summation

Characteristics of synaptic transmission

时间总和

总和

空间总和

(4) susceptibility

Internal Environment change

affect the release of transmitters or transmitter

bind to receptors

（ hypoxia, acid poisoning, some drug )

(5) Fatigue Stimulate a synapses continuous

the number of discharges

( due to exhaustion of transmitters.)

对内环境变化的敏感性

缺氧 、酸中毒等

易疲劳性

递质耗竭

(6)Synaptic plasticity

突触传递的功能可发生较长时间的增强或减弱，与脑的高级功能密切相关。

突触传递的可塑性

Characteristics of synaptic transmission

2. Non-synaptic chemical transmission非突触性化学传递

Varicosity ：

release transmitter

bind to the nearly receptor

of the effector cells

曲张体

效应细胞 R

非突触性化学传递与经典突触传递的区别：

1. 没有经典突触的一对一关系

2. 是否成为靶细胞以及是否出现效应，

取决于递质扩散范围内神经元上的受体。

Electrical synapse

• Basic structure: gap junctions

• Characteristics:

bidirectional transmission

• Function:

cause the synchronization of

discharge of different neurons

bidirectional propagation

缝隙连接

双向性

传递信息并促进不同神经元同步性放电

the propagation of AP in an unmyelinated nerve fiber

Saltatory conduction

the propagation of AP in an myelinated nerve fiber

Mechanism: Local Current

局部电流 跳跃式传导

A nerve trunk

impulse

nerve-fibers

smell

pain