适用课程: 人体解剖学(0232000810),人体解剖学(0232000910),人体解剖学(0232001010),人体解剖学(双语)(0232001011),人体解剖学(双语)(0232001111),人体解剖学(0232005610),人体解剖学(23058001),人体解剖学(23058004)【访问量:1461991】
SYSTEMATIC ANATOMY

part  nervous system

 Introduction

Chapter 1  General Description

. Composition of Nervous System

Reflex and reflex archs

Terminology

Chapter 2  Central Nervous System

Section 1  Spinal Cord

. External Features of Spinal Cord

. Internal Structure of Spinal Cord

Section 2   Brain Stem

I.  External Features

II.  Internal Structure 

III.  Transverse Sections of Brain Stem

IV  1esions of Brain Stem

Section 3  Cerebellum

I.  Lobes of Cerebellum

II.  Cerebellar Cortex

III.  Central Nuclei of Cerebellum

IV.  Cerebellar Cortex and Cerebellar Peduncles

V. Functions

Section4.  Diencephalon

I .  Dorsal Thalamus

II .  Epithalamus

III.  Subthalamus

IV.  Metathalamus

V.  Hypothalamus

VI. Third Ventricle

Section 5.  Telencephalon

I .  External Features

II .  Limbic System

III.  Cerebral Cortex

IV.  Internal Structures

Chapter 3  Nervous Pathways

Section 1.. Sensory (Ascending)Pathways

.Superficial Sensory Pathways

.Deep Sensory (or the proprioceptive) Pathways

. Visual Pathways

. Auditory Pathway

. Equilibratory Pathway

Section 2.. Motor (Descending)Pathways

. Pyramidal System

. Extrapyramidal System

Chapter 4   Meninges and Blood Vessels of Brain and Spinal Cord, and the Cerebrospinal Fluid

Section 1... Meninges of Brain and Spinal Cord

I. Dura mater

II. Arachnoid

III. Pia Mater

Section 2.. Blood Vessels of Brain and Spinal Cord

    . Arteries of Brain

. Veins of Brain

. Blood Vessels of Spinal Cord

Section3. Circulation of the Cerebrospinal Fluid

Section 4.  Brain Barriers

. Morphologic Basis for Blood-Brain Barrier

. Morphologic Basis for Blood-Cerebrospinal Fluid Barrier

. Morphologic Basis for Cerebrospinal Fluid-Brain Barrier

Chapter 5  Peripheral Nervous System

Section 1  Spinal Nerves

. Anterior Branches of Thoracic Nerves

. Cervical Plexus

. Brachial Plexus

. Lumbar Plexus

. Sacral Plexus

Section 2  Cranial Nerves

. Sensory Cranial Nerves

. Motor Cranial Nerves

. Mixed Cranial Nerves

Section 3  Autonomic  Nervous  System

I. Visceral Efferent Nerve

II. Visceral Afferent Nerves

III. Central Centers of Visceral Nerves

IV. Referred Pain

 

part  NERVOUS  SYSTEM   

Introduction

 

The nervous system controls and coordinates most of the activities of the body, matching them to the continuously changing circumstances of the world around. In order to carry out these functions, the nervous system monitors events in the external environment and within the body, coordinates all this information and matches it against past experience, and instructs other systems, such as somatic muscle, to produce an appropriate response. This response will in turn alter the information coming from the body and the external environment.

Nervous system can be divided into peripheral nervous system and central nervous system(Fig-1).

              

1. Peripheral nervous system (PNS) is formed by the cranial and spinal nerves and the peripheral part of the visceral nervous system. it collects the information from specialized sensory receptors throughout the body and transmits this information to the central nervous system. The peripheral nervous system also carries commands from the central nervous system to effectors.

2. Central nervous system (CNS) comprising the brain and spinal cord is wrapped in protective coverings, the former lies in the cranial cavity, and the latter located in the vertebral canal.

Fig-1. The structure of the CNS and the PNS.

           Chapter 1  General Description

 

IComposition of Nervous System

The nervous system is basically formed by the nervous tissue which consists of two principal cellular constituents, the nerve cells or neurons, and neuroglial cells or glia. The neuron is the structural and functional unit of the nervous system and the glia provide structural and metabolic support for neurons.

)  Neurons

1. Structure of neurons (Fig-1-1).

Although neurons are different in shapes and sizes, each has four morphologically specialized regions (Fig-2): cell body, dendrites, axon, and axon terminals. A neuron can be defined, functionally, as 3 zones: Receptor zone — (cell body and dendrites) at where the afferent or incoming impulses arrive. Conducting zone — (axon) specialized for conduction of the nervous impulse. Effector zone— (axon terminals) where electrical or chemical signals are transmitted across specialized junction (synapse).

part  nervous system

 Introduction

Chapter 1  General Description

. Composition of Nervous System

Reflex and reflex archs

Terminology

Chapter 2  Central Nervous System

Section 1  Spinal Cord

. External Features of Spinal Cord

. Internal Structure of Spinal Cord

Section 2   Brain Stem

I.  External Features

II.  Internal Structure 

III.  Transverse Sections of Brain Stem

IV  1esions of Brain Stem

Section 3  Cerebellum

I.  Lobes of Cerebellum

II.  Cerebellar Cortex

III.  Central Nuclei of Cerebellum

IV.  Cerebellar Cortex and Cerebellar Peduncles

V. Functions

Section4.  Diencephalon

I .  Dorsal Thalamus

II .  Epithalamus

III.  Subthalamus

IV.  Metathalamus

V.  Hypothalamus

VI. Third Ventricle

Section 5.  Telencephalon

I .  External Features

II .  Limbic System

III.  Cerebral Cortex

IV.  Internal Structures

Chapter 3  Nervous Pathways

Section 1.. Sensory (Ascending)Pathways

.Superficial Sensory Pathways

.Deep Sensory (or the proprioceptive) Pathways

. Visual Pathways

. Auditory Pathway

. Equilibratory Pathway

Section 2.. Motor (Descending)Pathways

. Pyramidal System

. Extrapyramidal System

C    Meninges and Blood Vessels of Brain and Spinal Cord, and the Cerebrospinal Fluid

Section 1... Meninges of Brain and Spinal Cord

I. Dura mater

II. Arachnoid

III. Pia Mater

Section 2.. Blood Vessels of Brain and Spinal Cord

    . Arteries of Brain

. Veins of Brain

. Blood Vessels of Spinal Cord

Section3. Circulation of the Cerebrospinal Fluid

Section 4.  Brain Barriers

. Morphologic Basis for Blood-Brain Barrier

. Morphologic Basis for Blood-Cerebrospinal Fluid Barrier

. Morphologic Basis for Cerebrospinal Fluid-Brain Barrier

Chapter 5  Peripheral Nervous System

Section 1  Spinal Nerves

. Anterior Branches of Thoracic Nerves

. Cervical Plexus

. Brachial Plexus

. Lumbar Plexus

. Sacral Plexus

Section 2  Cranial Nerves

. Sensory Cranial Nerves

. Motor Cranial Nerves

. Mixed Cranial Nerves

Section 3  Autonomic  Nervous  System

I. Visceral Efferent Nerve

II. Visceral Afferent Nerves

III. Central Centers of Visceral Nerves

IV. Referred Pain

 

part  NERVOUS  SYSTEM   

Introduction

 

The nervous system controls and coordinates most of the activities of the body, matching them to the continuously changing circumstances of the world around. In order to carry out these functions, the nervous system monitors events in the external environment and within the body, coordinates all this information and matches it against past experience, and instructs other systems, such as somatic muscle, to produce an appropriate response. This response will in turn alter the information coming from the body and the external environment.

Nervous system can be divided into peripheral nervous system and central nervous system(Fig-1).

              

1. Peripheral nervous system (PNS) is formed by the cranial and spinal nerves and the peripheral part of the visceral nervous system. it collects the information from specialized sensory receptors throughout the body and transmits this information to the central nervous system. The peripheral nervous system also carries commands from the central nervous system to effectors.

2. Central nervous system (CNS) comprising the brain and spinal cordis wrapped in protective coverings, the former lies in the cranial cavity, and the latter located in the vertebral canal.

Fig-1. The structure of the CNS and the PNS.

           Chapter 1  General Description

 

IComposition of Nervous System

The nervous system is basically formed by the nervous tissue which consists of two principal cellular constituents, the nerve cells or neurons, and neuroglial cells or glia. The neuron is the structural and functional unit of the nervous system and the glia provide structural and metabolic support for neurons.

)  Neurons

1. Structure of neurons (Fig-1-1).

Although neurons are different in shapes and sizes, each has four morphologically specialized regions (Fig-2): cell body, dendrites, axon, and axon terminals. A neuron can be defined, functionally, as 3 zones: Receptor zone( — (cell body and dendrites) at where the afferent or incoming impulses arrive. Conducting zone— (axon) specialized for conduction of the nervous impulse. Effector zone — (axon terminals) where electrical or chemical signals are transmitted across specialized junction (synapse).

Fig-1-1.  A schematic nerve cell is shown, illustrating the dendrites,

cell body, axon, and axon terminals.

 

Fig-1-1.  A schematic nerve cell is shown, illustrating the dendrites,

cell body, axon, and axon terminals.

 (1) Cell body

The cell body, or perikaryon is the metabolic and genetic center of a neuron (Fig.-1-1,2). It contains a nucleus with a prominent nucleolus. After appropriate staining procedures, one can demonstrate within the cytoplasm of nerve cells neurofibrils, chromophil substance(Nissl bodies),  Golgi apparatus, mitochondria, at times a central body, and various inclusions such as pigment, and lipids. Neurofibrils are uniquely characteristic of nerve cells, whereas the other cytoplasmic constituents are observed in other tissue cells. Most of these constituents are visualized simultaneously with the electron microscope.

                 Fig VI-1-2

(2)Dendrites

Most neurons usually have many dendrites. The cytoplasm of dendrites resembles that of the perikaryon, with granular endoplasmic reticulum(Nissl bodies) in their proximal trunks and at points of branching. The surface area of the dendrites is usually far larger than that of the cell body. In some neurons, the smaller branches bear large numbers of minute mushroom-shaped projections, called dendritic spines, which receive the nerve impulses coming from the other neurons(Fig.-1-1).

(3) Axons and axon terminals

A neuron has a single axon, which is a cylindrical tube of cytoplasm covered by a membrane, the axolemma. The axon conducts electrical signals from the cell body to the axon terminals. In large neurons, the initial segment of axon form a cone-shaped portion the axon hillock, which is free of Nissl bodies. Distally each axon breaks up into simple or extensive terminal arborizations which end as synaptic terminals (also known as terminal button) in contact with other cells(Figs-1-1,3)to form the synapses. Collateral branches  may be given off from the axon.

         Figs-1-1,3

2Classification of neurons(Figs-1-3,4)

(1). Based on number of processes arising from cell body, neurons are classed as unipolar(or pseudounipolar), bipolar, and multipolar. The multipolar neurons is different greatly in shape.

(2). Based on length of axons, neurons are also classified into three types(Fig-1-4): Golgi typeneurons have long axons. The longest axons in the central nervous system (CNS) of humans extend from the cerebral cortex to the caudal tip of the spinal cord, a distance of 50—70 cm.Golgi typeneurons  have short axons. The shortest axons terminate only a few micra from the perikaryon Amacrine neurons, an unusual neuron type, lack axons.

                  Fig-1-4. Variety of neuron shapes

(3). Based on their function, all neurons fall into three types(Fig-1-5):

Sensory neurons receive stimuli and transmit afferent impulse to the CNS Association neurons(also called nterneurons) lies in the central nervous system forming the complex nervous circuits. Motoneurons deliver efferent impulses from the central nervous system to the peripheral nervous system (PNS) to activate effectors.

(4) Based on classification of neurotransmitters chemistry, neurons may also grouped as monoaminergic, cholinergic, amino acidergic, peptidergic, and so on.

Fig-1-2. The diaphragm of neuron cell body

Fig-1-3. Morphological classification of neurons: a. bipolar neuron; b. unipolar neuron; c. multipolar neuron.

Fig-1-5. Functional classification of neurons: A. a sensory neuron;

 B. a association neurons  C. a motor neuron.

) Synapses and Neurotransmitters

Communication between neurons usually occurs at specialized junctions called synapses. where excitation is transmitted from one nerve cell to another. We call the neuron sending information the presynaptic neuron and the other is called the postsynaptic neuron which receives the information.

1.  synapses

Synapses can be formed between almost any regions of the two participating neurons. The most common type of synapses occurs between a terminal of an axonal branch of a neuron and a dendrite or a soma of another(Figs-1-1,5). The synapses may be divided into two kinds: the chemical synapses and electrical synapses. The chemical synapses is the most common type in the mammalian nervous system, which transmits the nervous impulse by the chemical substance—Neurotransmitters. Electrical synapses are only present in invertebrates and fishes. The chemical synapses can be classified, according to the neuronal regions that participate in forming the synapse, into axodendritic synapses and axosomatic synapses (most common), or, less often, dendrodendritic synapses and axoaxonal synapses.

Figs-1-6

 

Typical chemical synapses may be divided into 3 parts(Figs-1-6) the presynaptic part with the dense thickening presynaptic membrane;② the postsynaptic part with the postsynaptic membrane(;③the synaptic clefta narrow gap about 20 nm wide which separates the presynaptic and postsynaptic membrane. The presynaptic part contains numerous vesicles, Synaptic vesicles in which the chemical substances --neurotransmitter is present.

2. Neurotransmitters

Neurotransmitters are small molecular weight compounds; among these are acetylcholine  and monoaminergic compounds such as norepinephrine and serotonin. Amino acids(e.g., glutamate, glycine, and γ-aminobutyric acidγ-, or GABA) and larger molecules, such as peptides (e.g., enkephalin and substance P) also function as neurotransmitters. When an impulse arrives at the presynaptic element, the neurotransmitter diffuses across the synaptic cleft and bind to the receptor molecules in the postsynaptic membrane. As a result, the postsynaptic neuron is activated and the impulse is conducted from one neuron to the others.

 

II.Reflex and Reflex arcs

1. Basic components of reflex arc

A reflex arc is the basic functional unit of the nervous system. The reflex arc has five basic components: a receptor respond to stimuli and produce nervous impulse, a sensory neuron transmits the impulse to the CNS, where the axons usually synapse with interneurons; which synapse with motor neurons in the CNS; a motor neuron carry action potentials out of the CNS and through the PNS to effector organs, such as muscles or glands, respond to the action potentials(Fig-1- 7).

The response produced by the reflex arc is called a reflex.

Fig-1-7. A schematic monosynaptic reflex arc.

 

III. Terminology

1. Nerve fiber

A nerve fiber in the central nervous system consists of the axon and the surrounding myelin sheath or of the axon only in the case of unmyelinated fibers. In the peripheral nervous system both myelinated and unmyelinated fibers have, in addition, an outer delicate nucleated membrane, the sheath of Schwann or nurolemmal sheath. The peripheral myelinated fiber is structurally the most differentiated, consisting of axon, myelin and sheath of Schwann(Fig.-1- 8).

             

                   Fig.-1- 8

Myelinated fibers conduct more rapidly than unmyelinated ones. Speed of conduction is proportional to the diameter of the fiber and the thickness of the myelin sheath. The myelin sheath may be regarded as insulation, while the extracellular space at the nodes of Ranvier and the periaxonal space provide ready avenues for ionic diffusion.

2.  Nucleus and grey matter

A nucleus is a aggregation of neuronal cell bodies and dendrites, of more or less similar shape and function, located inside the central nervous system. Nuclei is various in sizes and shapes, commonly spherical and oval, and sometimes in small flattened sheets.

The neuronal cell bodies and dendrites may form more extensive layers or masses in the central nervous system collectively called grey matter. The grey matter looks grey because it consists of masses of nerve cell bodies that contain pigment and organelles. Neuronal dendrites and synaptic activity are mostly confined to nuclei and areas of grey matter.

3. Tracts and white matter

Bundles of nerve fibres in the central nervous system tend to be grouped to form the tracts, or fasciculi. In the brain and spinal cord, concentrations of tracts constitute the white matter, so called because the axons are often ensheathed in myelin which glistens white in the fresh state.

4.  Cortex and medullary substance

The continuous sheet of grey matter covering the surface of the cerebrum and cerebellum is called the cortex.The medullary substance, or medulla is a central core of white matter beneath the cortex of the cerebrum and cerebellum.

5. Ganglion

In the peripheral nervous systemPNS, the cell bodies are grouped together to form the ganglia. Sensory ganglion cells in dorsal roots of spinal nerves and some cranial nerves give off both central and peripheral processes, and do not have synapses on their cell bodies, whilst ganglionic neurons of the viscersl nervous system receive synaptic contacts from various sources.

6.  Nerve

In the peripheral nervous system , a nerve is a bundle of nerve fibers together with supporting connective tissue. Most of nerves have a whitish appearance because of their myelin content. There are three connective tissue sheaths in peripheral nerves. They are, from inside out, the endoneurium, perineurium, and epineurium. Each nerve fiber is surrounded by a re-enforcing sheath of delicate connective tissue, the endoneurium. It is continuous with the more abundant connective tissue of the perineurium, which envelops both small and large bundles of fibers within a peripheral nerve trunk and divides the nerve into fascicles. The epineurium is the outermost sheath. This dense, collagenous layer forms an external connective tissue ensheathment for all peripheral nerves.

 

Huang Yaode : Shanghai Second Medical University