Introduction And Spinal Cord

About the function of the nervous system 1.The reaction of fighting for food 2.The reaction of flight from enemy 3.The reaction of pursuit of mating

The nervous system is the master controlling system of the body. It has three main functions: 1) It monitors changes occurring both inside and outside the body by means of millions of receptors; 2) It processes and interprets the sensory input and makes decisions about what should be done – integration; 3) It dictates a response to activate the effector organs by means of motor output. Neuroanatomy Neurophysiology Neuropathology Neurophamocology Neurobiology Neuroscience

Nervous system

神经系统

Part 6 Introduction Major divisions of the nervous system: Central nervous system CNS 中枢神经系统 consisting of brain and spinal cord, is the integrating and command center of the nervous system.

Peripheral nervous system 系统

PNS

周围神经

consisting of cranial and spinal nerves extending from brain and spinal cord, serves as communication lines linking all regions of the body to CNS

Sensory (afferent )part and motor (efferent )part of nervous system Somatic nerves 躯体神经 Visceral nerves 内脏神经

Visceral nerves

内脏神经

Autonomic nervous system ANS is the system of motor neurons that innervate the smooth muscle, cardiac muscle and glands, which consisting of two parts:

Sympathatic nerve 交感神经 Parasympathatic nerve 副交感神经 Both divisions innervate the same visceral organs but cause opposite effects The visceral nerves also contain sensory part which monitor tretch, temerature, chemical changs, and irritation within the visceral organs

DR. CAMILLO GOLGI (1843-1926)

Born in Corteno (Brescia), Italy, Golgi received his education at PAVIA (Italy) and then became assistant to the great Cesar Lombroso at the Institute di Patologia Generale. His work on pellagra early and psammomas later brought him great recognition but the development of the Golgi method to stain neuroglia achieved for him permanent fame. His studies on gliomas were monumental. Together with Santiago Ramon of Cajal (1852-1934) when he even denunciated, they jointly received the Nobel Prize in 1906.

Santiago Ramon y Cajal

Chapter 1 Gereral Description Neuron

nerve cell

The basic functional unit of the nervous system; a highly specialized cell Cell body (soma): Nissl bodies (chromophil substance) Neurofibrils Dendrite: dendritic spines Axon: synaptic terminals

Nissl body: the material consisting of granular endoplasmic reticulum and ribosomes that occurs in nerve cell bodies and dendrites.

Neurofibril: a filamentous structure seen with the light microscope in the nerve cell's body, dendrites, axon, and sometimes synaptic endings,

Classification of neurons 1.Unipolar, bipolar and multipolar neuron 2.Sensory neurons, interneurons and motoneuron 3.Golgi typeⅠandⅡ, Amacrine neurons 4.Monoaminergic, cholinergic and peptidergic neurons

Neuroglial cell

(Neuroglia)

Supporting cells that interact with neurons and regulate the extracellular environment, provide defense against pathogens and perform repairs within neural tissue

Oligodendrocyte

Astrocyte

Microglia Ependymal cell

Terminology Grey matter: neural tissue dominated by neurons’ soma and dendrites Cortex: a layer of grey matter at the surface of the brain, cerebrum and cerebellum Nucleus: a group of nerve cell bodies in the brain or spinal cord that can be demarcated from neighboring groups on the basis of differences in cell type White matter: neural tissue dominated by myelinated axons Medullary substance: consisting of the lipid material present in the myelin sheath of nerve fibers, lies deep to the cortex in cerebrum and cerebellum

Tract (fasciculus):

a bundle of axons within CNS that share a common origin, destination and function

Ganglion:

a distinct collection of sensory or postganglionic cell bodies within PNS

Nerve fiber:

the axon of a nerve cell, ensheathed by oligodendroglia cells in brain and spinal cord, and by Schwann cells in peripheral nerves.

Nerve:

a bundle of axons in PNS

Chapter 2 Section 1

Central Nervous system spinal cord

脊髓

Ⅰ. external Features: 1.Enlargments cervical enlargement 颈膨大 Lumbosacral enlargment 腰骶膨大 2.external longitudinal fissures and sulci anterior median fissure 前正中裂 posterior mediansulcus 后正中沟 anterolateral sulcus 前外侧沟 posterolateral sulcus 后外侧沟 Conus medullaris 脊髓圆锥 Filum terminale 终丝

3.Segments of the spinal cord The short part of spinal cord associated with a pair of spinal nerves is called a segment of spinal cord; A segment correspond to the dorsal and ventral roots of a pair of spinal nerves 31 segments of spinal cord: 8 cervical segments 12 thoracic segments 5 lumbar segments 5 sacral segments 1 coccygeal segemnts

4.Location of spinal cord in relation to vertebral column 1)

In the third month of fetal life, the cord is as long as the vertebral canal;

2)

At birth, the cord ends at the level of the 3th lumbar vertebra;

3)

In the adult, the cord ends at the level of the lower border of 1st lumbar vertebral body;

Corresponding position of cord to vertebral bodies segments of cord

vertebral bodies

C1-4

C1-4

C5-T4

C4-T3

T5-8

T3-6

T9-12

T6-9

L1-5

T10-12

S1-4,Co1

L1

Ⅱ.Internal structure of the spinal cord gray matter

灰质

anterior horn 前角 posterior horn 后角 lateral horn 侧角 intermediate zone 中间带 anterior gray commissure 灰质前连合 Posterior gray commissure 灰质后连合

white matter

白质

anterior funiculus 前索 posterior funiculus 后索 lateral funiculus 外侧索 anterior white commissure 白质前连合 reticular formation 网状结构

central canal

中央管

Relationship between the grey matter and the spinal nerve: 1)posterior horn links with sensory fibers; 2)anterior horn links with somatic motor fibers; 3)lateral horn links with sympathetic motor fibers

The nuclei located in

grey matter

Posteromarginal nucleus

Posteromarginal N. 后角边缘核 receive incoming fibers of dorsal root Substantia gelatinosa 胶状质 receive fibers of pain and

Substantia gelatinosa

Nucleus proprius

temperature sensation Nucleus proprius 后角固有核 receive all sensory modalities Thoracic nucleus 胸核 give fibers to dorsal spinocerebellar tract in segments T1-L3 Motoneurons of anterior horn

Thoracic nucleus

前角运动神经元

αmotoneuron innervate skeletal muscles γmotoneuron innervate intrafusal muscle

Medial motor neurons Medial motor neuron Lateral motor neuron and leg

Lateral motor neurons axial muscles distal muscles of arm

Lamina of Rexed

a division of the gray matter of the spinal cord into nine laminae (I–IX) and a gray area around the central canal (area X) based on cytoarchitectural features; the dorsal (posterior) horn is composed of laminae I– VI, the intermediate zone of lamina VII, and the ventral horn of laminae VIII and IX;

General correlation of laminae with some of the major nuclei: I ： posteromarginal nucleus; II ： substantia gelatinosa; III and IV ： nucleus proprius; V and VI ： sometimes described as containing the spinal reticular formation; VII ： Clarke nucleus (thoracic nucleus), intermediolateral cell column; VIII ： commissural nuclei, interneurons; IX ： motor nuclei of ventral horn.

All fibers in the cord are assigned to 5 groups: 1)affenrent fibers 2)efferent fibers 3)intersegmental fibers 4)long ascending fibers conducting afferent impulses to supraspinal levels 5)long descending fibers from supraspinal souces to synapse with spinal neurons

Fibers of the type 4 and 5 form longitudinal bundles with more or less distinct demarcation; Fiber bundles having the same origin, course and termination are known as tracts or fasciculi occupying particular area

Organization of the dorsal root and its relationship with the main ascending tracts: 1)lateral division convey impulses related to pain, thermal and light touch sense, pain and thermal fibers enter lateral spinothalamic tract, light touch fibers enter anterior spinothalamic tract; 2)medial division convey sensation of fine touch, movement and proprioception, which enter posterior funiculus to form gracile and cuneate fasciculi

Fasciculus gracilis FG

薄束

fasciculus cuneatus FC

楔束

Dorsal column system

Position: within the posterior funiculus / FG in most medial part; FC lateral to FG; arising from the thick and large fibers of the medial part of dorsal root and ending in the gracile and cuneate nuclei in the medulla Function: convey sensation of fine touch, vibration, two-point discrimination, proprioception and position sense FG conducts input from the lower half of the body; FC transmits input from the upper half of the body. Thoracic 4 is the demarcation for FG and FC Somatotopic organization: Fibers are arranged in an orderly fashion from medial to lateral in relation to the regions of the body from down up Fasciculus gracilis and

Spinothalamic tract STT

脊髓丘脑束

Position: anterior STT in the anterior funiculus fuses laterally with lateral STT in the lateral funiculus; Function: 1) anterior STT convey impulses of light touch and pressure sensations ; 2) lateral STT conducts pain and temperature sensibilities Some anatomical details: 1) all the fibers come from the lateral part of the dorsal root; 2) all primary fibers relay in laminae Ⅰ and Ⅵ-Ⅷ; 3) majority of fibers cross the median line in anterior white commissure to contralateral tract; 4) decussation is completed in the segment above the entrance of the dorsal root Somatotopic organization: fibers from lower part of body is sited in lateral part of the tract;fibers from upper part in medial part Spinothalamic tract

Spinocerebellar tracts SCT

脊髓小脑

束

Posterior SCT: originates from the ipsilateral dorsal nucleus / ascends in lateral funiculus / transmits subconscious proprioceptive impulse via inferior cerebellar peduncle Anterior SCT: originates from neurons spreading in the intermediate zone / lies anterior to pSCT / relay internal feedback signals to cerebellum via superior cerebellar peduncle

Spinocerebellar tracts

Corticospinal tract CST

皮质脊髓束 descending projection pathway for controlling voluntary movements / arise mainly from precentral motor cortex and premotor area / majority of fibers cross over to form lateral CST and uncrossed fibers form anterior CST Lateral CST: ends primarily in lateral portion of the intermediate zone and anterior horn of the cervical and lumbosacral enlargment to contral distal limb muscles / somatotopic organization: fibers controlling the lowest part of the body are most laterally placed Anterior CST: descends in anterior funiculus and extends only to the upper thoracic cord / ends in the same area with lateral CST to control axial and girdle muscles of the upper part of the body bilaterally

Corticospinal tract

Rubrospinal tract: facilitates flexor muscles and inhibits extensor ones Vestibulospinal tract: excite motor neurons of extensor muscles and inhibit those of flexor muscles Reticulospinal tract: control axial and girdle muscles and regulate posture; help control automatic movements Medial longitudinal fasciculus: help control head position Tectospinal tract: coordinate head movements with eye movements, maybe cause turning in response to sudden visual or auditory stimuli

Minor descending tracts