-1-

Chapter 17 Central Nervous System

The spinal cord Location And External Features Internal Structure the manifestation of spinal reflex and post-trauma Functions Of The Spinal Cord

Brain

Nervous system

-2-

shape ： two enlargement ： cervical enlargement⑸ lumbosacral enlargement⑹

Location And External Featuresposition ： lie in vertebral canal The superior extremity is linked with medulla oblongata at the level of great occipital foramen. The inferior extremity is at the level of the inferior border of first body of lumber vertebra in adult.

Spinal cord

anterior median fissure ⑴posterior median sulcus ⑵anterolateral sulci ⑶posterolateral sulci ⑷

stripes of sulcus ：

⑴ ⑵⑶

⑷

⑸

⑹

-3-

Conus medullaris ⑴Filum terminale ⑵Cauda equina⑶ Spinal nerve （ 31 pairs ）Anterior root ⑷ （ motor ）Posterior root⑸ （ sense ）

⑴⑵⑶

⑷⑸

⑵

-4-

C1 - C4

C5 - T4

TIII - TVI

TVI - TIX

TX - TXII

LI

T5 - T8

T9 - T12

L1 - L5

S1 - Co1

CIV - TIII

CI - CIV - 0

- 1

- 2

- 3

The relationship with vertebrae

vertebraespinal cord

31 segments ： C8 、 T12 、 L5 、 S5 、 Co1

The spinal segment refers to a region of the spinal cord from which a pair of spinal nerves arises.

-5-

central canal anterior (ventral) horn or anterior column posterior (dorsal) horn or posterior column lateral horn or lateral column intermediate zone central gray posterior gray commissure anterior gray commissure white matter anterior funiculus lateral funiculus posterior funiculus anterior white commissurereticular formation

terminal ventricle

Internal Structure

-6-

Lamina ⅢLamina Ⅳ

Lamina —Ⅰ marginal layer （ areas spongiosa ）Lamina —Ⅱ substantia gelatinosa

Laminas of the gray matter

Rexed layers

Lamina ⅤLamina Ⅵ

receive the afferent fibers of proprioceptive sense and regulate movement

nucleus proprius

Lamina Ⅶ

intermediomedial nucleus——is related to visceral sensory intermediolateral nucleus——is related to visceral motorthoracic nucleus （ Clark’s column ）— unconscious proprioceptive sense sacral parasympathetic nucleus—is correspond to layer at the Ⅶsegment S2 － 4 ， visceral motor

Lamina —Ⅷ interneuron, effect the γ and α motor neuron

-7-

Layer — motor neuron of anterior hornⅨ medial nucleus of anterior horn ： trunk muscle lateral nucleus of anterior horn ： limb muscle α-motor nerve ⑴ ： dominate the extrafusal muscle fiber of straddling joint→joint movement γ-motor nerve ⑵ ： dominate intrafusal fiber→regulate muscular tension Renshaw cell⑶： receive α- axon collateral of motor nerve and send out branches and form reverse feedback loop with it.

layer — central grayⅩ ： receive some posterior root fiber

Ⅹ⑴ ⑵

⑶

-8-

Laminas NucleiI posteriomarginal nucleusII substantia gelatinosaIII, IV nucleus propriusV reticular nucleusVI base of posterior columnVII thoracic nucleus, intermediomedial nucleus, intermediolateral nucleus, sacral parasympathetic nucleusVIII, IX medial motor neuron column, lateral motor neuron columnX central gray matter

The relationship between the laminas and the nuclei of the spinal cord

-9-

Tracts of the Spinal Cord

Ascending Tracts

fasciculus gracilis ⑴ below T5

fasciculus cuneatus ⑵ above T4 —conduct conscious proprioceptive sense

⑴⑵

-10-

posterior spinocerebellar tract

anterior spinocerebellar tract —conduct unconscious proprioceptive sensespinothalamic tract lateral spinothalamic tract ⑴ —conduct crude sense of touch and pressure sensation anterior spinothalamic tract ⑵ —conduct sense of pain and warm

direct cerebellar tract

⑴

⑵

-11-

Descending Tracts

corticospinal tract ： body movement lateral corticospinal tract ⑴ anterior corticospinal tract ⑵ anterolateral corticospinal tract (of Barnes) rubrospinal tract ： flexor excited vestibulospinal tract ： extensor excited reticulospinal tract ： motor control of proximal muscle of trunk and limbs tectospinal tract ： excite the cervical muscle of opposite side, inhibit cervical muscle of homonymy medial longitudinal fasciculus ： regulating the ocular movement and head position

-12-

Functions of the Spinal Cord

Conduction pathway ；reflex centre 。spinal reflex

somatic reflexes —reflexes that result in the contraction of skeletal muscles superficial (skin and mucous membrane) reflexes and deep (myotatic) reflexes etcvisceral reflexes —the contraction of smooth or cardiac muscle or secretion by glandssuch as carotid sinus, bladder and rectal reflex,etc.

1 ） receptor ， 2 ） afferent neuron ， 3 ） interneurons neuron ，4 ） efferent ， 5 ） effector

The simple reflex arc includes

-13-

Stretch Reflexes

muscle 、 tendon

posterior roots

α-motor neurons

anterior roots

Muscle contraction

stretch reflex （ tendon reflexes ）：

-14-

Flexor Reflexes

skin

posterior roots

posterior horn

interneurons neuron

α-motor neurons

Muscle contraction

anterior roots

-15-

Clinical Consideration

The spinal cord transection spinal shock Hemisection of the spinal cord Brown-Se´quard syndrome Lesion of anterior horn of the spinal cord flaccid paralysis Lesion around the central gray matter peripheral dissociation