Nervous System SHANDONG UNIVERSITY liu Zhiyu

Introduction Brain Stem Telencephalon Diencephalon Cerebellum Midbrain Pons Medulla oblongata 1. Divisions of nervous system Central nervous system (CNS) Peripheral nervous system (PNS): Spinal cord (1) Central nervous system (CNS) Brain :

(2) Peripheral nervous system (PNS): Cranial n. (12 pairs) Spinal n. (31 pairs) Visceral n. : Introduction Visceral sensory n. Visceral motor n.: Sympathetic part Parasympathetic part

2. Basic terminology in nervous system : 常用术语 (1) CNS: 1) Gray matter collection of nerve cell bodies and their dendrites, Introduction the outer layer of gray matter in cerebrum and cerebellum A group of nerve cell bodies which have the same shape and function. Cortex Nucleus

2) White matter collection of nerve fibers, white color during fresh condition Introduction a central core of white matter beneath cortex of cerebrum and cerebellum a bundle of nerve fibers which have the same origin, termination, and function Medulla Fasciculus ( tract ):

3) Reticular formation: a field of intermingled grey and white matter, and with larger or smaller groups of nerve cells occupying the meshes. Introduction

Introduction (2) PNS 1) Ganglion: a collection of neuron cell bodies outside the CNS 2) Nerve: a bundle of nerve fibers held together by connective tissue sheath

The Spinal Cord The Spinal Cord

The Spinal Cord 脊髓 Position:  lies in vertebral canal  continuous with medulla oblongata at level of foramen magnum  ends at the lower border of L1;  at birth, ends at the level of L3

2. External features ＊ A long cylindrical structure slightly flattened anteroposteriorly ＊ conus medullaris ＊ filum terminale The Spinal Cord

Two enlargements ⑴ Cervical enlargement: ⑵ Lumbosacral enlargement The Spinal Cord Fissure and sulci: ⑴ Anterior median fissure ⑵ Posterior median sulcus ⑶ Anterolateral sulcus ⑷ Posterolateral sulcus

3. segments of spinal cord A portion of the spinal cord that gives attachment to a pair of spinal n. constitutes a segment. 31 segments : The spinal cord Cervical segment 8 Thoracic segment 12 Lumbar egment 5 Sacral segment 5 coccygeal segment 1

The spinal cord Spinal segments Vertebral levels T10~T12 L1 3 lower in number than corresponding vertebrae 2 lower in number than corresponding vertebrae 1 lower in number than corresponding vertebrae Lie opposite the corresponding vertebrae Table 1 Relationship of segments of spinal cord to vertebrae C1 ~ C4 C5~T4 T5 ~ T8 T9 ~T12 Lumber segments Sacral and coccygeal segments

4. Internal structures (1) Central canal (2) Gray matter : The spinal cord Anterior horn (column) Posterior horn (column) Intermediate zone (3) White matter Anterior funiculus Lateral funiculus Posterior. Funiculus Ant. white commissure

Gray matter 1) Posterior horn (column): The spinal cord Posteromarginal nucleus Substantia gelatinosa Nucleus proprius Nucleus thoracicus (dorsalis) in segments C8~L3

Gray matter Sacral parasympathetic nucleus lies in segments S2~S4 Intermediomedial nucleus for sensation of viscera 2) Intermediate zone Intermediaolateral nucleus: lies in segments T1~L3, containing sympathetic preganglionic neurons

Gray matter ① α-motor neuron : larger multipolar neuron ② γ-motor neuron : smaller neuron, innervates intrafusal fibers regulating muscular tonus- 3) Anterior horn (column): contain motor neurons ③ Renshaw’s cell:

Gray matter Two groups of nuclei ① Medial nuclear group present in most segments of spinal cord, innervating axial muscles. ② Lateral nuclear group present only in cervical and lumbosacral enlargements, innervating limb muscles 3) Anterior horn (column):

Gray matter The posterior horn is formed by lamina Ⅰ to Ⅵ, The intermediate zone corresponding to lamina Ⅶ, The anterior horn is composed laminae Ⅷ and Ⅸ, lamina Ⅹ is the gray matter surrounding the central canal. The laminas: Spinal cord gray matter is arranged in layers, there are 10 Rexed’s lamina:

The spinal cord Region Lamina Nucleus Posterior horn Ⅰ Marginal layer Ⅱ Substantia gelatinosa Ⅲ, Ⅳ Nucleus proprius Intermediate zone Ⅶ Nucleus thoracicus (C8~L3) Intermediolateral nucleus (T1~L3) Sacral parasympathetic nucleus (S2~S4) Intermediomedial nucleus Anterior horn Ⅸ Motor neuron Table 2. Important Subdivision of Spinal Cord Gray Matter

White matter Three kinds of fibers descending fibers fasciculus proprius Ascending fibers

Ascending (Sensory) Pathways Conduct general somatic sensory impulses Chains of neurons composed of: – First-, second-, and third-order neurons three main ascending pathways – Dorsal column pathway – Spinothalamic pathway – spinocerebellar pathway

Ascending tracts Fasciculus cuneatus Posterior spinocerebellar tract （） Anterior spinocerebellar tract Spinothalamic tract Fasciculus gracilis

Ascending tracts Fasciculus Gracilis Fasciculus Cuneatus Conduct Proprioceptive and fine touch sensation

Fasciculus gracilis Fasciculus cuneatus Carries sensations of Two-point discrimination Proprioception Pressure Vibration Ascending tracts

Fasciculus gracili Ascending tracts Fasciculus cuneatus Arises from spinal ganglion cell below T5 ； Terminates the Gracile nucleus Arises from spinal ganglion cell above T4 ； Terminates the Cuneate nucleus

Ascending tracts Spinothalamic Tract Conduct Pain, temperature and simple touch sensation of trunk and limbs Origin : Laminae Ⅰ, Ⅳ ~ Ⅶ of spinal cord Termination: Dorsal thalamus

Ascending tracts Spinothalamic Tract Conduct Pain, temperature and simple touch sensation of trunk and limbs Origin: Laminae Ⅰ, Ⅳ ~ Ⅶ of spinal cord Termination: Dorsal thalamus

Ascending tracts Lateral Spinothalamic Tract Carries pain and temperature information Anterior Spinothalamic Tract Carries light touch, pressure Spinothalamic Spinothalamic tracts Lateral spinothalamic Tract Anterior spinothalamic Tract

Ascending tracts  Posterior. Spinocerebellar  Anterior. Spinocerebellar Origin : nucleus thoracicus Termination: Cerebellum Origin :Laminae Ⅴ ~ Ⅶ Termination: Cerebellum Carries subconscious proprioceptive sensations to cerebellum

dscending tracts Lateral Corticospinal Anterior corticospinal Corticospinal tract Arises from the cerebral cortex Terminates in the motor neurons of spinal cord, it divided into two tract:

dscending tracts 下行传导束 Lateral Corticospinal Anterior corticospinal Function: control somatic voluntary movement

Rubrospinal Tract Rubrospinal Tract Begins in the red nucleus, which is located at the midbrain and synapse with lower motor neurons in the Laminae Ⅴ ~ Ⅶ of the spinal cord. Injury to this structure impairs forearm and hand movements, but doesn’t greatly affect general body movement

Vestibulospinal Originate in the vestibular nuclei, and synapse with lower motor neurons Laminae Ⅶ ~ Ⅷ of the of the spinal cord. Receive major input from the vestibular nerve, and the cerebellum Laminae Ⅶ ~ Ⅷ

② another descending tracts: Reticulospinal Longitudinal fasciculus Tectospinal

The spinal cord ② Descending tracts Tracts origin position Termination Function Lateral Corticospinal Cerebral cortex Lateral Funiculus Laminae Ⅳ ~ Ⅸ Voluntary mov. Anterior corticospinal Cerebral cortexAnt. Funiculus Ant. horn Rubrospinal Red nucleus Lateral Funiculus Laminae Ⅴ ~ Ⅶ Excite flexor motor neurons Vestibulospinal Ant. Funiculus Laminae Ⅶ ~ Ⅷ Excite extensor motor neurons vestibular nuclei

The spinal cord ② Descending tracts Tracts origin position Termination Function Voluntary mov. Laminae Ⅶ ~ Ⅷ Reticulospinal Reticular formation Ant., lateral Funiculus Longitudinal fasciculus Vestibular nuclei Ant. Funiculus Laminae Ⅶ ~ Ⅷ Condinate neck with eye mov. ③ Fasciculus proprius Tectospinal Sup. colliculusAnt. Funiculus Laminae Ⅵ ~ Ⅷ Spinal cord Ant., pos. lateral Funiculus Spinal cordIntrinsic reflex mechanism of spinal cord Spinal cord

Ascending tracts Tract Site of origin Funiculu s TerminationFunction Fasciculus gracilis Spinal ganglia below segment T5 Posterior Gracile Gracile nucleus nucleus Convey proprioceptive and fine touch sensation of trunk and limbs Fasciculus cuneatus Spinal ganglia above segment T4 Cuneate Cuneate nucleus nucleus Posterior spinocerebellar Homolateral nucleus thoracicus LateralCerebellum Unconscious proprioception from lower limb and lower portion of trunk Anterior spinocerebellar Contralateral Laminae Ⅴ ~ Ⅶ Spinothalamic Laminae Ⅰ, Ⅳ ~ Ⅶ Lateral and anterior Dorsal Dorsal thalamus thalamus Pain, temperature and simple touch sensation of trunk and limbs

Tract Tract Site of origin TerminationFunction Lateral Lateral corticospinal corticospinal Cerebral cortex Laminae Ⅳ ~ Ⅸ Voluntary movement Anterior Anterior corticospinal corticospinal Cerebral cortex anterior horn Rubrospinal Rubrospinal Red nucleus Laminae Ⅶ ~ Ⅶ Excitatory of flexors Vestibulospinal Vestibulospinal Homolateral vestibular nuclei Laminae Ⅶ ~ Ⅷ Excitatory of extensors Reticulospinal Reticulospinal Reticular formation Laminae Ⅶ ~ Ⅷ Voluntary movement Fasciculus Fasciculus proprius proprius Spinal cord Intrinsic reflex mechanism of spinal cord Descending tracts

Function of spinal cord Reflexes ： the central of the reflex arc. Reflexes ： the central of the reflex arc. Conduction : Conduction : Convey afferent impulses to the brain; conduct efferent impulses from the brain to the effectors. Somatic reflex stretch reflex stretch reflex Visceral reflex Reflex of bladder Reflex of bladder Rectal emptying reflex Rectal emptying reflex

Rubrospinal 红核脊髓束

Two-Point Discrimination

Descending Motor Pathways

The spinal cord ① Ascending tracts: Tract origin position Termination Function Fasciculus Gracilis Spinal ganglia below T5 Posterior Funiculus Gracile nucleus Proprioceptive and fine touch sensation Fasciculus Cuneatus Spinal ganglia above T4 Cuneate nucleus

The spinal cord ① ascending tracts: Tracts origin position Termination Function Pain, temperature and simple touch sensation of trunk and limbs Spinothalamic Tract Laminae Ⅰ, Ⅳ ~ Ⅶ Lateral and ant. Funiculus Dorsal thalamus subconscious proprioception from lower part of trunk And lower limb Cerebellum nucleus thoracicus Laminae Ⅴ ~ Ⅶ Posterior. spinocerebellar Lateral Funiculus Anterior. spinocerebellar Cerebellum