Nervous System SHANDONG UNIVERSITY liu Zhiyu Introduction 1

Nervous System SHANDONG UNIVERSITY liu Zhiyu

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

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

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

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

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

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 脊髓 Position: p lies in vertebral canal continuous with medulla oblongata at level of foramen magnum p p ends at the lower border of L 1; p at birth , ends at the level of L 3

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

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

The spinal cord 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 : Cervical segment 8 Thoracic segment 12 Lumbar egment 5 Sacral segment 5 coccygeal segment 1

The spinal cord Table 1 Relationship of segments of spinal cord to vertebrae Spinal segments Vertebral levels C 1 ~ C 4 Lie opposite the corresponding C 5~T 4 1 lower in number than corresponding vertebrae T 5 ~ T 8 T 9 ~T 12 vertebrae 2 lower in number than corresponding vertebrae 3 lower in number than corresponding vertebrae Lumber segments T 10~T 12 Sacral and coccygeal segments L 1

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

The spinal cord Gray matter 1) Posterior horn (column): Posteromarginal nucleus Substantia gelatinosa Nucleus proprius Nucleus thoracicus (dorsalis) in segments C 8~L 3

Gray matter 2) Intermediate zone Intermediaolateral nucleus: lies in segments T 1~L 3, containing sympathetic preganglionic neurons n n Sacral parasympathetic nucleus lies in segments S 2~S 4 n Intermediomedial nucleus for sensation of viscera

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

Gray matter 3) Anterior horn (column): 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

Gray matter The laminas: Spinal cord gray matter is arranged in layers, there are 10 Rexed’s lamina: 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 spinal cord Table 2. Important Subdivision of Spinal Cord Gray Matter Region Posterior horn Intermediate zone Lamina Nucleus Ⅰ Marginal layer Ⅱ Substantia gelatinosa Ⅲ, Ⅳ Nucleus proprius Ⅶ Nucleus thoracicus (C 8~L 3) Intermediolateral nucleus (T 1~L 3) Sacral parasympathetic nucleus (S 2~S 4) Intermediomedial nucleus Anterior horn Ⅸ Motor neuron

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

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

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

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

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

Ascending tracts n. Fasciculus gracili Arises from spinal ganglion cell below T 5 ； Terminates the Gracile nucleus n. Fasciculus cuneatus Arises from spinal ganglion cell above T 4； Terminates the Cuneate nucleus

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

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

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

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

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

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

Ascending tracts Tract Site of origin Fasciculus gracilis Spinal ganglia below segment T 5 Posterior Gracile nucleus Fasciculus cuneatus Spinal ganglia above segment T 4 Cuneate nucleus Posterior spinocerebellar Homolateral nucleus thoracicus Anterior spinocerebellar Spinothalamic Funiculu s Lateral Termination Cerebellum Contralateral Laminae Ⅴ~Ⅶ Laminae Ⅰ, Ⅳ~Ⅶ Lateral and anterior Dorsal thalamus Function Convey proprioceptive and fine touch sensation of trunk and limbs Unconscious proprioception from lower limb and lower portion of trunk Pain, temperature and simple touch sensation of trunk and limbs

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

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

Rubrospinal 红核脊髓束

Two-Point Discrimination

Descending Motor Pathways

The spinal cord ① Ascending tracts: Tract Fasciculus Gracilis Fasciculus Cuneatus origin Spinal ganglia below T 5 Spinal ganglia above T 4 position Posterior Funiculus Termination Gracile nucleus Function Proprioceptive and fine touch Cuneate nucleus sensation

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