The Nervous System

山东大学医学院 解剖教研室

李振华

Divisions

Central nervous system (CNS)

Peripheral nervous system (PNS)

Central nervous system (CN

S) Brain 脑

Telencephalon 端脑 Diencephalon 间脑 Cerebellum 小脑 Brain stem 脑干

Midbrain 中脑 Pons 脑桥 Medulla oblongata 延髓

Spinal cord 脊髓

Peripheral nervous system (PNS) Cranial n. (12 pairs) 脑神经

Spinal n. (31 pairs) 脊神经

Visceral n. 内脏神经 Visceral sensory n.

Visceral motor n

Sympathetic part 交感神经 Parasympathetic part 副交感神经

Cellular organization

Neurons 神经元 Cell body 胞体 Axon 轴突 Dendrites 树突

Neuroglia － glial cell 胶质细胞

Structural classification Bipolar neuron 双极神经元 has an axon and a dendrite Pseudounipolar neuron

假单极神经元 has a central branch and a peripheral branch

Multipolar neuron 多极神经元 has an axon and two or more dendrites

Functional classification Sensory (efferent) neuron

感觉神经元 Motor (afferent) neuron

运动神经元 Association neuron 联络神经元

Reflex: a reaction of the organism by the nervous system in response to a stimulus

Reflex arc: has 5 basic components Receptor

↓ Sensory neurons ↓ CNS ↓ Moter neurons ↓ Effector

Reflex and reflex arc

Basic terminology in nervous system

In the CNS Gray matter 灰质 : collection

of nerve cell bodies and their dendrites, gray color during fresh condition

Cortex 皮质 : the outermost layer of gray matter in cerebrum and cerebellum

White matter 白质 : collection of nerve fibers, white color during fresh condition

Medulla 髓质 : a central core of white matter beneath cortex of cerebrum and cerebellum

Nucleus 神经核 : a collection ( group ) of cell bodies which have the same shape and function

Fasciculus 纤维束 ( tract ): a bundle of nerve fibers which have the same origin, termination, pathway and function

Reticular formation 网状结构 : an admixture of cross-crossing fibers with larger or smaller groups of nerve cells occupying the meshes

In the PNS Ganglion 神经节 : a c

ollection of neuronal cell bodies outside the CNS

Nerve 神经 : a bundle of nerve fibers held together by connective tissue sheath

The Spinal Cord 脊髓

Position Lies in vertebral canal Continuous above with medulla

oblongata at level of foramen magnum

Ends below at lower border of L1 in adult; at birth at level of L3

External features A long cylindrical structure and sli

ghtly flattened anteroposteriorly, Conus medullaris （脊髓圆锥） Filum terminale （终丝） Cauda equina （马尾） Two enlargements

Cervical enlargement （颈膨大） : corresponds to the C4 to the T1 segments

Lumbosacral enlargement （腰骶膨大） : corresponds to the L2 to the S3 segments

Fissure and sulci Anterior median fissure 前正中裂 Posterior median sulcus 后正中沟 Anterolateral sulcus 前外侧沟－ anterior (motor) roots emerge serially Posterolateral sulcus 后外侧沟－ posterior (sensory) roots enter spina

l cord, each bear a spinal ganglion which constitutes the first cell-station of the sensory nerves

Relationship of segments

of spinal cord to vertebrae A portion of the cord that gives

rise to a pair of spinal nerve constitutes a segment.

There are 31 segments 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal

Relationship of segments of spinal cord to vertebraeSpinal segments Vertebral levels (spines)

Upper cervical region (C1~C4) = C1 ~ C4

Lower cervical and upper thoracic region (C5~T4)

— 1 = C4 ~ T3

Middle thoracic region (T5~T8) — 2 = T3 ~ T6

Lower thoracic region (T9~T12) — 3 = T6 ~ T9

Lumber segments = T10 ~ T12

Sacral and coccygeal segments = L1

Internal structures Central canal 中央管 Gray matter

Anterior horn (column) 前角（柱） Posterior horn (column) 后角（柱） Intermediate zone 中间带

Lateral horn (column) 侧角（柱） Anterior gray commissures

灰质前连合 Posterior gray commissures

灰质后连合 White matter

Anterior funiculus 前索 lateral funiculus 外侧索 Posterior funiculus 后索 Anterior white commisure

白质前连合

Posterior horn (column): Marginal layer （缘层） Substantia gelatinosa

（胶状质） Nucleus proprius

（后角固有核） Nucleus thoracicus （胸核）

in segments C8~L3

Intermediate zone Intermediaolateral nucleus

（中间外侧核） (lateral horn or column): lies in segments T1~L3, containing sympathetic preganglionic neurons

Sacral parasympathetic nucleus（骶副交感核） : lies in segments S2~S4, containing parasympathetic preganglionic neurons

Intermediomedial nucleus （中间内侧核） : for sensation of viscera

Anterior horn (column): contain motor neurons

Three kinds of neuron α-motor neuron: larger multipolar neuron,

innervates extrafusal fibers of skeletal m., producing contraction of m.

γ-motor neuron: smaller neuron, innervates intrafusal fibers regulating muscular tonus

Renshaw’s cell: negative feedback mechanism

Two groups of nuclei Medial nuclear group: present in most se

gments of spinal cord, innervating axial muscles

Lateral nuclear group: present only in cervical and lumbosacral enlargements, innervating limb muscles

Rexed’s lamina 板层

posterior horn is formed by lamina to Ⅰ Ⅵ ；

Intermediate zone corresponding to lamina Ⅶ ；

Anterior horn is composed laminae and Ⅷ Ⅸ ；

lamina is the gray mⅩatter surrounding the central canal.

Important Subdivision of Spinal Cord Gray MatterRegion Lamina Nucleus

Posterior horn Ⅰ Marginal layer

Ⅱ Substantia gelatinosa

Ⅲ, Ⅳ Nucleus proprius

Intermediate zone Ⅶ Nucleus thoracicus (C8~L3)

Ⅶ Intermediolateral nucleus (T1~L3)

Ⅶ Sacral parasympathetic nucleus (S2~S4)

Ⅶ Intermediomedial nucleus

Anterior horn Ⅸ Motor neuron

Ⅲ) White matter White matter contains three kinds of fibers: ascendi

ng, descending, and fasciculus proprius

Ascending tracts

Fasciculus gracilis （薄束）

Fasciculus cuneatus （楔束）

Posterior spinocerebellar tract（脊髓小脑后束）

Anterior spinocerebellar tract（脊髓小脑前束）

Spinothalamic tract（脊髓丘脑束）

Ascending tractsTract Site of origin Funiculus Termination Function

Fasciculus gracilis

Spinal ganglia below segment T5

Posterior Gracile nucleus

Convey proprioceptive and fine touch sensation of trunk and limbsFasciculus cune

atusSpinal ganglia above segment T4

Cuneate nucleus

Posterior spinocerebellar

Homolateral nucleus thoracicus

Lateral Cerebellum Unconscious proprioception from lower limb and lower portion of trunk

Anterior spinocerebellar

Contralateral Laminae Ⅴ~Ⅶ

Spinothalamic Laminae ,ⅠⅣ~Ⅶ

Lateral and anterior

Dorsal thalamus

Pain, temperature and simple touch sensation of trunk and limbs

Descending tracts

Lateral corticospinal tract（皮质脊髓侧束）

Anterior corticospinal tract （皮质脊髓前束）

Rubrospinal tract （红核脊髓束）

Vestibulospinal tract（前庭脊髓束）

Reticulospinal tract（网状脊髓束）

Medial longitudinal fasciculus （内侧纵束）Tectospinal tract（顶盖脊髓束）

Fasciculus proprius （固有束）

Descending tractsTract Site of origin Funiculus Termination Function

Lateral corticospinal

Cerebral cortex Lateral Laminae Ⅳ~Ⅸanterior hor

n

Voluntary movement

Anterior corticospinal

Cerebral cortex Anterior

Rubrospinal Red nucleus Lateral Laminae Ⅶ~Ⅶ

Excitatory of flexors

Vestibulospinal Homolateral vestibular nuclei

Anterior Laminae Ⅶ~Ⅷ

Excitatory of extensors

Reticulospinal Reticular formation

Anterior and lateral

Laminae Ⅶ~Ⅷ

Voluntary movement

Medial longitudinal fasciculus

Vestibular nuclei

Anterior Laminae Ⅶ~Ⅷ

Coordinate neck with eye movement

Tectospinal Superior colliculus

Anterior Laminae Ⅵ~Ⅷ

Fasciculus proprius

Spinal cord Anterior, lateral and posterior

Spinal cord Intrinsic reflex mechanism of spinal cord

Main functions of spinal cord Conduction of excitations Reflex activity