The Nervous System SHANDONG UNIVERSITY Liu Zhiyu.
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Transcript of The Nervous System SHANDONG UNIVERSITY Liu Zhiyu.
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The Nervous System
SHANDONG UNIVERSITY
Liu Zhiyu
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Organizations
Central nervous system (CNS)
Peripheral nervous system (PNS)
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Major Division of the Central Nervous System (CNS)
Brain Telencephalon
Diencephalon
Cerebellum
Brain stem
Midbrain
Pons
Medulla oblongata
Spinal cord
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Major Division of the Peripheral Nervous System (PNS)
Cranial nerves (12 pairs)
Spinal nerves (31 pairs)
Visceral nerves Visceral sensory nerve
Visceral motor nerve
Sympathetic part
Parasympathetic part
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Cellular Organization
Neuron Cell body
Axon
Dendrites
Neuroglia - glial cel
l
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Classification of Neurons
Structural classification Bipolar neuron
has an axon and a dendrite Pseudounipolar neuron
has a central branch and a peripheral branch
Multipolar neuron has an axon and two or more dendri
tes
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Classification of Neurons
Functional classification Sensory (afferent) neuron Motor (efferent) neuron Association neuron
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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 ↓ Motor neurons ↓ Effector
Reflex and Reflex Arc
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Reflex and Reflex Arc
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Basic Terminology in Nervous System
In the CNS Gray matter: collection of nerve cell
bodies and their dendrites, gray color during fresh condition
Cortex: the outermost layer of gray matter in cerebrum and cerebellum
White matter: collection of nerve fibers, white color during fresh condition
Medulla: a central core of white matter beneath cortex of cerebrum and cerebellum
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Basic Terminology in Nervous System
In the CNS Nucleus:
a collection ( group ) of cell bodies which have the same shape and function
Fasciculus ( tract ): a bundle of nerve fibers which have the same origin, termination, pathway and function
Reticular formation: an admixture of cross-crossing fibers with larger or smaller groups of nerve cells occupying the meshes
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Basic Terminology in Nervous System
In the PNS Ganglion: a collection of
neuronal cell bodies outside the CNS
Nerve: a bundle of nerve fibers held together by connective tissue sheath
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The Spinal Cord
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Position of the Spinal Cord
Lies in vertebral canal Continuous above with medulla
oblongata at level of foramen magnum
Ends below at the lower border of L1 in the adult; at birth the cord ends at level of L3
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A long cylindrical structure and slightly flattened anteroposteriorly
Two enlargements Cervical enlargement correspon
ds to the C4 to the T1 segments Lumbosacral enlargement corresponds t
o the L2 to the S3 segments
Conus medullaris Filum terminale Cauda equina
External Features of Spinal Cord
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External Features of Spinal Cord
Fissure and sulci Anterior median fissure Posterior median sulcus
Posterior median septum Anterolateral sulcus - anterior
(motor) roots emerge serially Posterolateral sulcus - posterior
(sensory) roots enter spinal cord, each bear a spinal ganglion which constitutes the first cell-station of the sensory nerves
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Segments of Spinal Cord
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
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Relationship of spinal Cord Segments to Vertebral Numbers
Spinal segments Vertebral levels (spines)
Upper cervical region (C1~C4) Lie opposite the corresponding vertebrae
Lower cervical and upper thoracic region (C5~T4)
One lower in number than corresponding vertebrae
Middle thoracic region (T5~T8) Two lower in number than corresponding vertebrae
Lower thoracic region (T9~T12) Three lower in number than corresponding vertebrae
Lumber segments T10~T12
Sacral and coccygeal segments L1
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Relationship of spinal Cord Segments to Vertebral Numbers
Spinal 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
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Structure of Spinal Cord
Gray matter White matter Central canal
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Gray Matter of Spinal Cord Anterior horn (column) Posterior horn (column) Lateral horn (column) is present in th
e thoracic and upper lumber segments of the cord (T1-L3)
Intermediate zone Anterior gray commissures Posterior gray commissures
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Gray Matter of Spinal CordPosterior horn (column): Marginal layer Substantia gelatinosa
Situated at the apex of posterior horn throughout the length of spinal cord
Concerns the sensations of pain and temperature
Nucleus proprius Situated anterior to the substantia gel
ationnosa throughout the length of spinal cord
Receives fibers that are associated with the senses
Nucleus thoracicus Situated at the base of posterior horn
and extending from segments C8~L3 Associated with proprioceptive endin
gs
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Gray Matter of Spinal Cord
Intermediate zone Intermediaolateral nucleus (later
al horn) Extents from segments T1~L3, Containing sympathetic preganglioni
c neurons Sacral parasympathetic nucleus
Extents from segments S2~S4, Containing parasympathetic pregan
glionic neurons Intermediomedial nucleus
Throughout the length of spinal cord Associated with receiving viscera aff
erent information
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Gray Matter of Spinal Cord Anterior horn (column): Two kinds of motor neurons
α-motor neuron: large multipolar neuron, innervates skeletal muscles, producing contraction of muscles
γ-motor neuron: smaller multipolar neuron, innervates intrafusal muscle fibers of neuromuscular spindles, regulating muscular tonus
Interneuron —Renshaw’s cell: negative feedback mechanism
Two groups of nuclei Medial nuclear group: present in mo
st segments of spinal cord, innervating axial muscles
Lateral nuclear group: present only in cervical and lumbosacral enlargements, innervating limb muscles
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Rexed’s lamina
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 mattⅩer surrounding the central canal.
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Important Subdivision of Spinal Cord Gray Matter
Region 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
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White Matter of Spinal Cord White matter contains three kinds of fibers: ascending, d
escending, and fasciculus proprius
Anterior funiculus
Lateral funiculus
Posterior funiculus
Anterior white commissure
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Ascending Tracts
Fasciculus gracilis
Fasciculus cuneatus
Posterior spinocerebellar tract
Anterior spinocerebellar tract
Spinothalamic tract
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Fasciculus gracilis
Fasciculus cuneatus
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Spinothalamic tract
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Ascending tracts
Tract Site of origin Funiculus Termination Function
Fasciculus gracilis
Spinal ganglia below segment T5
Posterior Gracile nucleus
Conscious proprioceptive (vibratory sense, and muscle joint sense) and fine touch sensation of trunk and limbsFasciculus cu
neatusSpinal 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 , ~Ⅰ Ⅳ Ⅶ
Lateral and anterior
Dorsal thalamus
Pain, temperature and crude touch sensation of trunk and limbs
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Descending Tracts
Lateral corticospinal tract
Anterior corticospinal tract
Rubrospinal tract
Vestibulospinal tract
Reticulospinal tract
Medial longitudinal fasciculus
Tectospinal tract
Fasciculus proprius
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Descending tractsTract Site of origin Funiculus Termination Function
Lateral corticospinal
Cerebral cortex Lateral Laminae Ⅳ~Ⅸanterior horn
Voluntary movement
Anterior corticospinal
Cerebral cortex Anterior
Rubrospinal Red nucleus Lateral Laminae Ⅴ~Ⅶ
Facilitates activity of flexor muscles
Vestibulospinal Homolateral vestibular nuclei
Anterior Laminae Ⅶ~Ⅷ
Facilitates activity of extensor muscles
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
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Main functions of spinal cord
Conduction of excitations Reflex activity