The Nervous System

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The Nervous System

• ??????? ?????
• ???

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Divisions

• Central nervous system (CNS)
• Peripheral nervous system (PNS)

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• Central nervous system (CNS)
• Brain ?
• Telencephalon ??
• Diencephalon ??
• Cerebellum ??
• Brain stem ??
• Midbrain ??
• Pons ??
• Medulla oblongata ??
• Spinal cord ??

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• Peripheral nervous system (PNS)
• Cranial n. (12 pairs) ???
• Spinal n. (31 pairs) ???
• Visceral n. ????
• Visceral sensory n.
• Visceral motor n
• Sympathetic part ????
• Parasympathetic part ?????

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Cellular organization

• Neurons ???
• Cell body ??
• Axon ??
• Dendrites ??
• Neuroglia -glial cell????

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• 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
  dendrites
• Functional classification
• Sensory (efferent) neuron ?????
• Motor (afferent) neuron ?????
• Association neuron ?????

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Reflex and reflex arc

• 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

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Basic terminology in nervous system
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• 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
• Nucleus??? a collection ( group ) of cell bodies
  which have the same shape and function

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• 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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• 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 ??

• 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

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External features

• A long cylindrical structure and slightly
  flattened anteroposteriorly,
• Conus medullaris (????)
• Filum terminale (??)
• Cauda equina (??)
• Two enlargements
• Cervical enlargement (???) corresponds to
  the C4 to the T1 segments
• Lumbosacral enlargement (????)
  corresponds to the L2 to the S3 segments

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• Fissure and sulci
• Anterior median fissure ????
• Posterior median sulcus ????
• 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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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

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Relationship of segments of spinal cord to
vertebrae
Spinal segments Vertebral levels (spines)
Upper cervical region (C1C4) C1 C4
Lower cervical and upper thoracic region (C5T4) 1 C4 T3
Middle thoracic region (T5T8) 2 T3 T6
Lower thoracic region (T9T12) 3 T6 T9
Lumber segments T10 T12
Sacral and coccygeal segments L1
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Internal structures

• Central canal ???
• Gray matter
• Anterior horn (column) ??(?)
• Posterior horn (column)??(?)
• Intermediate zone ???
• Lateral horn (column) ??(?)
• Anterior gray commissures ?????
• Posterior gray commissures ?????
• White matter
• Anterior funiculus ??
• lateral funiculus ???
• Posterior funiculus ??
• Anterior white commisure ?????

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• Posterior horn (column)
• Marginal layer (??)
• Substantia gelatinosa (???)
• Nucleus proprius (?????)
• Nucleus thoracicus(??) in segments C8L3

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• Intermediate zone
• Intermediaolateral nucleus (?????)(lateral horn
  or column) lies in segments T1L3, containing
  sympathetic preganglionic neurons
• Sacral parasympathetic nucleus(?????) lies in
  segments S2S4, containing parasympathetic
  preganglionic neurons
• Intermediomedial nucleus (?????) for
  sensation of viscera

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• Anterior horn (column) contain motor neurons
• Three kinds of neuron
• a-motor neuron larger multipolar neuron,
  innervates extrafusal fibers of skeletal m.,
  producing contraction of m.
• ?-motor neuron smaller neuron, innervates
  intrafusal fibers regulating muscular tonus
• Renshaws cell negative feedback mechanism
• Two groups of nuclei
• Medial nuclear group present in most segments of
  spinal cord, innervating axial muscles
• Lateral nuclear group present only in cervical
  and lumbosacral enlargements, innervating limb
  muscles

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Rexeds lamina ??

• posterior horn is formed by lamina ? to ?
• Intermediate zone corresponding to lamina ?
• Anterior horn is composed laminae ? and ?
• lamina ? is the gray matter surrounding the
  central canal.

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Important Subdivision of Spinal Cord Gray Matter
Region Lamina Nucleus
Posterior horn ? Marginal layer
Posterior horn ? Substantia gelatinosa
Posterior horn ?, ? Nucleus proprius
Intermediate zone ? Nucleus thoracicus (C8L3)
Intermediate zone ? Intermediolateral nucleus (T1L3)
Intermediate zone ? Sacral parasympathetic nucleus (S2S4)
Intermediate zone ? Intermediomedial nucleus
Anterior horn ? Motor neuron
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?) White matter

• White matter contains three kinds of fibers
  ascending, descending, and fasciculus proprius

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Ascending tracts
Fasciculus gracilis(??)
Fasciculus cuneatus (??)
Posterior spinocerebellar tract (??????)
Anterior spinocerebellar tract (??????)
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 Convey proprioceptive and fine touch sensation of trunk and limbs
Fasciculus cuneatus Spinal ganglia above segment T4 Posterior Cuneate nucleus Convey proprioceptive and fine touch sensation of trunk and limbs
Posterior spinocerebellar Homolateral nucleus thoracicus Lateral Cerebellum Unconscious proprioception from lower limb and lower portion of trunk
Anterior spinocerebellar Contralateral Laminae ?? Lateral Cerebellum Unconscious proprioception from lower limb and lower portion of trunk
Spinothalamic Laminae ?, ?? Lateral and anterior Dorsal thalamus Pain, temperature and simple touch sensation of trunk and limbs
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Descending tracts
Fasciculus proprius (???)
Lateral corticospinal tract (??????)
Rubrospinal tract (?????)
Reticulospinal tract (?????)
Vestibulospinal tract (?????)
Medial longitudinal fasciculus (????)
Tectospinal tract (?????)
Anterior corticospinal tract (??????)
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Descending tracts
Tract Site of origin Funiculus Termination Function
Lateral corticospinal Cerebral cortex Lateral Laminae ?? anterior horn Voluntary movement
Anterior corticospinal Cerebral cortex Anterior Laminae ?? anterior horn Voluntary movement
Rubrospinal Red nucleus Lateral Laminae ?? Excitatory of flexors
Vestibulospinal Homolateral vestibular nuclei Anterior Laminae ?? Excitatory of extensors
Reticulospinal Reticular formation Anterior and lateral Laminae ?? Voluntary movement
Medial longitudinal fasciculus Vestibular nuclei Anterior Laminae ?? Coordinate neck with eye movement
Tectospinal Superior colliculus Anterior Laminae ?? Coordinate neck with eye movement
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

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