The Nervous System

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The Nervous System

• ??????? ?????
• ???

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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 cell????

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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 dendrites

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Classification of Neurons

• Functional classification
• Sensory (afferent) neuron ?????
• Motor (efferent) 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
• ?
• Motor neurons
• ?
• Effector

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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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External Features of Spinal Cord

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

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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 (C1C4) Lie opposite the corresponding vertebrae
Lower cervical and upper thoracic region (C5T4) One lower in number than corresponding vertebrae
Middle thoracic region (T5T8) Two lower in number than corresponding vertebrae
Lower thoracic region (T9T12) Three lower in number than corresponding vertebrae
Lumber segments T10T12
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 (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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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 the 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 Cord

• Posterior 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 gelationnosa
  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 C8L3
• Associated with proprioceptive endings

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Gray Matter of Spinal Cord

• Intermediate zone
• Intermediaolateral nucleus ?????
  (lateral horn)
• Extents from segments T1L3,
• Containing sympathetic preganglionic neurons
• Sacral parasympathetic nucleus ?????
• Extents from segments S2S4,
• Containing parasympathetic preganglionic neurons
• Intermediomedial nucleus ?????
• Throughout the length of spinal cord
• Associated with receiving viscera afferent
  information

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Gray Matter of Spinal Cord

• Anterior horn (column)
• Two kinds of motor neurons
• a-motor neuron large multipolar neuron,
  innervates skeletal muscles, producing
  contraction of muscles
• ?-motor neuron smaller multipolar neuron,
  innervates intrafusal muscle fibers of
  neuromuscular spindles, regulating muscular tonus
• Interneuron 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 of Spinal Cord

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

Posterior funiculus??
Lateral funiculus ???

Anterior white commissure?????
Anterior funiculus ??
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Ascending Tracts
Fasciculus gracilis(??)
Fasciculus cuneatus (??)
Posterior spinocerebellar tract (??????)
Anterior spinocerebellar tract (??????)
Spinothalamic tract (?????)
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Fasciculus cuneatus
Fasciculus gracilis
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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 limbs
Fasciculus cuneatus Spinal ganglia above segment T4 Posterior Cuneate nucleus Conscious proprioceptive (vibratory sense, and muscle joint sense) 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 crude touch sensation of trunk and limbs
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Descending Tracts
Lateral corticospinal tract (??????)
Fasciculus proprius (???)
Rubrospinal tract (?????)
Medial longitudinal fasciculus (????)
Reticulospinal tract (?????)
Vestibulospinal tract(?????)
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 ?? Facilitates activity of flexor muscles
Vestibulospinal Homolateral vestibular nuclei Anterior Laminae ?? Facilitates activity of extensor muscles
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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