Chapter 2: Peripheral Nervous System

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  1. Peripheral Nerve (LMN)
    • Motor (efferent) fibers: originate from motor nuclei (cranial nerves) or anterior horn cells (spinal nerves)
    • Sensory (afferent) fibers: originate in cells outside brainstem or SC with sensory ganglia (cranial nerves) or dorsal root ganglia (spinal nerves) 
    • Autonomic nervous system fibers: sympathetic fibers at thoracolumbar spinal segments and parasympathetic fibers at craniosacral segments
  2. Cranial Nerves
    • 12 pairs 
    • All nerves are distributed to head and neck (except CN X - distributed to thorax and abdomen)
  3. CN I, II, and VIII
    • Pure sensory
    • Carry special senses of smell, vision, hearing, and equilibrium
  4. CN III, IV, and VI
    • Pure motor
    • Control eye movements and pupillary constriction
  5. CN XI and XII
    • Pure motor
    • Innervating SCM, trap and tongue
  6. CN V, VII, IX, and X
    • Mixed motor and sensory 
    • Involved in:
    • Chewing (V)
    • Facial expression (VII0
    • Swallowing (IX, X)
    • Vocal sounds (X)
    • Sensations from head (V, VII, IX)
    • Alimentary tract, heart, vessels, and lungs (IX, X)
    • Taste (VII, IX, X)
  7. CN III, VII, IX, and X
    • Carry parasympathetic fibers of ANS
    • Involved in control of smooth muscles of inner eye (III), salivatory and lacrimal glands (VII), parotid gland (IX), muscles of heart, lung, and bowel (X)
  8. Spinal Nerves
    • 31 pairs of spinal nerves
    • Spinal nerves divided into groups: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal)
    • Correspond to vertebral segments
    • Each has a ventral root and dorsal root
  9. Spinal Nerves: Ventral (Anterior) Root
    • Efferent (motor) fibers to:
    • Voluntary muscles (alpha motor neurons, gamma motor neurons) 
    • Viscera, glands, and smooth muscles (preganglionic ANS fibers)
  10. Spinal Nerves: Dorsal (Posterior Root)
    • Afferent (sensory) fibers from skin, joints, and muscles
    • Each dorsal root possesses a dorsal root ganglion (cell bodies of sensory neurons)
    • There is no dorsal root for C1
  11. Dermatome
    Refers to a specific segmental skin area innervated by sensory spinal axons
  12. Myotome
    Refers to the skeletal muscle innervated by motor axons in a given spinal root
  13. Motor Unit
    Consists of alpha motor neuron and the muscle fiber it innervates
  14. Nerve Roots
    • Exit from the vertebral column through the intervertebral foramina 
    • In the c-spine, numbered roots exit horizontally above the corresponding vertebral body, with C8 exiting below C7 and above T1
    • In the thoracic, lumbar, and sacral spine, roots exit below the corresponding vertebral body
    • Spinal cord ends at level of L1
    • In lumbosacral region, nerve roots descend almost vertically below the cord to form caudal equine (horse's tail)
  15. Spinal Nerve Divisions
    • Emerge from intervertebral foramen 
    • Each spinal nerve divides into large anterior ramus and small posterior ramus 
    • Each ramus contains motor and sensory fibers
  16. Anterior Rami
    • Supply muses and skin of anterolateral body wall and limbs
    • Join at root of the limbs to form nerve plexuses
  17. Cervical Plexus
    Arises from C1 through C4 nerve roots
  18. Brachial Plexus
    • Arise from C5 through T1 nerve roots
    • Split into anterior and posterior divisions
    • Redistributes fibers into 3 cords (lateral, posterior, and medial)
    • Finally branch into the peripheral nerves that supply UE
  19. Lumbar Plexus
    • Arises from T12 through L4 nerve roots
    • Nerve fibers redistributed into the peripheral nerves that supply the LE
  20. Sacral Plexus
    • Arises from L4 through S3 nerve roots
    • Nerve fibers redistributed into the peripheral nerves that supply the LE

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Author:
 dmshaw9
ID:
 297795
Filename:
 Chapter 2: Peripheral Nervous System
Updated:
2015-03-08 21:57:19
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Peripheral Nervous System
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NPTE: Chapter 2
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