PNS

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PNS

• Structure of Nerves
• Cranial Nerves
• Spinal Nerves
• Sensory receptors
• Motor control

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Structure Classification of Nerves
Classification Sensory, Motor, Mixed, Cranial
Spinal nerves Ganglia
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Cranial Nerves

• 12 pair of nerves
• arise from brain
• exit through foramina leading to muscles, glands
  and sense organs in head neck
• Input output ipsilateral except CN II and IV

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I Olfactory Nerve
II Optic Nerve
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III Oculomotor Nerve IV Trochlear Nerve
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V Trigeminal Nerve
VI Abducens Nerve
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VII Facial Nerve
VIII Vestibulocochlear Nerve
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IX Glossopharyngeal Nerve
X Vagus Nerve
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XI Accessory Nerve
XII Hypoglossal Nerve
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Cranial Nerve Disorders

• Trigeminal neuralgia (tic douloureux)
• recurring episodes of intense stabbing pain in
  trigeminal nerve area
• pain triggered by touch, drinking, washing face
• treatment may require cutting nerve
• Bells palsy
• disorder of facial nerve causes paralysis of
  facial muscles on one side
• may appear abruptly w/ full recovery w/in 3-5
  weeks

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Spinal Nerves
- 31 pairs of mixed nerves - connect to cord via
dorsal ventral roots and rootlets - away
from cord branch into dorsal ventral rami -
nerve plexuses - nerve damage
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Dermatomes skin segment innervated by cutaneous
sensory spinal nerve
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Sensory Receptors

• Stimulus type
• mechanoreceptor, thermoreceptors, nociceptors,
  chemoreceptors photoreceptors
• Source
• exteroceptors, interoceptors proprioceptors
• Structural complexity
• simple vs. complex

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Organization of Somatosensory System
1. Receptor level sensory receptors 2. Circuit
level ascending fiber tracts 3. Perceptual
level cerebral cortex
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Hierarchy of Motor Control