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Cranial Nerves Functional Overview

Vestibulocochlear (VIII) Nerve Functions

  • Sensory Function
    • Responsible for hearing and balance.
    • DAMAGE: Can result in symptoms like deafness, dizziness, nausea, and nystagmus.

Glossopharyngeal (IX) Nerve Functions

  • Sensory Functions
    • Involved in sensation of the tongue and pharynx, including touch, taste, pressure, and pain.
  • Motor Functions
    • Controls swallowing and gag reflex.
    • Parasympathetic Role: Salivation and regulation of blood pressure.
    • DAMAGE: May lead to impaired swallowing and loss of taste, primarily for sour flavors.

Vagus (X) Nerve Functions

  • Sensory Functions
    • Provides sensory input from the gastrointestinal tract and sensation of fullness, hunger, GI discomfort.
  • Motor Functions
    • Responsible for swallowing, gastrointestinal motility, and speech.
    • Parasympathetic Role: Slows heart rate.
    • DAMAGE: Can lead to inability to swallow, hoarse voice, or severe consequences if both vagal nerves are damaged (potentially fatal).

Accessory (XI) Nerve Functions

  • Motor Functions
    • Involved in head, neck, and shoulder movements, specifically muscles such as sternocleidomastoid and trapezius.
    • DAMAGE: Causes inability to shrug shoulders or to turn head away from the injured side.

Hypoglossal (XII) Nerve Functions

  • Motor Functions
    • Controls tongue movements crucial for swallowing and speech.
    • DAMAGE: Can lead to difficulties in speech and swallowing.
    • Bilateral Damage: Causes inability to protrude tongue.
    • Unilateral Damage: Results in deviation of the tongue toward the injury side.

Summary of Functions and Damage Effects

  • VIII - Vestibulocochlear: Hearing and balance; damage leads to deafness, dizziness.
  • IX - Glossopharyngeal: Sensation and motor in tongue/pharynx; damage can impair swallowing and taste.
  • X - Vagus: Gastrointestinal functions and heart rate; damage may cause severe swallowing issues.
  • XI - Accessory: Shoulder and neck movement; damage affects movements of these areas.
  • XII - Hypoglossal: Tongue function; damage can significantly affect swallowing and speech abilities.