Cranial Nerve Functional Components

Knowledge of the cranial nerve functional components provides the basis for a thorough neurological exam.

The 12 cranial nerves participate in a total of seven neural functions. Each of these seven functions is designated by a three letter acronym.

  • The first letter is either G (General) or S (Special).
    • General refers to primitive and/or external structures of the body.
    • Special refers to senses unique to the head (taste, olfaction, hearing, vision, and balance) and to muscles of branchial arch derivatives.
  • The second letter is either S (Somatic) or V (Visceral).
    • Somatic refers to non-visceral structures including skin, muscles, tendons, joints, retina (vision), basilar membrane (hearing), and utricle/saccula (balance).
    • Visceral refers to organs of the body cavity, smooth muscle, vessels, and glands.
  • The third letter is either A (Afferent) or E (Efferent).
    • Afferent refers to flow of neural information toward the brain (sensation)
    • Efferent refers to flow of neural information toward the periphery (motor).

The Seven Functional Components

  • GSA: General Somatic Afferent
    • Touch, temperature, and pain to non-visceral structures
  • GSE: General Somatic Efferent
    • Motor to skeletal muscle
  • GVA: General Visceral Afferent
    • Touch (distention), temperature, and pain from the viscera
  • GVE: General Visceral Efferent
    • Motor to viscera, smooth muscle, and glands
  • SSA: Special Somatic Afferent
    • Vision, hearing, and balance
  • SSE: Doesn't exist
    • None
  • SVA: Special Visceral Afferent
    • Taste and olfaction
  • SVE: Special Visceral Efferent
    • Motor to muscles derived from the branchial arches

Topic revision: r2 - 30 Oct 2018, LorenEvey
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