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Summary of Cranial Nerves and Functions

May 2, 2025

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Overview of Cranial Nerves

This lecture provides a brief overview and recap of the cranial nerves, summarizing the primary details about each nerve including their origin, structures they supply, types of fibers, functions, whether they are sensory, motor, or both, and their passage through the skull.

Olfactory Nerve (CN I)

  • Origin: Olfactory mucosa in the roof of the nasal cavity.
  • Structures Supplied: Nasal cavity.
  • Fibers: Special visceral afferent (SVA) fibers.
  • Function: Smell (olfaction).
  • Type: Sensory nerve.
  • Skull Passage: Olfactory foramina of the cribriform plate of the ethmoid bone.

Optic Nerve (CN II)

  • Origin: Retina (ganglion cells).
  • Structures Supplied: Photoreceptors - rods, cones, and ganglion cells in the retina.
  • Fibers: Special sensory afferent (SSA) fibers.
  • Function: Vision.
  • Type: Sensory nerve.
  • Skull Passage: Optic canal.

Oculomotor Nerve (CN III)

  • Origin: Midbrain.
  • Structures Supplied: Extraocular muscles, levator palpebrae superioris, sphincter pupillae, and ciliary muscle.
  • Fibers: General somatic efferent (GSE) and general visceral efferent (GVE) fibers.
  • Function: Eye movement, eyelid elevation, pupil constriction, lens accommodation.
  • Type: Motor nerve.
  • Skull Passage: Superior orbital fissure (within the common tendinous ring).

Trochlear Nerve (CN IV)

  • Origin: Midbrain (at the level of the inferior colliculus).
  • Structures Supplied: Superior oblique muscle.
  • Fibers: General somatic efferent (GSE) fibers.
  • Function: Eye movement (depression and lateral rotation).
  • Type: Motor nerve.
  • Skull Passage: Superior orbital fissure.

Trigeminal Nerve (CN V)

  • Origin: Pons (multiple nuclei and trigeminal ganglion).
  • Structures Supplied: Facial skin, mucous membranes, muscles of mastication, tensor tympani, and other areas.
  • Fibers: Special visceral efferent (SVE), general somatic afferent (GSA), and others.
  • Function: Sensation of touch, pain, temperature, pressure; mastication.
  • Type: Both sensory and motor.
  • Skull Passage: Superior orbital fissure (V1), foramen rotundum (V2), foramen ovale (V3).

Abducens Nerve (CN VI)

  • Origin: Pons (at the level of the facial colliculus).
  • Structures Supplied: Lateral rectus muscle.
  • Fibers: General somatic efferent (GSE) fibers.
  • Function: Eye movement (abduction/lateral rotation).
  • Type: Motor nerve.
  • Skull Passage: Superior orbital fissure (inside common tendinous ring).

Facial Nerve (CN VII)

  • Origin: Pons (multiple nuclei).
  • Structures Supplied: Muscles of facial expression, stapedius, glands (lacrimal, nasal, palatine), anterior tongue.
  • Fibers: Special visceral efferent (SVE), general visceral efferent (GVE), special visceral afferent (SVA), and general somatic afferent (GSA) fibers.
  • Function: Facial expression, secretion (tears, mucus), taste (anterior 2/3 of tongue), touch and temperature sensation from ear.
  • Type: Both sensory and motor.
  • Skull Passage: Internal acoustic meatus, stylomastoid foramen.

Vestibulocochlear Nerve (CN VIII)

  • Origin: Pons-medulla junction.
  • Structures Supplied: Inner ear (vestibule, semicircular canals, cochlea).
  • Fibers: Special sensory afferent (SSA).
  • Function: Balance (static and dynamic equilibrium), hearing.
  • Type: Primarily sensory, some motor.
  • Skull Passage: Internal acoustic meatus.

Glossopharyngeal Nerve (CN IX)

  • Origin: Medulla.
  • Structures Supplied: Stylopharyngeus muscle, posterior tongue, pharynx, tonsils, carotid body.
  • Fibers: Special visceral efferent (SVE), general visceral afferent (GVA), general somatic afferent (GSA), and others.
  • Function: Elevates pharynx, taste (posterior 1/3 of tongue), touch/pain sensation.
  • Type: Both sensory and motor.
  • Skull Passage: Jugular foramen.

Vagus Nerve (CN X)

  • Origin: Medulla.
  • Structures Supplied: Pharynx, larynx, thoracic and abdominal viscera.
  • Fibers: General visceral efferent (GVE), special visceral afferent (SVA), general somatic afferent (GSA), etc.
  • Function: Parasympathetic control of heart, lungs, digestive tract; taste from epiglottis.
  • Type: Both sensory and motor.
  • Skull Passage: Jugular foramen.

Accessory Nerve (CN XI)

  • Origin: Medulla, cervical spinal cord (C1-C5).
  • Structures Supplied: Sternocleidomastoid, trapezius.
  • Fibers: General somatic efferent (GSE).
  • Function: Head movement, shoulder elevation.
  • Type: Motor nerve.
  • Skull Passage: Jugular foramen, foramen magnum.

Hypoglossal Nerve (CN XII)

  • Origin: Medulla.
  • Structures Supplied: Intrinsic and extrinsic muscles of the tongue.
  • Fibers: General somatic efferent (GSE).
  • Function: Tongue movement (protraction, retraction, elevation, depression).
  • Type: Motor nerve.
  • Skull Passage: Hypoglossal canal.

This overview is intended to provide a high-level summary of the cranial nerves, their pathways, and their functions. For detailed study, refer to individual nerve videos/lectures.

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