Cranial Nerves Overview

Overview

This lecture covers the 12 cranial nerves, their functions (sensory, motor, or both), anatomical routes, clinical tests, and provides a mnemonic for remembering their order and modalities.

Cranial Nerve Basics

• Cranial nerves are named with Roman numerals I-XII and have unique sensory, motor, or mixed (both) functions.
• They connect the brain to various head, neck, and some body structures, serving as the interface between the CNS and PNS.
• Clinical tests assess cranial nerve function and diagnose potential nerve damage.

The 12 Cranial Nerves: Name, Function, and Tests

• I. Olfactory — Sensory; responsible for smell; tested by identifying odors like coffee grounds.
• II. Optic — Sensory; vision; tested by reading charts, color, and peripheral vision tests.
• III. Oculomotor — Motor; moves eyes; tested by following a moving object with eyes.
• IV. Trochlear — Motor; moves eyes (different muscles); also "follow the object" test.
• V. Trigeminal — Mixed; sensory from face and motor for chewing; tested by face touch sensation and chewing movements.
• VI. Abducens — Motor; moves eyes; tested by following a moving object.
• VII. Facial — Mixed; sensory for facial expression and motor for facial muscles; tested by making faces.
• VIII. Vestibulocochlear — Sensory; hearing and balance; tested by hearing and balance assessments.
• IX. Glossopharyngeal — Mixed; sensory for taste and motor for gag reflex; tested by taste and gag response.
• X. Vagus — Mixed; motor and sensory for visceral organs (e.g., digestion, speech); tested by gag reflex and ability to speak.
• XI. Spinal Accessory — Motor; shoulder movement; tested by shrugging shoulders.
• XII. Hypoglossal — Motor; tongue movement; tested by sticking out/moving tongue.

Mnemonics for Cranial Nerves

• "On Old Olympus' Towering Tops, A Finn And German Viewed Some Hops" helps remember the order of nerve names.
• Other mnemonics discussed can assist with memorizing names and functions.

Key Terms & Definitions

• Cranial nerve — A nerve emerging directly from the brain, not the spinal cord.
• Sensory nerve — Carries information from sensory receptors to the brain.
• Motor nerve — Sends signals from the brain to muscles.
• Mixed nerve — Contains both sensory and motor fibers.
• Pons, medulla, midbrain — Brainstem regions where cranial nerves connect.
• Modality — Type of function (sensory, motor, or both).

Action Items / Next Steps

• Memorize the names, numbers, and main functions of the 12 cranial nerves.
• Practice the provided mnemonic for recalling the order of cranial nerves.
• Review clinical tests for assessing each cranial nerve.