Overview
This lecture covers the 12 pairs of cranial nerves, their names, functions, numbering, and pathways, including tips and mnemonics for studying them.
Cranial Nerves Basics
- Cranial nerves are part of the peripheral nervous system, carrying information to and from the brain.
- There are 12 pairs of cranial nerves, numbered using Roman numerals I–XII.
- Cranial nerves should not be confused with the 31 pairs of spinal nerves.
- Cranial nerves are named and numbered based on their function and location.
Names, Functions, and Pathways of Cranial Nerves
- I Olfactory: Sensory for smell; origin in olfactory epithelium, destination is temporal lobe.
- II Optic: Sensory for vision; origin in retina, destination is occipital lobe; crosses at optic chiasm.
- III Oculomotor: Motor for most eye muscles and intrinsic eye movements (pupil/lens).
- IV Trochlear: Motor for superior oblique eye muscle (moves eye diagonally).
- V Trigeminal: Mixed nerve with three branches (ophthalmic, maxillary, mandibular) for facial sensation and chewing.
- VI Abducens: Motor for lateral rectus eye muscle (moves eye outward).
- VII Facial: Mixed nerve for facial expression muscles, salivary/lacrimal glands, and taste from tongue.
- VIII Vestibulocochlear: Sensory for hearing and balance (inner ear).
- IX Glossopharyngeal: Mixed for taste, swallowing, and throat.
- X Vagus: Mixed nerve; controls autonomic functions of thoracic and abdominal organs.
- XI Accessory: Motor for muscles of head and neck.
- XII Hypoglossal: Motor for tongue movements.
Sensory, Motor, or Both
- Some cranial nerves are purely sensory, some motor, and some are mixed.
- Knowing the function helps determine if a nerve is sensory, motor, or both.
Origin, Destination, and Skull Exits
- Origin and destination align with nerve function (e.g., olfactory from nasal cavity to temporal lobe).
- Nerves exit or enter the brain through specific skull holes (foramina), such as the cribriform plate for olfactory and optic canal for optic.
Study Tips and Mnemonics
- Mnemonic devices help remember nerve names: "Oh, Oh, Oh, To Touch And Feel Very Green Vegetables, AH!"
- Mnemonics exist for identifying if nerves are sensory, motor, or both: "Some Say Marry Money, But My Brother Says Big Brains Matter More."
- Use diagrams and additional resources for location and pathways.
Key Terms & Definitions
- Peripheral nervous system — nerves outside the brain and spinal cord.
- Foramen — hole in the skull through which nerves pass.
- Mixed nerve — nerve carrying both motor and sensory information.
- Olfactory epithelium — sensory region in nasal cavity for smell.
- Optic chiasm — crossing point of optic nerves.
Action Items / Next Steps
- Memorize the names, numbers (Roman numerals), and functions of the 12 cranial nerves.
- Learn the skull exit points for each cranial nerve.
- Practice using mnemonics for recall.
- Review diagrams and practice identifying nerves in lab.