Cranial Nerves & Related Anatomy

Vocabulary flashcards covering cranial nerves, key structures, and related clinical concepts discussed in the lecture.

Peripheral Nervous System (PNS)

All neural structures that exit the brain or spinal cord, including the 12 pairs of cranial nerves.

Cranial Nerves

Twelve paired nerves that emerge from the inferior surface of the brain; numbered I–XII with Roman numerals.

Olfactory Nerve (CN I)

Shortest cranial nerve; purely sensory for smell and powerful in triggering memory.

Optic Nerve (CN II)

Sensory nerve for vision and visual acuity; right and left nerves cross at the optic chiasm.

Optic Chiasm

X-shaped crossing of right and left optic nerves located anterior to the pituitary gland.

Oculomotor Nerve (CN III)

Motor nerve controlling 4 of the 6 extrinsic eye muscles and pupil constriction.

Trochlear Nerve (CN IV)

Motor nerve that moves the superior oblique muscle to help rotate the eye downward and laterally.

Abducens Nerve (CN VI)

Motor nerve that abducts the eye by activating the lateral rectus muscle.

Trigeminal Nerve (CN V)

Both sensory and motor; provides facial sensation and powers muscles of mastication; has three branches.

Ophthalmic Branch (V1)

Superior branch of the trigeminal nerve supplying sensation to the forehead and scalp.

Maxillary Branch (V2)

Middle branch of CN V supplying sensation to cheeks, upper lip, and maxilla.

Mandibular Branch (V3)

Inferior branch of CN V supplying sensation to jaw and motor fibers to chewing muscles.

Masseter Muscle

Primary chewing muscle bulging over the jaw when teeth are clenched; tested for CN V motor function.

Facial Nerve (CN VII)

Both sensory and motor; taste to the anterior 2⁄3 of tongue and controls muscles of facial expression.

Vestibulocochlear Nerve (CN VIII)

Sensory nerve with cochlear (hearing) and vestibular (balance) components.

Cochlea

Spiral inner-ear organ that converts sound waves into neural signals for hearing.

Vestibule & Semicircular Canals

Inner-ear structures that detect head position and movement for balance.

Vertigo

Sensation that the room is spinning, often due to inner-ear otolith disturbances affecting CN VIII.

Otoliths

Tiny calcium stones in the vestibule that shift to signal head movement; dislodgement can cause vertigo.

Glossopharyngeal Nerve (CN IX)

Both sensory and motor; taste to posterior 1⁄3 of tongue and motor to muscles of swallowing.

Deglutition

Medical term for swallowing, powered partly by CN IX.

Vagus Nerve (CN X)

Longest cranial nerve; supplies parasympathetic control to thoracic and abdominal organs; both sensory and motor.

Polyvagal Theory

Concept describing how vagus nerve activity influences emotional regulation, heart rate, and gut function.

Accessory Nerve (CN XI)

Motor nerve to sternocleidomastoid and upper trapezius muscles; tested by shoulder shrug and head rotation.

Sternocleidomastoid

Neck muscle that rotates the head; activated by CN XI.

Trapezius (Upper Fibers)

Shoulder-elevating muscle innervated by CN XI; tested with resisted shoulder shrug.

Hypoglossal Nerve (CN XII)

Motor nerve that protrudes and moves the tongue; deviation indicates weakness.

Extrinsic Eye Muscles

Six skeletal muscles that move each eyeball voluntarily (4 rectus, 2 oblique).

Superior Oblique Muscle

Eye muscle controlled by CN IV, enabling downward and lateral gaze (eye roll).

Lateral Rectus Muscle

Eye muscle controlled by CN VI, abducting the eye away from midline.