Cranial Nerves: Sensory, Motor Functions & Common Damage

Cranial Nerve I (Olfactory)

Relays smell signals to the olfactory bulb; signals then go to the olfactory cortex which helps us perceive smell. Type: Sensory. Damage: Loss of sense of smell (anosmia).

Cranial Nerve II (Optic)

Transports visual signals from rods and cones to the visual cortex through the optic chiasm. Type: Sensory. Damage: Before chiasm = one eye vision loss; Middle of chiasm = half vision loss in both eyes (opposite sides); Optic tract = loss of same side visual field in both eyes.

Cranial Nerve III (Oculomotor)

Controls 4 of the 6 eye muscles: superior rectus (up and in), medial rectus (inward), inferior rectus (downward), inferior oblique (up and out). Type: Motor. Damage: Eye tilts downward and outward, leading to double vision.

Cranial Nerve IV (Trochlear)

Regulates eye movement by controlling the superior oblique muscle (moves eye down and out). Type: Motor. Damage: Eye deviates up and in, double vision, and compensatory head tilt.

Cranial Nerve V (Trigeminal)

Relays sensations (pain, touch, temperature) from the face and enables chewing. Type: Sensory and Motor. Damage: Trigeminal neuralgia (short bursts of facial pain), weakened chewing muscles.

Cranial Nerve VI (Abducens)

Controls lateral rectus muscle (moves eye outward). Originates from the pons. Type: Motor. Damage: Eyes deviate inward (loss of outward movement).

Cranial Nerve VII (Facial)

Controls facial expression and carries taste from the anterior two-thirds of the tongue. Type: Sensory and Motor. Damage: Paralysis on one side of the face, loss of taste on anterior tongue.

Cranial Nerve VIII (Vestibulocochlear)

Relays auditory information and maintains balance and head position. Type: Sensory. Damage: Hearing loss, tinnitus, balance problems.

Cranial Nerve IX (Glossopharyngeal)

Relays sensory info from the posterior one-third of the tongue and assists with swallowing. Type: Sensory and Motor. Damage: Loss of taste (posterior tongue), difficulty swallowing, bursts of pain near throat or tongue.

Cranial Nerve X (Vagus)

Receives sensory info from internal organs (neck to abdomen) and serves as the main parasympathetic nerve. Type: Sensory and Motor. Damage: Irregular heartbeat, blood pressure instability, stomach pain or digestive issues.

Cranial Nerve XI (Accessory)

Controls the trapezius and sternocleidomastoid muscles for shoulder and neck movement. Located below the medulla. Type: Motor. Damage: Weakness or paralysis in these muscles, shoulder/neck pain.

Cranial Nerve XII (Hypoglossal)

Controls tongue muscles for chewing and swallowing. Type: Motor. Damage: Tongue weakness or deviation to one side.