Cranial Nerve Study Guide

The cranial nerve are 12 pairs of nerve that can be seen on the ventral surface of the brain and directly arise from the brain .

LIST OF CRANIAL NERVES :
CRANIAL NERVE I : OLFACTORY NERVE
CRANIAL NERVE II : OPTIC NERVE
CRANIAL NERVE III : OCCULOMOTOR NERVE
CRANIAL NERVE IV : TROCHLEAR NERVE
CRANIAL NERVE V : TRIGEMINAL NERVE
CRANIAL NERVE VI : ABDUCENS NERVE
CRANIAL NERVE VII : FACIAL NERVE
CRANIAL NERVE VIII : VESTIBULOCOCHLEAR NERVE
CRANIAL NERVE IX : GLOSSOPHARYNGEAL NERVE
CRANIAL NERVE X : VAGUS NERVE
CRANIAL NERVE XI : ACCESSORY NERVE
CRANIAL NERVE XII : HYPOGLOSSAL NERVE

OLFACTORY :
ORIGIN : olfactory mucosa
TERMINATION : olfactory bulb
TYPE : sensory nerve
FUNCTION : sense of smell
PATHWAY : Through the olfactory
This nerve fibres synapse with the mitral cells forming collection called glomeruli and from it 2nd order nerves then pass posteriorly into olfactory tract.
The olfactory tract runs inferiorly to frontal lobe and as tract reaches anterior perforated substances it divides into medial (carry axon across the medialplane of anterior commisure ) and lateral stria ( carries axon to olfactory area of cortex )
PALSY :
Anosmia is defined as absence of sense of smell .it can be temporary , permanent, progressive or congenital

OPTIC NERVE
ORIGIN : retina of
This produce visual defect affecting the peripheral vision in both eyes known as BITEMPORAL HEMIANOPIA

OCCULOMOTOR NERVE :
ORIGIN : mid brain
TERMINATION : muscles of lens of eye
TYPE : motor nerve
FUNCTION : control eye movement
PATHWAY : through the superior orbital fissure
COURSE :
The nerves leaves the mid brain between posterior cerebral and superior cerebellar arteries pierces the selar diaphragm over the hypophysis. Subsequently upon piercing the cavernous sinus ,it enters the superior orbital fissure and then forms 2 divisions :
Superior division : innervates superior rectus and levator palpebrae superioris ,sympathetic fiber runs to innervate the superior tarsal muscle.
Inferior division : innervates inferior and medial rectus and inferior oblique , parasympathetic fiber to ciliary ganglion which runs to innervate ciliary muscle.
PALSY :
Damage of occulomotor nerve is due to increasing intracranial pressure and cavernous sinus infection.
PTOSIS (dropping upper eyelid ) due to paralysis of levator palpabrae superioris
DILATED PUPIL – due to unopposed action of dilator pupilae muscle .

TROCHLEAR NERVE
ORIGIN : mid brain
TERMINATION : oblique eye