1) I is the olfactory nerve
The olfactory nerve is a characteristic sensory nerve which serves as a smell transmitter to the brain for interpretation.
2) II is the optic nerve
The optic nerve is purely sensory in nature and is responsible for vision whereby it transits all visual signals emanating from the eye’s retina to the brain for interpretation.
3) III is the oculomotor nerve
The oculomotor nerve is a type of a motor nerve which has the function of coordinating the eyeball and eyelid movements in that it innervates the inferior oblique, inferior rectus, medial rectus, superior rectus, and the levator palpebrae superioris which jointly perform most the movements of the eye.
4) IV is the trochlear nerve
The trochlear nerve is a motor nerve which innervates the muscle called superior oblique and this helps in turning the eye laterally and downwards.
5) V is the trigeminal nerve
The trigeminal nerve is both a motor and sensory nerve which obtains sensation directly from the face and also innervates all the muscles responsible for mastication.
6) VI is the abducens nerve
The abducens nerve is mainly a motor nerve and it innervates the muscle called lateral rectus and this abducts or rather turns the eye laterally.
7) VII is the facial nerve
The facial nerve is both a motor and sensory nerve and is responsible for controlling most of the facial expressions, saliva taste as well as the emission of tears.
8) VIII is the vestibulocochlear nerve
The vestibulocochlear nerve is basically a sensory nerve which functions in sensing sounds, and equilibrium sensation.
9) IX is the glossopharyngeal nerve
The glossopharyngeal nerve is both a motor and sensory nerve and it gets taste from the back of the tongue and innervates the stylopharyngeus responsible for swallowing and parotid gland which causes salvation.
10) X is the vagus nerve
The vagus nerve is both a motor and sensory nerve and it controls the larynx responsible for speaking as well as pharynx which deals with swallowing activities.
11) XI is the spinal accessory nerve
The spinal accessory nerve is a motor nerve which controls the trapezius muscles and sternocleidomastoid to assist in the movement of the head/shoulder and also overlies the function of the vagus nerve in controlling the swallowing movements.
12) XII is the hypoglossal nerve
The hypoglossal nerve is mainly a motor nerve in nature and controls all the tongue movements through innervating the tongue and glossal muscles. This is important as it enhances bolus formation (swallowing) in addition to speech articulation.