Updated: May 27
The cranial nerves can be found on the inferior surface of the brain. They leave the brain (and brainstem) and allow the passage of action potentials from the brain to areas of the face and neck.
Spinal nerves vs. cranial nerves
Spinal nerves depart from the spinal cord and leave the spinal column at intervals between the vertebrae. Spinal nerves emerge superior to C1.
The cranial nerves exist in pairs, numbered from I - XII in order of how they leave the brain from anterior to posterior. There is cranial nerve N, a small projection (extending more anterior) alongside the Olfactory neurones and terminates in the nasal mucosa which is thought to play a role in reproductive behaviour.. Cranial nerve N is called the terminal nerve and rarely features in medical and anatomical literature. N is used as there is no Roman numeral for 0.
The cranial nerves (numbered 0-12, anterior to posterior)
CN N The Terminal Nerve (hypothesised to influence reproductive behaviour)
CN I The Olfactory Nerve (transmits the sensory input for smell)
CN II The Optic Nerve (transmits the sensory input for sight, signals from the retina/fovea)
CN III The Occular Motor Nerve (motor neuron transmitting signals to the muscles of the orbit & eyelids)
CN IV The Trochlear Nerve (motor nerve that controls only the superior oblique muscle, a muscle posterior to the eye originating at the medial-superior aspect and causes abduction of the eye)
CN V The Trigeminal Nerve (facial sensation and movement of the mandible)
CN VI The Abducens Nerve (stimulates the Lactus Rectus muscle, a lateral muscle in the eye responsible for the lateral movement of the eyeball)
CN VII The Facial Nerve (stimulates muscles involved with facial expressions and has a sensory function in relaying taste stimulus from the anterior two-thirds of the tongue)
CN VIII The Vestibularcochlear Nerve (transmits sensory information from the ear allowing the brain to hear and understand balance)
CN IX The Glossopharyngeal Nerve (a highly branched neurone that allows innervation of muscles of the pharynx and salivary glands (Parotid gland) as well as transmits sensory information from the Carotid body, posterior third of the tongue and parts of the tympanic membrane (eardrum))
CN X The Vagus Nerve (large autonomic nerve allowing parasympathetic innervation of the heart, lungs and GI tract)
CN XI The Accessory Nerve (innovates the trapezius and sternocleidomastoid muscles in the lateral and posterior aspect of the neck attaching to the posterior inferior surface of the skill by tendons to the occipital and temporal bones, these allow flexion and rotation of the head)
CN XII The Hypoglossal Nerve (innovates the intrinsic and extrinsic muscles of the tongue)