One important component of the peripheral nervous system (PNS) are cranial nerves, which are born from the encephalon. A few of them control the muscles of the head and neck area and others carry nerve impulses from the sensory organs -like the eyes- to the brain.
The 12 pairs of cranial nerves (12 towards the left and 12 towards the right) are the following:
– Olfactory nerve (1st cranial nerve): it innervates the inside of the nose and transmits signals from the olfactory cells.
– Optic nerve (2nd cranial nerve): it innervates the retina and transmits signals from the photoreceptors, which are perceived as sight.
– Oculomotor nerve (3rd cranial nerve): it controls the movements of the eye and eyelid. It also regulates the closing of the pupil and the focus of the crystalline lens.
– Trochlear nerve (4th cranial nerve): it controls the movements of the eyeball.
– Trigeminal nerve (5th cranial nerve): it controls the muscles of mastication and transmits sensory information from the eye, teeth and facial skin (cheek and jaw).
– Abducens or abducent nerve (6th cranial nerve): it regulates the direction the eye is looking at.
– Facial nerve (7th cranial nerve): it controls the muscles n charge of facial expression and stimulates salivary and lacrimal glands.
– Vestibulocochlear nerve (8th cranial nerve): it transmits sensory signals from the inner ear. There signals are perceived as sound and help us maintain our balance.
– Glossopharyngeal nerve (9th cranial nerve): it controls salivary glands and transmits sensory signals from the tongue and pharynx.
– Vagus nerve (10th cranial nerve): it is the only cranial nerve that regulates organs from the digestive, circulatory and respiratory systems.
– Accessory nerve (11th cranial nerve): it controls the muscles that are involved in swallowing and moving our head.
– Hypoglossal nerve (12th cranial nerve): it is in charge of the movements of the tongue.
