The Vagus Nerve (Cranial Nerve X)

The vagus nerve is partially responsible for parasympathetic control of the heart, lungs, and digestive tract[1]. The parasympathetic nervous system is more commonly referred to as the “rest and digest” state of the body. This is on contrast to the sympathetic nervous system, which is responsible for the “fight or flight” state of the body[2]. The vagus nerve leaves the medulla oblongata and travels down the neck, chest, and finally the abdomen[1]. It comprises 80% to 90% of afferent nerves containing mainly sensory information about the body’s organs to the central nervous system (CNS)[3]. The vagus nerve doubles as a sensory and motor nerve.

A few responsibilities of the vagus nerve include controlling heart rate, sweating, movement of muscles in the mouth, including speech, and satiation following food consumption[3].

The Glossopharyngeal Nerve (Cranial Nerve IX)

The ninth cranial nerve is both a motor nerve, carrying afferent and efferent motor information, and a sensory nerve[1]. Afferent means it is traveling from somewhere in the body to the brain.This only motor function is to elevate the pharynx[2]. The sensory aspect of the glossopharyngeal nerve comes from the pharynx, tonsils, middle ear, and posterior third of the tongue[2]. The ninth cranial nerve is responsible for the carotid sinus reflex. Sensory fibers receive information from the carotid bodies to detect blood pressure in the sinus of the carotid[2]. If there is pressure applied to the carotid artery, then the body reacts by lowering its blood pressure[2].

The Vestibulocochlear Nerve (Cranial Nerve VIII)

The vestibulocochlear nerve is also known as the auditory vestibular nerve. It transmits sound and equilibrium (balance) information from the inner ear to the brain[1]. The eighth cranial nerve splits into the cochlear nerve and the vestibular nerve. This is a primarily sensory nerve[2]. The vestibulocochlear nerve allows us to sense sound, gravity, and body rotation[2]. If a person’s eighth cranial nerve is damaged they may experience a vertigo, hearing loss, or a false sense of movement[2].

The Facial Nerve (Cranial Nerve VII)

The seventh cranial nerve comes from the pons of the brainstem[1]. The facial nerve is responsible for facial expression and conveyance of taste sensation for the front two thirds of the tongue[1]. This is both a motor and sensory nerve[2]. Facial nerve testing can be done by showing your teeth, puffing your cheeks, wrinkling your brow, frowning, and closing your eyes tightly[2]. Essentially, this nerve controls all the funny faces you can make!

The Abducens Nerve (Cranial Nerve VI)

The sixth cranial nerve is the abducens nerve. This nerve is a somatic efferent nerve, otherwise called a motor nerve[1]. The abducens nerve is responsible for innervating the lateral rectus muscle which laterally moves the eyes[2]. The sixth cranial nerve runs a lengthy path from the pons, in the brainstem, to the eyes[2].