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Introduction to the Cranial Nerves
The cranial nerves appear in pairs at the bottom surface of the brain. Their functions vary, but main functions include muscle control, helping the brain interpret the five senses, and controlling glands in the human body. Each cranial nerve pair controls specific functions of the human body.
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The 12 cranial nerves each have a name and corresponding Roman numeral.
- I is the olfactory nerve
- II is the optic nerve
- III is the oculomotor nerve
- IV is the trochlear nerve
- V is the trigeminal nerve
- VI is the abducens nerve
- VII is the facial nerve
- VIII is the vestibulocochlear nerve
- IX is the glossopharyngeal nerve
- X is the vagus nerve
- XI is the spinal accessory nerve
- XII is the hypoglossal nerve
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Each of the 12 cranial nerves has a specific function that helps the brain control the actions of the body.
- The olfactory nerve is involved in the sense of smell. This nerve has access to the cerebral cortex, but does not pass through the thalamus like other cranial nerves.
- The optic nerve is involved in the sense of sight. Responsible for vision, damage to this nerve can result in temporary or permanent blindness. Ophthalmologists use the location of visual disturbances to determine if damage to the optic nerve is present.
- The oculomotor nerve controls pupil constriction and eye movement. This nerve allows us to move our eyes in response to stimuli and dilate or constrict our pupils in response to changing light conditions.
- The trochlear nerve also plays a role in the movement of the eyes. This nerve is especially important for looking down and looking in toward a midline object.
- The trigeminal nerve plays a role in controlling the muscles needed for chewing. This nerve also provides the senses of pain and touch for the head and face.
- The abducens nerve allows the eyes to move away from the midline of the face. This nerve must work with cranial nerves III and IV for correct vision. If these nerves don’t work together, double vision occurs.
- The facial nerve controls the muscles used in smiling, frowning, and other facial expressions. It also helps produce taste in two-thirds of the tongue and allows for the sensations of touch and pain from the ear.
- The vestibulocochlear nerve has separate acoustic and vestibular divisions. The acoustic portion of the nerve allows for proper hearing. The vestibular division is essential for normal balance.
- The glossopharyngeal nerve allows for taste on the back portion of the tongue, provides the sensations of pain and touch from the tongue and tonsils, and participates in the control of muscles used during swallowing.
- The vagus nerve plays an important role in the human body. It controls the sensory and motor functions of the heart and glands. It also participates in the process of digestion.
- The spinal accessory nerve allows the trapezius muscle and sternocleidomastoid muscle to control the movements of the head.
- The hypoglossal nerve allows the tongue to move properly.