CRANIAL NERVES Olfactory Nerve (I) The olfactory nerve is responsible for your sense of smell. It sends information to your brain about smells you encounter. When you smell something pleasant, such as bread baking, the aromatic molecules dissolve at the roof of your nasal cavity, which stimulates receptors to generate nerve impulses. These nerve signals are then sent to the areas of your brain that deal with memory and smell recognition. Optic Nerve (II) The optic nerve is essential for proper vision, and both of your eyes have one. When light first enters your eye, it comes in contact with receptors in your retina, called rods, which help you see black and white images and in the dark, and cones, which are responsible for color vision. Your rods and cones receive this information and pass it along to your optic nerve. The signal continues traveling along this optic nerve pathway until it reaches the visual cortex in your brain, which processes the information and ensures you can see clearly. Oculomotor Nerve (III) The word oculomotor is comprised of two parts: oculo, which relates to the eye, and motor, which can refer to movement or muscles. The oculomotor nerve, then, helps control your eyes’ muscle movements. It provides movement for the eyeball and upper eyelid while also assisting with the eyes’ involuntary functions, including pupil contraction and automatic lens adjustments (this is what happens when your eyes automatically focus on near or far objects). Trochlear Nerve (IV) The trochlear nerve is also involved in eye movement. It controls the muscle in the eye that enables it to point downward and inward. Trigeminal Nerve (V) The trigeminal nerve is the largest cranial nerve in the human body, and it has both motor and sensory functions Abducens Nerve (VI) The abducens nerve also helps with eye movements, in particular, movements that involve your gaze moving outward. Facial Nerve (VII) Like the trigeminal nerve, the facial nerve also has motor and sensory functions. It controls: Movement of muscles that produce facial expression Facial gland movement Taste Sensation in the external ear Vestibulocochlear Nerve (VIII) The vestibulocochlear nerve actually consists of two nerves in one, the vestibular nerve and cochlear nerve. The vestibular nerve helps your body sense changes in the position of your head, and your body uses this information to help it maintain its balance. The cochlear nerve helps you with hearing and determines a sound’s frequency and magnitude. Glossopharyngeal Nerve (IX) As with other cranial nerves, the glossopharyngeal nerve has both sensory and motor functions. Its sensory function receives incoming information from the back of your mouth, including the tongue, tonsils, and throat. It is also involved with taste sensation for the back of your tongue. Its motor functions are also in the throat, as it’s what allows the muscles in your throat to shorten and widen. Vagus Nerve (X) Sensory Functions: Provides sensation to the outer ear, throat, heart, and abdominal organs Motor Functions: Gives movement to the soft palate and throat Parasympathetic Functions: Regulates heart rhythm and supplies nerves to smooth muscles in your gastrointestinal tract, lungs, and airway Doctors often use vagus nerve stimulation therapy to treat conditions such as epilepsy, depression, and anxiety. The vagus nerve is also the longest of all the cranial nerves because it begins in the medulla in the brain and extends all the way to the abdominal area. Accessory Nerve (XI) This cranial nerve, the accessory nerve, provides motor function to some of the muscles in the neck. It’s what lets you rotate, flex, and extend your neck and shoulder muscles. Hypoglossal Nerve (XII) The last of the cranial nerves is the hypoglossal nerve. It provides necessary motor functions to the tongue muscles.