Cranial Nerves

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The cranial nerves are nerves that enervate the body directly from the brain without passing through the spinal cord. This is in contrast to the spinal nerves that pass through the spinal cord before reaching other parts of the body. Read on to learn more about the muscular system, and what it does in your body.

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Cranial Nerves

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Cranial Nerves
Cranial Nerves

There are twelve pairs of cranial nerves that can be seen on the ventral or bottom surface of the brain. They are usually referred to by numbers one through twelve, and written as Roman Numerals I through XII. The first and the second pair of cranial nerves emerge from the cerebrum. The other ten pairs emerge from parts of the brainstem.

The cranial nerves are responsible for both motor and sensory functions in the head and face. They are also responsible for parasympathetic control of the heart, lungs and visceral organs. The following table provides a brief description of each cranial nerve including its point of source and destination, and its sensory or motor nerve function.

Cranial Nerves and their Function
Cranial Nerve Sensory, Motor or Both Origin / Termination Function
I: Olfactory Sensory Olfactory Epithelium to Olfactory Cortex Afferent impulses for the sense of smell
II: Optic Sensory Retina to Visual Cortex Afferent impulses for vision
III: Oculomotor Motor Midbrain to eye muscles Performs most eye movements such as raising the eyelid, directing the eyeball, constricting the iris, and controlling lens shape
IV: Trochlear Motor Midbrain to superior oblique eye muscle Rotates and depresses eyeball
V: Trigeminal Both Face to Pons Sensory impulses from various areas of the face, and controls muscles for mastication
VI: Abducens Motor Pons to lateral rectus eye muscle Abducts the eye (i.e., rotate eye away from the midline of the body)
VII: Facial Both Pons to face Motor functions for muscles controlling facial expression and lacrimal and salivary glands; sensory function for taste (taste buds of anterior or front two-thirds of the tongue)
VIII: Vestibulocochlear Sensory Inner ear to pons Senses sound; also senses rotation and gravity (essential for balance and movement)
IX: Glossopharyngeal Both Medulla to throat Motor functions for part of the tongue and pharynx; Sensory function for taste from the posterior or back one-third of the tongue
X: Vagus Both Medulla to throat and organs Only cranial nerve that extends beyond the head and neck; motor functions voice and swallowing muscles, and parasympathetic control of the heart, lungs, and visceral organs; sensory function involved in taste
XI: Accessory Motor Medulla to neck Controls sternocleidomastoid and trapezius muscles for head and neck movement
XII: Hypoglossal Motor Medulla to tongue Motor innervation of tongue muscles for swallowing and speech

 

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