Cranial Nerves - Nerve Center In Brain and its Function
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Cranial Nerves: The Nerve Center In The Brain

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 28 Jan 2014 - 17:00.

Various types of nerves control the functions of the tissues, muscles and organs in the human body, and their nourishment is supplied through blood vessels containing energy.

The nerve supply to the body is done through two types of nervous systems: The CNS (Central Nervous System) and the Autonomous Nervous System. While we have control over the CNS we cannot exercise any control over the autonomous nervous system.

The central nervous system consists of the brain and the spinal cord which forms the basis for nerve supply to the entire body. Traveling from and to the brain  are 12 pairs of nerves called Cranial Nerves.

The 12 pairs of cranial nerves are:

1. Olfactory nerves

2. Optic nerves

3. Occulomotor nerves

4. Trochlear nerves

5. Trigeminal nerves

6. Abducent nerves

7. Facial nerves

8. Auditory nerves

9. Glossopharyngeal nerves

10. Vagus nerves

11. Accessory nerves

12. Hypoglossal nerves

These 12 pairs of cranial nerves emerge directly from the brain’s under surface. Most of these nerves supply the head, neck, face and the shoulders. Some of the organs in the chest and abdomen including the heart, lungs and most of the digestive tract are supplied by the 10th cranial nerve, the vagus.

One nerve of each pair is meant for the corresponding side of the body and is designated with a particular task to be performed.

Some of the cranial nerves are purely motor, meaning they supply muscles for their movements. Some of them are sensory, meaning they convey sensations from the periphery to the brain. Some of them are both sensory and motor.

The function of each nerve, its origin and the conditions that occur if any of these are nonfunctional (partially or totally, like in the case of paralysis) are numerous and can go into volumes of print. Therefore, an attempt is made to describe only the salient features of each nerve.

The olfactory nerves, one each for each half of the nose is purely sensory and is responsible for the relay of sensation of smell to the brain. During severe temperatures and when the nose blocks due to respiratory disorders like cold the  power to appreciate smell is temporarilylost, unless there is serious problem with the olfactory nerves as such. Through the olfactory nerve or sensory fibres the brain receives the perception of smell.

The optic nerves are also sensory in function and each nerve, meant for each eye is responsible to transmit visual information through images. The images fall on the retina upside downand the true image is interpreted in the brain substance at the center meant for vision. The occulomotor, trochlear and the abducent nerves are responsible for the external muscles of the eyeballs that help movements of the eyes. The trigeminal nerves are both sensory and motor in its functions.  These nerves relay signals from the face and also supplythe muscles meant for the act of chewing.

The facial nerves are both sensory and motor in their functions. They transmit various tastes like sweet, sour and bitter from the respective half of the tongue. The motor fibers are respon-sible for expressions of the face.

The Auditory or vestibulo-cochlear nerves are responsible for carrying sound information and balance to the ears.

The glossopharyngeal and Hypoglossal nerves carry taste sensation from a part of the tongue. They also supply muscles responsible for the movements of the tongue.

The vagus nerves also called vagabond nerves because of their multiple actions covering a vast area in the body, are responsible to regulate heartbeat and speech, besides supplying nerves to the larger part of the digestive tract.  

The accessory nerves control some movements of the head and the muscles of the shoulders. In short, the cranial nerves, some of which carry purely sensory fibers, some purely motor fibers and still some of which carry both are responsible to control most of the vol-untary and involuntary activities of the body.

The dysfunction of any part of the body is assessed by the nerves supply to that part of the body. Treatment depends on the type and extent of the nerves involved. In some conditions like a squint eye, surgery might be helpful to address the external muscles of the eyeball involved in the disorder.

*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.