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What is a nerve?

Definition, anatomy and function of a nerve.

Show transcript

Hey everyone! It’s Matt from Kenhub and, in this tutorial, I will quickly describe, what is a nerve? If I ask you this question right now, would you be able to give me the most accurate, encyclopedia-like information describing what a nerve is? Teachers love to ask these questions and, before you panic next time you have to answer that question, here it goes.

Nerves are an essential part of the peripheral nervous system with over 100 billion cells. Nerves are the threads that connect parts of the body to other parts particularly the brain and spinal cord. On this image, you can see all these yellow structures representing some of the main nerves you find in your body.

The nerve cells found in these cord-like structures are called neurons and are made up of a large body and many branches. They have one long extension called an axon which sends impulses. The branches, called dendrites, do the receiving. The cell membrane is made up of a fat called myelin which is a very important aspect of each nerve cell. It functions like insulation around an electrical wire and damages to the myelin sheath can slow or even stop impulse transmission.

There are two types of nerves - cranial nerves and spinal nerves. Cranial nerves connect the brain with various parts of the head, neck and trunk. There are twelve pairs of them which are all these yellow structures you see on this image. Spinal nerves branch out of the spaces between the vertebrae and the spinal cord. The motor roots emerge from the ventral root – the anterior aspect of the spinal column – and from them, the brain sends messages to the body particularly to the skeletal muscles resulting in movement.

The sensory roots come out from the dorsal root – the posterior aspect of the spinal column – and they carry sensory information from the body parts back to the brain. After leaving the spinal column, these roots join together to form a spinal nerve. These join to form nerve plexuses which combine and intertwine so that all fibers associated with a certain body part join together to form one nerve.

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