The nervous system is the body's wiring, a network that

stretches from our brain all the way to our toes.

The nervous system is divided into three parts.

The central nervous system includes the brain and the

spinal cord.

The spinal cord is a bundle of nerve cells starting at

the base of the brain.

And it's protected by the vertebras of your back bone.

The next part is the peripheral nervous system.

There are 31 pairs of nerves coming out between the

vertebra into the body.

They branch out throughout the whole body.

All your sensory organs, your eyes, ears, nose, skin, and

tongue all feed information to the brain through the

peripheral nervous system.

And the third part is the autonomic nervous system.

This system deals with the involuntary actions of our

body.

Things like breathing, your heart beating, or even

digesting food.

 It's called the autonomic or involuntary system because you

don't have to think about it, your brain and nerves just keep

your body functioning.

 The nervous system is made up of more than 100 billion

nerve cells.

Each cell has three main parts.

The cell body or nucleus.

Dendrites, long thin branches that grow out of the cell body.

And axons, slightly longer than thicker branches that

also come out of the cell body.

A message or impulse moves between cells.

This electrical charge travels into cell body via the

dendrites and out of the cell body through the axons.

Nerve cells are separated by tiny gaps called synapses.

When an electrical impulse reaches the synapses, the

cells release a chemical known as neurotransmitter.

The message jumps or flows across the gap with the

neurotransmitter to special landing sites known as

receptors.

 Just like a relay race.

Nerve cells pass impulses from one cell to the next.

 And nerve cells are really fast.

It only takes about one-thousandth of a second for a

message to jump from cell to cell.

 While your brain generally controls a lot of what's going

on in your nervous system, it doesn't control the body's

every movement.

If you touch something hot, the sensory nerve cells send

a signal to the muscles to tell them to move.

 Ouch!

 That automatic movement is called a reflex reaction.

Different nerve cells do different things in your body.

Some detect changes in light so you blink.

Or smells so you sniff.

Or taste so you lick.

Or sound so you hear.

Or temperatures so you sweat.

Or pressure so you move.

 You have more than a million stretch sensors in our joints,

muscles, skin and nerves to constantly monitor your body

position.

Your nervous system never rests.

And unlike other cells, the body's nerves rarely get

repaired or renewed if damaged.