Nervous systemEverything is under control!

Nervous systemThe human nervous system is made up of two parts:

1. Central nervous system CNS. Consists of the brain and the spinal cord.

2. Peripheral nervous system PNS. Made up of nerves extending from CNS all over the body.

There are two types of actions

Voluntary action Involuntary action

Requires thinking Takes place without thinking

slower Faster

Controlled mainly by the brain

Controlled mainly by the spinal cord

For everyday actions Usually life saving actions

Reflex arc

A closer look at the reflex arc

Sensory neurone Sensory neurones receive the

stimulus, this starts an electrical impulse at the nerve endings and travels down the axon to reach the other end of the cell.

The myelin sheath insulates the cell and helps to speed up the electrical impulse.

the electrical impulse reaches the relay neurone that is in the spinal cord.

Motor neuroneThe motor neurone has a cell body right at the beginning of the cell with dendrites radiating out of it, electrical impulse received from the relay neurone will travel down the axon to reach the motor end plate that is imbedded in a muscle. This will cause the muscle to contract.