Nervous System Biology unit 1a

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The Nervous System

Sensory Neurones,
The nerve cells that carry signals as electrical impulses from the receptors
in the sense organs to the
central nervous system (CNS).

Motor Neurones
The nerve cells that carry signals to the effector muscles or glands.

Muscles and glands are known as the effectors. They respond in different ways - muscles contract in response to a nervous impulse, whereas glands secrete hormones.

The Central Nervous System - Co-ordinates a response

The CNS is where all the sense organs is sent and where reflexes and actions actions are co-ordinated.

The CNS consists of the brain and spinal cord. Neurones (nerve cells) transmit the information (as electrical impulses) very quickly to and from the CNS.

''Instructions'' from the CNS are sent to the effectors (muscles and glands) which respond accordingly.


Your brain can decide how to respond to a stimulus pretty quickly. But sometimes waiting for your brain to make a decision is just too slow. That's why you have reflexes.

Reflexes help prevent injury

Reflexes are automatic responses to certain stimuli - they can reduce the chances of being injured

If someone shines a bright light into your eye your pupils dilate automatically so less light gets into the…


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