Nervous System Brain

Reflexes keep the body safe

They allow us to react to changes in our environment that could cause us harm

eg. shining a bight light in your eyes, touching a hot pan, stepping on a pin

The reflex arc is used to explain how reflexes work

It involves specialised cells called neurones

There are two synapses here - two places where nerves meet

Synapses are the gaps between neurones.

They allow electrical impulses to pass from one neurone to the next

• An electrical signal travels down the first neurone to the synapse

• It triggers a chemical (neurotransmitter) to be released

• This chemical binds to receptors on the second neurone

• It triggers an electrical signal to continue down the second neurone

• Receptors detect pain or a strong stimulus

• Signal travels along sensory neurone to closest part of the CNS

• Crosses a synapse to the relay neurone

• Crosses a synapse to a motor neurone

• Sends signal down motor neurone to move a muscle or release a hormone