Explain how a reflex arc works

A reflex action is the bodies automatic and rapid response to a stimulus which we carry out without thinking. Due to it being a rapid response it doesn't involve the brain and follows a path called the reflex arc, this is a very quick process and will usually take 0.15 seconds. Receptors, generally in the skin, detect a stimulus or a change and send impulses up a sensory neurone to the spinal cord. At the spinal cord the nerve synapses for the first time and the impulse is passed across to the relay neurone in the grey matter of the spinal cord, again it then synapses and the impulse passes from the relay neurone to the motor neurone. Finally the impulse travels down the motor neurone to the effector muscle where a response is produced.