CO-ORDINATION AND CONTROL

• Hormones, secreted by special glands, are chemicals that help control and co-ordinate processes in your body.
• The nervous system uses electrical impulses to enable you to react to your surroundings and co-ordinate what you do.
• Cells called receptors detect stimuli ( changes in the environment).
• Impulses from receptors pass along sensory neurones to the brain. Impulses are sent from the brain to the effector organs along the motor neurones.

• Some responses to stimuli are automatic and rapid and are called reflex actions.
• Reflex actions run everyday bodily functions and help you to avoid danger.
• stimulus ---> receptor ---> co-ordinator ---> effector ---> response
• Reflex actions involve just three types of neurone. These are;

1. sensory neurones

2. motor neurones

3. relay neurones which simply connect a sensory neurone and a motor neurone. We find relay neurones in the CNS, often in the spinal chord.