1. Tri-teach The nervous system

2. Responding to change Our bodies have 2 ways of responding to change: The nervous system for fast, short term responses. Hormones for slow, long term responses.

3. Hormones Hormones are chemical messengers. Glands produce and release hormones. Glands that produce hormones are found in the brain (pituitary gland), ovaries and testes. Hormones are involved in the menstrual cycle, puberty and digestion.

4. The nervous system The nervous system is faster than hormones because messages are passed as electrical signals called impulses. Changes called stimuli are picked up by receptors which tend to be found in sense organs. e.g. the eye contains lots of light receptors. What types of receptor are found in the ear, skin, nose and mouth?

5. Ears contain sound receptors Mouth and nose contain chemical receptors Skin has receptors for temperature and pressure. Eyes contain light receptors

6. Passing on the message Once the receptors have detected a stimulus, the information is sent as an electrical impulse along a special cell called a neurone. Bundles of neurones are called nerves. The impulses travel at 1-120m per second. The message is sent to the central nervous system (CNS) which is the brain and spinal cord. The neurones which pass the message to the CNS are called sensory neurones.

7. Responding to a stimulus So, the message has been passed along the sensory neurones to the CNS. Now, the CNS co-ordinates the information and sends an impulse along motor neurones to the right bit of your body- called effectors. Effectors are muscles or glands.

8. Putting it all together! Receptor --> sensory neurone → CNS → motor neurone → effector. e.g. a wasp gets in the classroom. Sound receptors in your ear detect it, the message goes across sensory neurones to the CNS which processes it (**** there's a wasp in the room!!) and sends the message across motor neurones to leg muscles (effector) to make you run away.

9. Reflex actions Reflexes are important for your survival. They control actions that need to be very fast to protect you. You don't have to think about them they are automatic. e.g. knee jerk, blinking at loud noises, pulling hand away from a flame.

10. How do reflexes work? They only involve 3 types of neurone: -sensory neurones -relay neurones -motor neurones The action bypasses the brain. Sensory neurone → relay neurone--> motor neurone You move your hand before you feel any pain!

11. How synapses work There are gaps between neurones which the electrical signal can not pass across. These junctions are called synapses. To pass the message across the gap, chemicals called neurotransmitters are released to pass the message to the next neurone.