Biology AQA Unit 1: Nerves and Hormones
1. The Nervous System
A stimulus is a change in your environment which you may need to react to (eg. a tiger pouncing at you). You need to constantly monitor what is going on in order for you to react if you need to.
You have 5 sensory organs which each contain receptors:
- Eyes - contain light receptors.
- Ears - contain sound receptors.
- Nose - contain smell receptors.
- Tongue - contains taste receptors: sensitive to bitter, salt, sweet, and sour, plus the taste of savoury things.
- Skin - contain touch, pressure and temperature change receptors.
They all contain different receptors. Receptors are groups of cells which are sensitive to stimulus. They change stimulus energy into electrical impulses. A stimulus can be light, sound, touch, pressure, chemical or a change in position or temperature.
The central nervous system consists of the brain and spinal cord only, it coordinates a response to changes. All the information from the sensory…