Detecting and responding
Sense organs
Our sense organs detect changes in the world around us known as Something that sets off a reaction in the nervous system, for example, light, heat, sound, gravity, smell, taste, or temperature. These changes in the environment are detected by receptors in an organism. The plural is stimuli.. The sense organs contain groups of specialised cells called A cell that can detect stimuli inside or outside the body. which produce electrical impulses in response to specific stimuli.
The table shows the stimuli which cause receptor cells in the sense organs to produce impulses.
| Sense organ | Stimulus |
| Skin | Temperature, pressure and pain |
| Tongue | Chemical tastes (in food and drink) |
| Nose | Chemical smells (in the air) |
| Eye | Light |
| Ear | Sound |
| Sense organ | Skin |
|---|---|
| Stimulus | Temperature, pressure and pain |
| Sense organ | Tongue |
|---|---|
| Stimulus | Chemical tastes (in food and drink) |
| Sense organ | Nose |
|---|---|
| Stimulus | Chemical smells (in the air) |
| Sense organ | Eye |
|---|---|
| Stimulus | Light |
| Sense organ | Ear |
|---|---|
| Stimulus | Sound |
Effectors
Effectors are parts of the body, such as muscles and glands, that produce a response to a detected stimulus. For example:
- a muscle contracting to move an arm
- a muscle contracting to alter pupil diameter in the eye
- a gland releasing a Chemical messenger produced in glands and carried by the blood to specific organs in the body. into the blood
This diagram summarises how information flows from receptors to effectors in the nervous system.
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- Variation – WJEC
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- Evolution – WJEC
- Homeostasis – WJEC
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