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This lesson covers the structure and function of receptors with a focus on the eye and the ear as required by the Edexcel A-Level Biology specification (9BI0), Topic 9 -- Control Systems. You need to understand how these sense organs convert stimuli into nerve impulses (transduction) and how the structures within them are adapted for their functions.
A receptor is a cell or group of cells that detects a stimulus and converts it into an electrical impulse (nerve impulse). This process is called transduction.
Receptors are classified by the type of stimulus they detect:
| Receptor Type | Stimulus | Example |
|---|---|---|
| Photoreceptors | Light | Rods and cones in the retina |
| Mechanoreceptors | Pressure, vibration, sound | Hair cells in the cochlea; Pacinian corpuscles in skin |
| Thermoreceptors | Temperature change | In the skin and hypothalamus |
| Chemoreceptors | Chemicals | Taste buds; olfactory receptors; carotid body cells |
| Nociceptors | Pain (tissue damage) | Free nerve endings in skin and organs |
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