Sensory Receptor Cells
- A cell that responds to a stimulus is called a receptor cell
- Receptor cells are transducers – they convert energy in one form (such as light, heat or sound) into energy in an electrical impulse within a sensory neurone
- Receptor cells are often found in sense organs (eg. light receptor cells are found in the eye)
- Some receptors, such as light receptors in the eye and chemoreceptors in the taste buds, are specialised cells that detect a specific type of stimulus and influence the electrical activity of a sensory neurone
- Other receptors, such as some kinds of touch receptors, are just the ends of the sensory neurones themselves
- When receptor cells are stimulated, they are depolarised
- If the stimulus is very weak, the cells are not sufficiently depolarised and the sensory neurone is not activated to send impulses
- If the stimulus is strong enough, the sensory neurone is activated and transmits impulses to the CNS
The sense of touch
- Through their sense of touch, humans are able to distinguish between many different sensations
- The skin can be touched using different pressures such as a light touch or a jab with a sharp object - different levels of pressure feel different
- The temperature of the surrounding air can be detected by the skin - warm and cold air feel different
- All the different sensations are detected by different types of receptors found within the skin
Pacinian corpuscles
- In any area of the skin, there are a range of different receptors present
- The number of receptors present can vary in different areas of the skin
- The fingertips have a very large number of receptors
- The backs of the fingers have a much lower number of receptors
- The different receptors have different structures and positions within the skin
- Pacinian corpuscles are a type of receptor found deep in the skin
- They are present in the skin of fingers, soles of the feet as well as in joints, tendons and ligaments.
- They respond to changes in pressure
- When these receptors are stimulated by pressure on the skin it leads to the establishment of a generator potential
