Sensory Receptor Cells (Cambridge (CIE) A Level Biology)

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