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  • Created by: Anon
  • Created on: 10-04-15 14:31


-There are 3 types of receptors that you need to know: Pacinian corpuscles, cone cells and rod cells

-Each receptor is specific to a single type of stimulus (eg. light, heat etc.)

-Receptors act as transducers by converting the information from the stimulus into something that can be understood by the body

-They do this by producing a generator potential, which in turn creates an action potential

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Pacinian corpuscles

-Pacinian corpuscles respond to mechanical pressure and are abundant in the soles of the feet and fingers

-Each Pacinian corpuscle contains a sensory neurone which is wrapped in layers of tissue, each layer of which is separated by a gel

-The sensory neurone in each pacinian corpuscle contains stretch-mediated sodium ion channels

-This means that their permeability to sodium ions changes when the cells change shape

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Pacinian corpuscles

-Pacinian corpuscles function like so:

1. At resting potential the stretch-mediated sodium ion channels are closed

2. When pressure is applied the Pacinian corpuscle changes its shape and membrane becomes stretched 

3. This stretching widens the sodium ion channels and sodium ions diffuse into the neurone, this produces a generator potential

4. The generator potential then produces an action potential

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Rod cells

  • Rod cells are found in the retina and are more numerous than cone cells
  • Produce images in black and white
  • Bipolar cells create a generator potential and many rod cells are attached to one bipolar cell, this means that the stimuli can be combined so the threshold value is reached much more easily
  • Rod cells have low visual acuity and cannot distinguish between different sources of light
  • Rhodopsin is broken down before a generator potential is produced, this happens in low light intensity
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Cone cells

  • Cone cells also reside in the retina and are less numerous than rod cells
  • Produce images in full colour
  • Each cone cell has its own bipolar cell, so stimuli cannot be combined, meaning that cone cells only respond to high light intensity
  • Cone cells have good visual acuity and can distinguish between different sources of light
  • Iodopsin is broken down before a generator potential is produced, this only happens in high light intensity
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