It responds to changes in mechanical pressure. It is specific to a single type of stimulus and produces a generator potential by acting as a transducer, converting infromation from the stimulus into a form that can be understood by the body.
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Describe the structure of the pacinian corpuscle?
The sensory neurone ending at the centre of the pacinian corpuscle has a sodium channel in its plasma membrane called the stretch-mediated sodium membrane. Their permeability to sodium changes when they change shape e.g. by stretching.
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What happens when the stretch-mediated sodium channels of the membrane are in resting state?
They are too narrow to allow sodium ions to pass along them. The neurone therefore has a resting potential.
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What happens when pressure is applied to the stretch-mediated sodium channel?
It changes shape causing an influx of sodium ions to diffuse into the neurone which changes the potential of the membrane (it becomes depolarised) thereby producing a generator potential.
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What are the two types of receptors found in the eye?
Rod cells and cone cells
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What do the receptors in the light do?
They act as transducers and convert light energy into electrical energy of a nerve impulse.
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Why do rod cells only produce images in black and white?
Because they cannot distinguish between different wavelengths of light.
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Why can rod cells respond to light of a very low intensity?
Because many rod cells share a single sensory neurone which means there is a greater chance that they will exceed the threshold value.
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What is the pigment in rod cells?
Rhodopsin.
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Why do rod cells have low visual acuity?
Because there are several rod cells connected to one sensory neurone, meaning only a single impulse will be generated and as a result you cannot distinguish between the separate sources of light.
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Why do cone cells allows us to perceive images in full colour?
Because there are 3 different types of cone cells which respond to different wavelengths of light.
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Why can cone cells only respond to light of high intensity?
Because they have their own separate bipolar cell connected to a sensory neurone.
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What is the pigment found in cone cells?
Iodopsin.
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Why do cone cells have good visual acuity?
Because they have a single bipolar cell connection and so if two adjacent cells are stimulated then two impulses are received.
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Why is the distribution of rod and cone cells on the retina un-even?
Because light is focused by the lens on the fovea which receives highest intensity of light, therefore there are lots of cone cells. Whereas at the peripherus of the retina there is low light intensity so only rod cells are found.
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Other cards in this set
Card 2
Front
What is sensory reception?
Back
The function of the sense organs.
Card 3
Front
What does the pacinian corpuscle do?
Back
Card 4
Front
Describe the structure of the pacinian corpuscle?
Back
Card 5
Front
What happens when the stretch-mediated sodium channels of the membrane are in resting state?
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