14.4 Receptors

Definitions and explanations of receptors in the eye and the pacinian corpuscle. This is based around the AQA 2016 specification. 

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How is the resting potential maintained in a pacinian corpuscle?
The membrane is more permeable to potassium ions than sodium ions.
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Can the ear detect smell, and if not why not?
No, because receptors are specific to a certain form of stimulus
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What stimulus does the pacinian corpuscle respond to?
Mechanical pressure
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What affect does applying pressure to the pacinian corpuscle have?
1. Deforms the stretch mediated sodium channel 2. Causes channels to open and allow sodium ions enter 3. pressure gradient causes this, as less sodium ions inside than outside the membrane.
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Why do rod cells work under low light intensities?
There are many rod cells linked to one neurone, the amount of light in each separate rod cell detected summates at the neurone. This means there is a higher chance the threshold will be exceeded, so higher chance of action potential.
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Why do cone cells have a high visual acuity?
No retinal convergence as each cone has it's own neurone
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Do rod cells or cone cells distinguish between colour?
Cone cells
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What does visual acuity mean?
How clearly the image is formed
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What is retinal convergence?
The sharing of a single neurone by a number of cone cells it creates lower visual acuity
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Why does retinal convergence create low visual acuity?
Because the direction the light is coming from is less specific, as the neurone gets information from a number of cells, coming from different directions, which creates only one nerve that cannot distinguish between the directions.
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What's the definition of summation?
It's the adding up of light received from a number of cone cells
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What does action potential mean?
It's when a neurone gains enough energy to depolarise and create an impulse that gets sent to the brain
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What's a neurone?
A specialised cell that creates nerve impulses
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Where are high concentrations of cone cells found
The fovea of the retina
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How do cone cells detect light
Three types of cone cell, each specific to a different wavelength of light, which corresponds to the colours blue, red and yellow
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How do cone cells each have a specific wavelength of light that they can detect
They each have different photopsins which react to different wavelengths of light
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What's a generator potential?
Depolarisation of a receptor in response to a stimulus, results in an action potential if the threshold has been met
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What are the names of the photosensitive pigments?
Rhodopsin and Iodopsin
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When the pigments are bleached which one regenerates faster?
Rhodopsin generates slowly, iodopsin regenerates fast
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What occurs when the pigments are stimulated?
They change shape and transmit a substance to the bipolar cells
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What's the purpose of a transducer?
They convert energy received from stimuluses into a form that can be understood by the body
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What acts as a transducer?
The pacinian corpuscle
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Where are pacinian corpuscle's largely found?
Finger tips, soles of feet and external genetalia. Many also found in ligaments and tendons so organisms know when they are changing direction
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Other cards in this set

Card 2

Front

Can the ear detect smell, and if not why not?

Back

No, because receptors are specific to a certain form of stimulus

Card 3

Front

What stimulus does the pacinian corpuscle respond to?

Back

Preview of the front of card 3

Card 4

Front

What affect does applying pressure to the pacinian corpuscle have?

Back

Preview of the front of card 4

Card 5

Front

Why do rod cells work under low light intensities?

Back

Preview of the front of card 5
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