Receptors and Nervous system

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Describe a basic reflex arc?
Stimulus -> Receptor -> CNS -> Effector -> Response.
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Why are reflexes important?
To avoid damage to body tissue. To enable escape from predators. Increase chances of finding a mate, food etc.
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Three types of neurones?`
Sensory, relay and Motor.
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What is a Pacinian Corpuscle?
A mechanoreceptor - detects pressure change etc.
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How does it work?
The Pacinian corpuscle contain a sensory nerve ending. When stimulated, lamellae around the SNE are deformed, pressing against it. This deforms stretch mediated Na+ channels. Inc permeability to Na+ creating a gen potential which results in an A.P.
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Where are rods and cones located?
In the fovea (in the retina) of the eye.
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Where is the blind spot?
Where the optic nerve leaves for the brain - no photoreceptor cells.
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How is light converted into an impulse?
Light is absorbed by pigments in the photoreceptors (usually cones?) and bleaches the pigments. Causes chem change + results in increased permeability to Na+. Gen potential created and if threshold reached impulse sent along bipolar neurone to brain.
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Describe rods?
High sensitivty - many rods to one neurone, so many weak gen potentials can combine to fire an A.P. Low acuity as many to one - so cannot distinguish points. Found in periphery of eye.
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Describe cones?
Low sensitivity - single cone to neurone connection so more light/gen potentials need to trigger A.P. High acuity as cones close together and single cone-neurone connection so can distinguish between separate points - an A.P. for each cone.
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Card 2

Front

Why are reflexes important?

Back

To avoid damage to body tissue. To enable escape from predators. Increase chances of finding a mate, food etc.

Card 3

Front

Three types of neurones?`

Back

Preview of the front of card 3

Card 4

Front

What is a Pacinian Corpuscle?

Back

Preview of the front of card 4

Card 5

Front

How does it work?

Back

Preview of the front of card 5
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