Vision - Ganglion cells

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  • Created by: Jess
  • Created on: 15-05-14 10:19
What are the three types of ganglion cells?
M type, P type and others.
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What is the difference between M type and P type?
M type - large receptive fields, detect gross features, not wavelength selective. P type - small receptive field, detect fine features, wavelength selective.
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What is different about the other types of ganglion cell?
They respond to diffuse light and initiate pupillary reflexes.
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What are the three main features of ganglion cells?
Circular receptive fields, a centre and an antagonistic surround and they process info in two parallel pathways.
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What happens when you illuminate the centre of an on-centre ganglion cell?
Very strong excitation.
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What happens when you just illuminate the surround on of on-centre ganglion cell?
Very strong inhibition and, once the illumination has stopped, very strong rebound excitation.
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What dictates ganglion cell responses?
Receptors on bipolar cells.
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What mechanism underlies activation in an on-centre bipolar cell?
Hyperpolarisation in cone cell, less glutamate release in the light, less binds to mGlu6 (GPCR), unknown 2nd messenger not activated, TRPM1 channels open, Na conductance, depolarisation in the bipolar cell.
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What mechanism underlies activation in an off-centre bipolar cell?
Hyperpolarisation in cone cell, less glutamate release, AMPA receptors (ionotropic) close, bipolar cell hyperpolarises.
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Which cells can change the polarity of the light response?
Bipolar cells.
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During what polarity do action potentials fire in the ganglion cell?
Depolarisation.
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How does activation of the surround inhibit activity of the centre in off-centre bipolar cells?
Horizontal cells act as inhibitory interneurons and when AMPA receptors are active they release GABA so Cl channels open causing hyperpolarisation and less glutamate release so they don't interact with mGluR6.
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When do rods start to cooperate with cones?
As image brightness decreases.
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What happens in modrate light conditions?
Light not enough to induce a otential to release transmitter from cone. Electrical synapse between cone and rod cell opens. Rod cells change memb potential readily in low light. Cone cell changes in membrane potential due to the cooperativity.
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What happens in near dark conditions?
Electrical synapse closes. Rod cells utilise special bipolar cells and communicate via amacrine cells. More concentrated activity in the peripheral vision.
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What is protanomaly?
Causes red green colour blindness. Red cone pigment is faulty.
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What is deuteranomaly?
Causes red green colour blindness. Green cone pigment is faulty. Most common - 5% incidence in men.
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What is tritanomaly?
Causes blue yellow colour blindness. Blue cone pigment is faulty.
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Other cards in this set

Card 2

Front

What is the difference between M type and P type?

Back

M type - large receptive fields, detect gross features, not wavelength selective. P type - small receptive field, detect fine features, wavelength selective.

Card 3

Front

What is different about the other types of ganglion cell?

Back

Preview of the front of card 3

Card 4

Front

What are the three main features of ganglion cells?

Back

Preview of the front of card 4

Card 5

Front

What happens when you illuminate the centre of an on-centre ganglion cell?

Back

Preview of the front of card 5
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