Physiology II Flashcards

1
Q

Describe the passage of light inside the retinal cells

A
  1. Photoreceptors
  2. Bipolar cells
  3. ganglion cells
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2
Q

What is the role of horizontal cells?

A

Receive input from photoreceptors and project to other photoreceptors and bipolar cells

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3
Q

What is the role of amacrine cells?

A

Receive input from bipolar cells and project to ganglion cells, bipolar cells and other amacrine cells

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4
Q

What are the four main regions of the photoreceptor cell?

A

Outer segment
Inner segment
Cell body
Synaptic terminals

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5
Q

What are the types of photoreceptor?

A

Rods and cones

Cones- short, medium, long wave

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6
Q

What causes cells to release glutamate?

A

Light causes conversion of chemicals in photopigment regions causing the cell to release glutamate

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7
Q

What is the membrane potential of vertebrate photoreceptors?

A

Depolarised -20mV

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8
Q

What happens to membrane potential in photoreceptors with light exposure?

A

Hyperpolarisation

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9
Q

What is the dark current?

A

A cGMP gated Na+ channel that is open in the dark and closes in light

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10
Q

Describe the dark current in the dark

A

PNa = PK (Na channels in the outer segment)

Vm therefore between ENa and EK

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11
Q

Describe the dark current in the light

A

PNa is reduced (outer segment channels close), PK > PNa

therefore, Vm —> EK, hyperpolarizes

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12
Q

Why are photoreceptor signals amplified?

A

so we can interpret a small change in light

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13
Q

What is the visual pigment in rods?

A

Rhodopsin- vitamin A derivative + opsin (GPCR)

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14
Q

Where is rhodopsin present?

A

membrane folds (called discs in outer segment)

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15
Q

What does light convert 11-cis-retinal to?

A

all-trans-retinal (activated form)

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16
Q

In the dark there is … glutamate

17
Q

What is visual acuity?

A

ability to distinguish two nearby points.

determined largely by photoreceptor spacing and refractive power

18
Q

When do rods/cones see?

A

rods= see in dim light

cones= see in normal daylight

19
Q

Where is the highest density of cones?

20
Q

Why do rods have such a high convergence?

A

Many rods can access one ganglion giving poor acuity but allowing you to see in the dark; the signals assimilate to one larger signals

21
Q

What allows us to see in colour?

A

differnet rods and cones for specific spectra

22
Q

What does our visual system detect?

A

local differences in light intensity- not the absolute amounts of light

23
Q

What is our visual system good at?

A

Identifying differences

24
Q

What causes amblyopia?

A

multitude of issue

No problem with optics and retina

25
What happens to the visual cortex in amblyopia?
The dominant eye will take over
26
Describe hebb's postulate
Cells that fire together, wire together
27
What are the 5 characteristics of rods and cones
Rods : Cones Achromatic : Chromatic Peripheral retina : Central retina High convergence : low convergence High light sensitivity : low light sensitivity Low visual acuity : high visual acuity