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Neurophysio > Retinal Physiology > Flashcards

Retinal Physiology Flashcards

1
Q

what do photoreceptors do in transduction?

A

photoreceptors convert light into a neuroelectrical response (act as a transducer)

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2
Q

what does a photoreceptor do when it is excited?

A

hyperpolarize

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3
Q

unlike typical neural cells, photoreceptors do not produce:

A

action potentials

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4
Q

for transduction, what occurs in the dark?

A

the Na+ channels are open and Na+ flows into the outer segment and is pumped out of the inner segment (continuous cycle)

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5
Q

what is the result of light on the transduction process?

A

Na+ channels close so Na+ doesn’t flow in but it is still pumped out (hyperpolarizes)

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6
Q

what is the type of neurotransmitter release that occurs in dark current transduction

A

photoreceptors release neurotransmitters continually in the dark

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7
Q

in the dark, the inside of the photoreceptor is about _____ more ____ than the outside

A

20mV more negative

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8
Q

when light hits the photoreceptor there is a series of chemical reactions that results in the inside of the cell becoming more ____, about ___ mV

A

more negative, about -60 mV

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9
Q

effects of light: rhodopsin will be converted to ->

A

opsin + all-trans retinal

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10
Q

effects of light: concentration of free cGMP _____

A

decreases

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11
Q

effects of light: decreasing the cGMP concentration results in ____ of Na+ channels

A

closes some of the

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12
Q

what is cGMP needed for?

A

needed to bind at Na+ channels to keep them open

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13
Q

effects of light: results in the inside of the cell becoming more ____ (+ or -)

A

negative

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14
Q

what retinal cells are capable of action potentials?

A

amacrine cells and ganglion cells

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15
Q

what cells are only capable of producing membrane potential changes (but NOT action potentials)?

A

photoreceptors, horizontal cells, bipolar cells

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16
Q

___ pathway causes photoreceptors to hypoerpolarize in response to light

A

ON

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17
Q

ON ganglion cell synapse is in:

A

IPL sublamina B

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18
Q

OFF ganglion cell synapse is in:

A

IPL sublamina A

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19
Q

horizontal cells can ____ adjacent bipolar cells

A

inhibit

20
Q

what is the pathway for lateral information flow? (lateral inhibition)

A

light stimulates a single photoreceptor -> stimulates bipolar cell -> stimulates ganglion cell (ON pathway)

21
Q

what are the three types of ganglion cells based on receptive field properties (cat)?

A
  • X cells
  • Y cells
  • W cells
22
Q

what ganglion cell type (cat): beta cells and responds as long as light is on?

A

X cells

23
Q

what ganglion cell type (cat): alpha cells and responds when light is turned on or off?

A

Y cells

24
Q

what ganglion cell type (cat): gamma cells?

A

W cells

25
Q

X and Y cells make up ___% of the cells and project to ____

A

80%, project to LGN

26
Q

W cells make up ___% of the cells and project to the ____

A

20%, project to the superior colliculus

27
Q

___ cells show linear spatial summation

A

X cells

28
Q

___ cells show nonlinear spatial summation

A

Y cells

29
Q

__ cells demonstrate a null point with counterpoising gratings

A

X cells

30
Q

__ cells demonstrate a doubling of their responses

A

Y cells

31
Q

in the sine wave grating, what is the most sensitive area?

A

the peak- midrange about 3-5 cycles/degree

32
Q

20/20 on a snellen chart is about ___ cycles/degree on contrast sensitivity function

A

30

33
Q

how are receptive field center and eccentricity related?

A

an increase in the receptive field center as the eccentricity is increased

34
Q

function of X cells

A

involved with pattern and spatial vision

detection of very fine, small objects

35
Q

function of Y cells

A

involved in movement or temporal vision

36
Q

types of ganglion cells found in the primates

A

P alpha (P cells) and P beta (M cells)

37
Q

P cells (P alpha cells) project to ____ layers of LGN

A

parvocellular

38
Q

M cells (P beta cells) project to the ____ layers of LGN

A

magnocellular

39
Q

P cells are ___% of the ganglion cells

A

80%

40
Q

___ cells are wavelength specific (color sensitive)

A

P cells

P beta

41
Q

spatial summation type of P cells (P beta)

A

linear

42
Q

P cells are similar to ___ cells

A

X cells

43
Q

___ cells (P/M) have large cell body

A

M cells

44
Q

M cells make up ___ % of the ganglion cells

A

10%

45
Q

are M cells wavelength specific?

A

no

46
Q

spatial summation for M cells is

A

both linear and nonlinear

47
Q

how many layers in the LGN?

A

6

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