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Physio II: Exam 1 > L7: Vision II > Flashcards

L7: Vision II Flashcards

1
Q

layers of the retina

A 
photoreceptors
horizontal cells
bipolar cells
amacrine cells
ganglion cells
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2
Q

rods and cones interact w/ ______ cells via NT ?

A

bipolar cells

glutamate

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3
Q

amacrine cell NTs

A

8 or more kinds
including:
GABA, glycine, dopamine, ACH, indolamine

**note all are inhibitory

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4
Q

retinal layer - photoreceptors

A

rods and cones
transmit signals to outer plexiform layer

synapse w/ bipolar cells and horizontal cells

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5
Q

plexiform layer = ?

A

layer of synaptic connections

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6
Q

horizontal cells

A
  1. transmit signals from rods/cones to bipolar cells
  2. transmit signals to outer plexiform layer
  3. output is always inhibitory — lateral inhibition
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7
Q

bipolar cells

A
  1. transmit signals from rods/cones and horizontal cells
  2. transmit signals to inner plexiform layer
  3. synapse w/ amacrine and ganglion cells
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8
Q

amacrine cell signals

A

transmit signals to :
–directly from bipolar to ganglion cells

—w/in inner plexiform layer from axons of bipolar cells to dendrites of ganglion cells or to other amacrine cells

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9
Q

ganglion cells

A

transmit signals from retina to brain**

axons make up optic nerves**

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10
Q

axons of the optic nerve

A

only retina cells that transmit action potentials

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11
Q

interplexiform cells

A

transmit from inner plexiform to outer layer (retrograde signals)

inhibitory signals – lateral inhibition

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12
Q

foveal region

A

cone vision

3 neurons in direct pathway

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13
Q

3-neuron cone vision

A

cones
bipolar cells
ganglion cells

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14
Q

4-neuron rod vision

A

rods
bipolar cells
amacrine cells
ganglion cells

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15
Q

describe amacrine cells

A
  • -30 kinds
  • -dif type does dif things
    ex. rod conduction, continuing visual signals, offset of visual signals, dark or light vision, mvt
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16
Q

because of their various functions, amacrine cells are ?

A

interneurons

help analyze visual signals before they leave retina

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17
Q

describe ganglion cells

A

~60 rods and 2 cones per ganglion cell to optic nerve fiber

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18
Q

approaching the fovea, ____ rods and cones converge on each optic fibers, rods and cones also become more ______ .

A

fewer
slender

central fovea – only cones ~35k

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19
Q

what is the result of rods and cones sliming down

A

increases visual acuity in central retina

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20
Q

describe peripheral retina

A

–more sensitive to low light

up to 200 rods converge on a single optic fiber in periphery

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21
Q

types of ganglion cells

A

3 types

W, X, Y

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22
Q

W ganglion cells

A

40% of ganglion cells
small
transmit 8 m/sec

most excitation due to rods by way of small bipolar and amacrine cells

23
Q

W ganglion cell in periphery

A

broad fields in peripheral retina

because dendrites spread widely in inner plexiform layer

24
Q

X ganglion cells

A

55% of ganglion cells
medium size
transmit 14 m/sec

25
Q

X ganglion cell signals

A

small fields – discrete retinal locations

every x ganglion receives input from at least one cone cell

26
Q

cells probably responsible for all color vision

A

x ganglion cells

27
Q

Y ganglion cells

A

5%
large
transmit 50 m/sec and up
respond to rapid changes in visual image

28
Q

Y ganglion to CNS

A

transmit almost instantly

when a new visual event occurs anywhere in the field

but w/o great accuracy w/ respect to location

29
Q

dorsal lateral geniculate nucleus

A

receives input from optic nerve (in thalamus)

relays info from optic tract to visual cortex by optic radiation
= geniculocalcarine tract

30
Q

decussation in optic chiasm

A

50%

31
Q

layers of lateral geniculate nucleus

A

6 layers

2,3,5 = receive signals from lateral half of ipsilateral retina

1,4,6 = from medial half of opposite retina

32
Q

layers 1 and 2

A

magnocellular layer
large neurons
input almost entirely from Y ganglion

provide rapid conduction
only black and white

33
Q

layers 3 and 4

A

parvocellular layers
small/medium neurons
input from X ganglion

moderate conduction
color

34
Q

describe transmission gating

A

the lateral geniculate nucleus controls how much of the signal is allowed to pass to the cortex

35
Q

source of gating control

A

corticofugal fibers from primary visual cortex

reticular areas of mesencephalon

36
Q

describe sources of gating control

A

both sources are inhibitory
and
help highlight visual info that is allowed to pass

37
Q

the primary visual cortex is also called ?

A

striate cortex

38
Q

characteristics of primary visual cortex

A

in occipital lobe

6 distinct layers

geniculocalcarine fibers terminate in layer 5

39
Q

where do signals from macular area terminate in visual cortex?

A

signals from macular area terminate near occipital pole

40
Q

where do peripheral retina signals terminate in visual cortex?

A

term in concentric half circles anterior to the pole but still along the calcarine fissures

41
Q

layer 4 of primary visual cortex

A

organized into subdivisions

4calpha = signals from Y ganglion

4cbeta and 4a = signals from x ganglion

42
Q

the primary visual cortex is organized into several million vertical ______ of ______.

A

columns of neurons

30 - 50 micrometer diameter

~1000 neurons per column

43
Q

describe color blobs

A

special column-like areas
–located among the columns of 2ndary visual areas

receive lateral signals from adjacent visual columns

are activated specifically by color signals

44
Q

signals from the 2 separate eyes enter _______ stripes of columns in layer ___.

A

alternating stripes

layer 4

45
Q

what does the cortical area do?

A

deciphers whether the respective areas of the 2 visual images from each eye register w/ each other

46
Q

accommodation in children

A

refractive power of the lens can be voluntarily increased from 20 to 34 diopters

accommodation of 14

47
Q

accommodation in young person – relaxed state

A

no tension on capsule

lens assumes almost spherical shape

48
Q

accommodation in young person – normal eye conditions

A

suspensory lig. attached radially around lens

create tension
causes lens to remain flat

49
Q

meridional fibers

A

part of ciliary muscle

contract and release tension on lens

50
Q

circular fibers

A

part of ciliary muscle

decrease tension on lens

51
Q

_______ controls both sets of ciliary muscles

A

CN III

optic nerve

52
Q

accommodation in older person

A

lens is larger and thicker w/ age
less elastic

accommodation power decreased by 2 diopters by 50

decreased to 0 by 70

53
Q

define presbyopia

A

farsightedness
due to loss of elasticity of the lens

occurs typically in middle to old age
**need for reading glasses

Physio II: Exam 1 (9 decks)

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