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Veterinary Physiology > Vision > Flashcards

Vision Flashcards

1
Q

What is comprised of the fibrous tunic?

A

cornea
sclera

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2
Q

What is part of the vascular part of the eye? “uvea”

A

choroid
ciliary body
iris

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3
Q

What is the nervous tunic of the eye called?

A

retina

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4
Q

What is the blind spot of the eye called?

A

optic disc

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5
Q

What is the densest part of the retina?

A

fovea centralis

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6
Q

What 2 things comprises the retina?

A

optic disc
horizontal visual streak

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7
Q

Light is _____ as it passes through the cornea and lens

A

refracted

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8
Q

The [cornea/retina] refracts more light than the lens

A

cornea

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9
Q

What fine-tunes the image?

A

lens

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10
Q

When the lens becomes [rounder/thinner], it increases refraction for near vision

A

rounder

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11
Q

What is the accommodation of the lens?

A

refracting more or less in the lens to see near of far

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12
Q

When the lens becomes [rounder/thinner], it increases refraction for distance vision

A

thinner

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13
Q

List the layers of the retina from superficial to deep

A

pigment cell layer
photoreceptor layer
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform layer
ganglion cell layer
optic nerve layer

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14
Q

What is the pigment cell layer of the retina?

A

absorbs light
prevents light from scattering between photoreceptors
convert TRANS-retinal to CIS-retinal needed by photoreceptors

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15
Q

What is the photoreceptor layer?

A

outer portion of rods and cones that contain light-sensitive components

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16
Q

What is the outer nuclear layer?

A

cell bodies and nuclei of rods and cones

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17
Q

What is the outer plexiform layer?

A

synapses of photoreceptor cell axon terminals with dendrites of retinal interneurons (bipolar and horizontal cells)

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18
Q

What is the inner nuclear layer?

A

cell bodies of retinal interneurons
- Bipolar cells (B)
- Horizontal cells (H)
- Amacrine cells (A)

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19
Q

What is the inner plexiform layer?

A

synapses of retinal interneuron axon terminals with dendrites of ganglion cells

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20
Q

What are the output cells of the retina?

A

ganglion (G) cells

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21
Q

What is the ganglion cell layer?

A

cell bodies of ganglion cells
output cells of the retina

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22
Q

What is the optic nerve layer?

A

axons of ganglion cells traversing the inner retina on their way to the optic disc —> optic nerve

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23
Q

Where is the tapetum lucidum found?

A

choroid

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24
Q

What is the tapetum lucidum?

A

reflective layer in the choroid that increases light detection in dark conditions

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25
Q

T/F: Retinal pigment epithelium lacks melanin overlying tapetum

A

true - allows light to pass through and reflect back to stimulate photoreceptors
may decrease acuity

26
Q

[Rods/Cones] are used in scotopic vision.

A

rods

27
Q

What do the outer segment of rods contain?

A

contains photopigments specialized to absorb light

28
Q

What is rhodopsin? It has a [high/low] threshold

A

absorbs light
low

29
Q

What does rhodopsin contain in combination with opsin, a G-protein coupled receptor?

A

retinal (vitamin A derivative)

30
Q

What does the outer segment of cone cells do?

A

tapers

31
Q

Cones have ______ and _____ which have a higher threshold.

A

photopsins
lodopsins

32
Q

Many domestic animals have ____ types of cones, which are composed of ______ in combination with a different type of opsin.

A

2
retinal

33
Q

What is phototransduction?

A

light converted to electric signal
cis —> trans, changes shape of G-protein
PDE degrades cGMP
cGMP gated Na+ channels close
hyper polarize the cell and decrease glutamate release

34
Q

In the dark, rhodopsin contains [cis/trans]-retinal, but with light absorption, it causes transformation to [cis/trans]-retinal which dissociates from opsin aka a “________”

A

cis
trans
bleaching reaction

35
Q

After bleaching ____ must be rebuilt for the rod to function

A

rhodopsin

36
Q

T/F: Rods function well in bright light

A

FALSE

37
Q

What is the first order neuron for the retinal pathway?

A

bipolar cell

38
Q

List the interneurons of the retinal pathway

A

bipolar cell
amacrine cell
horizontal cell processing

39
Q

List the 2nd order neuron

A

ganglion cells

40
Q

_____ work best in dim light/dark conditions

A

Rods

41
Q

Many _____ converge on one bipolar cell

A

rods

42
Q

What is MORE likely to be activated by low levels of light due to convergence of rods

A

bipolar cells

43
Q

What is the 3rd order neuron for the pathway for conscious perception of vision?

A

lateral geniculate nucleus in thalamus
“sub-cortical”

44
Q

Where do axons for the LGN go?

A

visual cortex in occipital lon
visual association areas parietal and temporal lobes

45
Q

Each visual field represented in the [ipsilateral/contralateral] optic tract

A

contralateral

46
Q

The closer together the eyes are, the [more/less] input each eye gets from BOTH visual fields

A

more

47
Q

Horses have [more/less] decussation which allows for a greater field of vision

A

more

48
Q

Increased medial eye placement —> increased binocular vision overlap —> [increased/decreased] decussation at optic chiasm

A

decreased

49
Q

T/F: Visual input that crosses the midline before entering the eye does NOT need to cross the midline again

A

TRUE

50
Q

What is the pupillary light response? What percentage of fibers of to the midbrain protextal nucleus and so on?

A

moves to rostral colliculus —> accessory oculomotor nucleus —> ciliary ganglion —> pupillary sphincter (parasympathetic)
BYPASSES the LGN
20%

51
Q

PLR is a ______ reflex inducing [sympathetic/parasympathetic]-induced pupil constriction

A

subcortical (midbrain)
parasympathetic

52
Q

Does having a pupillary light response mean you have conscious perception of vision?

A

NO - you could be blind in one eye and still have a pupillary light response

53
Q

What is anisocoria?

A

having different sized pupils

54
Q

Trace the menace response pathway

A

retina —> optic nerve —> optic disc —> optic tract —> visual cortex (lateral geniculus and rostral colliculus) —> facial motor nucleus —> facial n. in medulla —> auriculopalpebral n.

55
Q

What does subcortical mean?

A

midbrain
doesn’t go all the way to the cortex

56
Q

What does cortical mean?

A

goes all the way to the cortex

57
Q

The menace response is a [cortical/subcortical] response pathway

A

cortical

58
Q

What is the vestibulo-ocular reflex?

A

initiates compensating eye movement to keep vision fixed when head turns

59
Q

What nerves are involved in the vestibulo-ocular reflex?

A

CN 3, 4, 6

60
Q

Where is the vestibulo-ocular reflex found?

A

medial longitudinal fasciculus

61
Q

What is the visual startle reflex?

A

rostral colliculus (tectum) in midbrain
decussates
descends cord in tectospinal tract
contraction of neck muscles to turn toward stimulus

Veterinary Physiology (26 decks)

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