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NSB > Physiology of Vision > Flashcards

Physiology of Vision Flashcards

1
Q

Vision:

A

insert diagram

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2
Q

Optics of Vision

A
  • light travels through the layers of
    globe
  • light is refracted
  • image formed on the retina by
    phototransduction
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3
Q

Phototransduction is

A

conversion of light/photon energy into neural/electrical potential energy

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4
Q

What structures refract light rays in the globe and how?

A
  • cornea = 2/3 = convex = converge
  • lens = 1/3 = biconvex = converge

concave lens = diverge light rays
convex lays = converge light rays

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5
Q

Refractive power of a material:

A
  • higher the power, more
    convergent/divergent effect on
    rays
  • Dioptres D
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6
Q

What is the focal length?

A
  • distance from parallel light rays
  • entering material t othe point of
    convergence of light rays which is
    normally on the retina
  • different dimensions of eye would
    cause refractive error, hence not
    projecting onto the retina
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7
Q

Which of the following has the largest refractive power?

A

last lens

steeper angle

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8
Q

Which of the globe structures can change to change refraction of light?

A

Lens

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9
Q

How is the lens controlled?

What lens shown below? Effect?

A
  • ciliary bodies
  • cillary muscle contracts -> zonular
    fibers have less tension ->
    spherical lens = more focusing
    power, near focus = PARASYMP
    = closer to eye structures
  • ciliary muscle relaxes -> zonular
    fibers are more tense -> flatter
    lens, less focusing power, far focus
    = SYMP = long distance vision

Pilocarpine is a muscarinic receptor agonist
Atropine is a muscarinic receptor antagonist
Muscarinic receptors PARASYMPATHETIC activity

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10
Q

Hypermetropia/Hyperopia:

A
  • long sightedness
  • eyeball too short or too weak
    refraction
  • blurred near vision, good long
    vision
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11
Q

Myopia:

A
  • short sightedness
  • eyeball too long or too strong
    refraction
  • blurred far vision, clear near vision
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12
Q

Astigmatism:

A

imperfect curvature of cornea or lens

blurred near and far vision

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13
Q

Presbyopia:

A

loss of accomodation of eye so loss of near vision

loss in shape of lens changing for near vision; (parasymp)

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14
Q

Optics of Vision:

A

insert diagram

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15
Q

Iris Function:

A
  • controls the volume of rays
    entering the posterior segment of
    the globe
  • sphincter pupillae -> constricts
    pupil, decreases light in response
    to bright light = parasymp
  • dilator pupillae -> dilates pupil,
    increases light in response to dim
    light or fight/flight responses =
    sympathetic
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16
Q

Which layer of the eye contains the retina?

The optic part of the retina has how many layers?

What is/are the layer/s called?

A
  • internal neural layer
  • non-visual and optic
  • optic further divided into external
    pigmented layer and neural
    internal layer
  • external = absorbs excess light
    and prevents reflections of light
  • internal = neurologically
    functional layer, photosensitive
17
Q

How many cell types in the neural internal layer of the retina?

A

3 neural cell types

1) photoreceptors: rods and cones
2) bipolar neurons
3) ganglion cells

18
Q

Function of rod cells:

A

receptive to dim light
light sensitive

19
Q

Function of cone cells:

A
  • receptive to bright light
  • colour sensitive receptors
20
Q

What pigment in rods?

A

rhodopsin (light sensitivity)

21
Q

What pigments in cones?

A

photopsin (colour sensitivity)

22
Q

What are the two transverse cell types of the neural internal layer of the retina?

A
  • horizontal cells: lateral inhibition
    of bipolar cells
  • amacrine cells: contrast
    enhancement and movement
    detection
23
Q

What cell types are involved in colour vision?

A
  • cones = photoreceptors
  • L cones/photopsin I: Red
  • M cones/photopsin II: Green
  • S cones/photopsin III: Blue
24
Q

Red-Green Colour Blindness:

A

X chromosome linked
hence more common in male
only one mutated copy needed for expression

25
Q

Blue Colour Blindness:

A

chromosome 7

26
Q

Visual Fields:

A

image in the environment/external correct orientation

27
Q

Retinal Field:

A

image in inversion of the visual field
image on the retina
light travels in straight lines

28
Q

Visual and Retinal Fields:

A

insert slide

29
Q

Visual Pathway: Components:

A

optic nerve
optic chiasm
optic tract
lateral genticulate nucleus of thalamus or superior colliculus
optic radiation
primary visual cortex

30
Q

Ipsilateral Eye Blindness:

A
  • damage to the optic nerve
  • loss of sight in one eye
31
Q

Bitemporal hemianopia:

A
  • loss of vision on temporal field of
    both eyes
  • damage to the optic chiasm
32
Q

Homonymous hemianopia:

A
  • loss of vision on eg the left visual
    field of both eyes hence one
    temporal field and one nasal field
  • damage to the optic radiation
    fibers
33
Q

Each primary visual cortex will have visual information from both eyes.

Draw pathways.

A
  • nasal visual field seen on retinal
    temporal field
  • optic nerve
  • fibers pass through genticulate
    nucleus on ipsilateral side to the
    primary visual cortex

nasal visual field = ipsilateral primary visual cortex
temporal visual field = contralateral primary visual cortex

  • temporal visual field seen on
    retinal nasal field
  • optic fiber
  • crossed over at optic chiasm
  • passes through lateral genticulate
    nucleus
  • to contralateral primary visual cortex
34
Q

Defects at each number causes?

A
35
Q

Pituitary gland tumour may result in what visual defect?

A
  • grows upward
  • squashes optic chiasm
  • temporal fibers cross and are
    hence lost
  • bitemporal hemianopia
36
Q

What might cause homonymous hemianopia?

A

disturbance top optic radiations on one side

stroke, tumour, inflammation, injury

37
Q

Scotoma:

A
  • blind spot
  • spot loss of vision, unilateral,
    bilateral, temporary or permanent
38
Q

Visual Agnosia:

A

inability to recognise visually present objects despite normal visual fields, acuity and colour
vision

once visual info has gone to primar visual cortex, can project via the temporal ventral route or the parietal dorsal route

*ventral route = recognition of object

dorsal route = visually guided movements

39
Q

Prosopagnosia:

A

inability to recognise familiar faces

once visual info has gone to primar visual cortex, can project via the temporal ventral route or the parietal dorsal route

*ventral route = recognition of object

dorsal route = visually guided movements

NSB (50 decks)

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