The eye Ch 52 Flashcards

Central Neurophysiology of Vision

1
Q
A
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2
Q

Visual pathway

A

Nasal halves:
Optic nerves –>cross at optic chiasm–>optic tract

Temporal retinas: Optic nerve–>optic chiasm (don’t cross)–>optic tract

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3
Q

Fibers of optic tract synapse in

A

dorsal lateral geniculate nucleus (thalmus)

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4
Q

Visual fibers pass to (4)

A
  1. suprachiasmatic nucleus of hypothalmus
  2. Pretectal nuclei in midbrain
  3. Superior colliculus
  4. Ventral lateral geniculate nucleus of thalmus
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5
Q

Suprachiasmatic nuclus of hypothalmus responsible for

A

circadian rhythms

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6
Q

Pretectal nuclei in midbrain responsible for

A

reflex movement of eye

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7
Q

Superior colliculus responsible for

A

eye movement

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8
Q

Ventral lateral geniculate nucleus of thalamus responsible for

A

body behavior

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9
Q

Layers of dorsal lateral geniculate nucleus

A

half come from one eye, half from the other

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10
Q

dorsal lateral geniculate nucleus role

A

gate transmission of signals, controls how much of signal passes to cortex

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11
Q

Magnocellular layers input comes from

A

type M ganglion cells

(rapid conduction, black and white)

Lizard brain

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12
Q

Parvocellular layers get input from

A

type P ganglion cells

(transmit color, convey accuracy, moderate conduction velocity)

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13
Q

Visual cortex location

A

calcarine fissure area, terminus of visual signals

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14
Q

Primary visual cortex has ___ layers

A

6 layers

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15
Q

M retinal ganglion cells terminate

A

in Ivcalpha

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16
Q

P ganglion cells terminate in

A

layer Iva and Ivcbeta

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17
Q

color blobs role

A

activated by color signals, thought to decipher color

18
Q

Two pathways for analysis of visual information

A
  1. 3-D position, gross forms and motion of objects
  2. Analysis of visual detail and color
19
Q

Perimetry

A

measures blindess in portions of the retina

20
Q

Scotomata

A

blind spots outside of optic disk

21
Q

Retinitis pigmentosa

A

portions of retina degenerate and lead to excessive melanin deposits

22
Q

Lesion on optic nerve yields

A

blindness

23
Q

lesion bitemporal hemainopsia

A

interruption of optic chiasm prevents crossing of impulses = half blindess

24
Q

Lesion homonyous hemianpsia

A

interruption of an optic tract results in the loss of nervet in the corressponding half of retina

same side lesion, niether eye can see objects to opposite side of head

25
Q

Neural pathway for vision

A

CN III
CN IV
CN VI

25
Q

How many eye muscles are there

A

3 pairs (6 total)

26
Q

Voluntary fixation movements

A

person chooses to find object to focus on

27
Q

involuntary fixation movements

A

holds eye firmly once it has been found

28
Q

Three types of eye movements

A
  1. Flicking
  2. Slow drift
  3. continuous tremor
29
Q

Saccadic movement of eye

A

continually moving visual scene - eye fixes on one object after another

i.e. reading, driving

30
Q

Pursuit movement

A

Eyes remain fixed on moving object

31
Q

Superior colliculi role

A

turning towards a visual disturbance

(also involves somatic and acoustic signals)

32
Q

Fusion of the visual image

A

if two images are not “in register” interference excitation signals oculomotor apparatus

33
Q

Stereopsis

A

Detects distances of visual objects up to 200 feet

34
Q

Depth perception is determined by

A

pathways activated - different ones register based on how far away object of focus is

35
Q

Strabismus

A

squint or cross eye, lack of fusion in one or more visual coordinates

fix: patch or surgery

36
Q

Accommodation clues - what triggers them?

A

changing distance of focus leads to clues for accomodation

37
Q

Accommodation - what else helps accomodation?

A

Pupillary diameter

38
Q

changing distance leads to the following clues for accomodation:

A
  1. Chromatic abberration - the eye can determine which color ray is better in focus
  2. convergence
  3. Clarity of focus in depth of fovea vs edges
  4. Degree of accommodation oscillates - visual image becomes clearer when oscillation of lens strength changes in proper direction
39
Q

Horners syndrome:

A

interruption of sympathetic nerve fibers to pupillary dilator muscle

pupil remains constricted in one ye and eyelid droops, blood vessels remain dilated