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Neuroscience E4 > The Visual System > Flashcards

The Visual System Flashcards

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1
Q

a thin watery fluid found anterior to the lens, between lens and cornea. supplies nutrients

A

aqueous humor

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2
Q

thick jelly like semifluid found posterior to lens, between lens and retina. maintains shape of orbit

A

vitreous humor

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3
Q

2 parts of the outer layer of the eye

A
  1. sclera - white part of the eye

2. cornea -clear portion

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4
Q

contains blood vessels and nerves (middle layer)

A

choroid

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5
Q

pigmented portion of eye

A

iris

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6
Q

parasympathetic component of CN III

A

pupillary constriction

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7
Q

pupillary dilation

A

a descending sympathetic axonal pathway from the hypothalamus synapses on preganglionic neurons of the intermediolateral cell column (lateral horn) of T1 and T2.

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8
Q

lesions at T1 or T2 result in?

A

Horner’s syndrome (sympathetic nervous system - ptosis, and pupil constriction)

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9
Q

how is the lens suspended?

A

behind the iris by “guy ropes” called zonula fibers anchored in the ciliary body

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10
Q

explain accommodation

A

the adjustment of the shape of the lens to make it more rounded done by the ciliary body (involuntary muscles) its a process that enabled one to focus on near objects and is lost with age.

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11
Q

the light sensing part of the eye (actually an extension of the diencephalon)

A

retina

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12
Q

types of cells in the retina

A

interneurons: amacrine, bipolar, horizontal cells

they help process the neural signals of the visual system

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13
Q

photoreceptors for black white gray vision and night vision

A

rods

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14
Q

photoreceptors for color vision and high visual acuity

A

cones

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15
Q

most distal part of the light path

A

photoreceptors - passage of light through all these cell layers does not reduce visual sensitivity or acuity bc the superficial layers neither absorb nor distort light

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16
Q

cells that form the optic nerve CN II

A

retinal ganglion cells - most anterior cells in the retina

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17
Q

what happens once light strikes the rods and cones?

A

produces a graded receptor potential. the excitation is passed on to several others cells of the retina. the final layer to receive the excitation is the retinal ganglion cell layer which generates an action potential

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18
Q

where are no photoreceptor, ganglion cells or other neurons present?

A

optic disk (natural blind spot) this is where the axons of ganglion cells leave the eye to form the optic nerve

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19
Q

what area is rich in cones and has no rods?

A

fovea which is in the center of the macula lutea which is a region of the retina

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20
Q

what region provides the sharp straight ahead vision that is needed for driving and reading small print?

A

macula

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21
Q

which fibers in the retinogeniculostriate pathway decussate at the optic chiasm and which do not?

A

nasal fibers decussate and temporal fibers do not

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22
Q

what causes contralateral superior quadrantanopia?

A

lesion that began in meyers loop (go through the temporal lobe after the LGN) and terminate in the lingual gyrus

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23
Q

gyrus above and below the calcarine sulcus

A 
above = cuneus ( inferior visual field)
below = lingual (superior visual field)
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24
Q

3 ways neurons in the visual cortex are categorized

A
  1. ocular dominance columns
  2. orientations columns
  3. color blobs
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25
where does the retinotectal pathway end?
superior colliculus in the midbrain tectum
26
what pathway is important in visual attention and detection of movement
retinotectal pathway
27
the retinotectal pathway activates neurons of what motor pathway?
tectospinal pathway (head/neck movement in response to novel visual stimuli)
28
what nucleus does the retinohypothalamic pathway use?
suprachiasmatic nucleus
29
what is our bodies master clock?
suprachiasmatic nucleus of the hypothalamus
30
what pathway is involved with sympathetic pupillary dilation?
retinohypothalamic pathway
31
the response of the stimulated eye
direct light response (or reflex)
32
the response of the unstimulated eye
consensual light response (or reflex)
33
in the pupillary constriction reflex, neurons in the ____________ nucleus synapse bilaterally with neurons of the ____________ nucleus which form the parasympathetic component of CN III
1. pretectal | 2. edinger-westphal
34
what activates the pupillary constrictor muscle of the iris bilaterally in response to the light stimulus?
pre-ganglionic parasympathetic neurons pass by way of CN III to the ciliary ganglion where they synapse with post ganglionic parasympathetic neurons which then active them
35
what sympathetic chain ganglia is involved with pupillary dilation?
superior cervical ganglia which sends axons to the pupillary dilator muscle of the iris
36
what refles involves adjustments of the lens by action of the ciliary body to bring closely-placed objects into focus?
accommodation-convergence relfex
37
for near vision the lens needs to be_______ and for distance vision , the lens needs to be ___________
1. near = round | 2. distance = flattened
38
after a visual stimulus (near object) reaches the visual cortex, impulses then descend to the ___________ to activate preganglionic parasympathetic neurons of the ____________ nucleus. the preganglionic neurons synapse in the _________ ganglion and cause the smooth muscles of the _________ to round the lens for near vision.
1. superior colliculus 2. edinger-westphal nucleus 3. ciliary ganglion 4. ciliary body
39
what 2 things happen after the eyes shift from a distant object to a near one (after the lens rounds) for accommodation to occur
1. eyes converge, medial rectus muscles bilaterally contract | 2. pupils constrict which increase definition
40
what are the 4 areas the visual field is divided into?
by vertical line = temporal and nasal hemiretinas | by horizonal line = superior and inferior hemiretinas
41
where do images from the upper visual field project?
to the inferior hemiretina and ultimately the lingual gyrus (meyers loop)
42
where do images from the lower visual field project?
to the superior hemiretina ultimately the cuneus gyrus
43
images from the temporal visual field project where?
nasal hemiretina
44
nasal retinal ganglion axons cross in the optic chiasm and project to?
the contralateral lateral geniculate
45
images from the nasal visual field project where?
temporal hemiretina
46
temporal retinal ganglion axons do not cross in the optic chiasm and project to?
the ipsilateral lateral geniculate
47
a midline lesion of the optic chiasm can be cause by?
craniopharyngioma, a tumor of the pituitary gland located immediately behind the optic chiasm
48
if the optic chiasm is interrupted, the result is?
bitemporal heteronymous hemianopsia or hemianopia = tunnel vision
49
interruption of the non-decussating optic tract fibers results in?
ilsilateral nasal hemianopsia ( nasal visual field lost on one side) may be due to aneurysm of interal carotid
50
complete interruption of the optic tract, lateral geniculate body, optic radiations or visual cortex on one side due to a stroke or tumor results in?
contralateral homonymous hemianopsia (blindness in the field of vision contralateral to the lesion)
51
a lesion of the cuneus gyrus results in?
contralateral lower quadrantic anopsia because pathways from the upper temporal quadrant of the ipsilateral reina and upper nasal quadrant of the contralateral retina are interupted
52
cortical blindness may occur due to
stroke, trauma, near drowning (blood/oxygen supply is interrupted
53
what causes compression of the midbrain resulting in fixed dilated pupils, ptosis and "down and out" eye?
uncal herniation through the tentorial notch as a result of increased supratentorial intracranial pressure (compression of CNIII)
54
loss of accommodation due to aging
presbyopia - lens becomes less distensible and will not round enough to focus on near objects
55
diabetes mellitus causes blood vessels of the retina to become leaky, protein escapes into the normally clear aqueous humor making it cloudy and causing light to defract blurring vision, blindness can occur
diabetic retinopathy
56
opacity of the lens of the eye, can be normal consequence of aging
cataract
57
increased intraocular pressure due to excessive aqueous humor (due to insufficient drainage secondary to bloackage in the drainage canal)
glaucoma - excess aqueous humor pushes the lens backwards into the vitreous humor which presses against the retina. compression of the retina can optic nerve can lead to blindness
58
what can cause compression of the retina and lead to progressive blindness
hypertension
59
secondary to oxygen therapy can cause damage to the retina and blindness (premature babies most at risk)
oxygen toxicity
60
a blind spot sometimes due to a small lesion in the retina.
scotoma - sometimes accompany migraines
61
a "dancing" blind spot/bright images accompanying a migraine
scintillating photoscotoma
62
separation of the layers of the retina
detached retina
63
an age related eye disease affecting the retina responsible for sharp straight-ahead vision that is needed for driving and reading small print
macular degeneration, seen in adults 65 and older

Neuroscience E4 (4 decks)

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