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BECOM II Exam 5 > visual system I&II - Raj > Flashcards

visual system I&II - Raj Flashcards

1
Q

retina

A

encodes visual info. to optic nerve to travel to brain

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2
Q

optic nerve

A

hemidecussation at optic chiasm to project to lateral geniculate nucleus of thalamus

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3
Q

thalamocortical neurons

A

take info. from lateral geniculate nucleus to primary visual cortex

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4
Q

where do optic nerve and retina come from?

A

prosencephalic primary brain vesicle

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5
Q

internal refractive media

A

bend light rays as they pass through the photoreceptors

-refracted before reaching retina

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6
Q

fibrous (outer) layer of eye

A

consists of sclera and cornea

  • sclera - maintains shape, attach external ocular muscles
  • cornea - translucent, avascular
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7
Q

middle (vascular) layer of the eye

A

contains choroid or uvea

  • focus light and regulate intensity
  • choroid proper - vascular and pigmented
  • ciliary body - produce aqueous humor (sometimes vitreous); lens held by suspensory ligament; contract to relax suspensory ligament and focus light
  • iris - has pigments and forms rim of pupil; constrictor and dilator muscles to control size of pupil
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8
Q

inner (retinal) layer

A
  1. pigmented (external stratum) - single layer

2. cerebral (internal stratum) - 9 layers

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9
Q

cornea

A

different refractory index than air - bending of light rays

-main refractive structure of eye

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10
Q

aqueous humor

A
  • posterior chamber –> anterior chamber
  • drains into spaces of fontana –> canal of schlemm –> episcleral veins
  • increase intraocular pressure w/o drainage –> can lead to glaucoma (leading cause of blindness)
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11
Q

lens

A

focusing bc its refractile power can be altered by suspensory ligament

  • relax suspensory –> lens thickens
  • presbyopia = lens becomes harder with age
  • cataract = opacification of lens
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12
Q

reina

A
  1. non-neural - light absorbing pigmented cells
  2. neural - the deep layer photoreceptors
  • transmit light energy to electrical energy
  • more rods on periphery than cones in the middle
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13
Q

retinitis pigmentosa

A

failure of pigmented epith. to take up debris –> damage to photoreceptors

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14
Q

retinal detachment

A

separation of pigment and photoreceptor layers –> blurred vision

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15
Q

rods vs. cones

A
  1. rods
    - sensitive to light - night vision, dim light
    - peripheral part - decrease towards macula
  2. cones
    - bright light - color vision and high visual acuity
    - middle part - fovea and macula
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16
Q

neurons of retina

A
  • 1st order neuron –> bipolar cells in retina
  • 2nd order neuron –> ganglion cells forming optic nerve
  • interneurons - 1. horizontal cell (b/w photoreceptor and bipolar) 2. amacrine cell (b/w bipolar and ganglion)
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17
Q

central area of the eye

A
  1. fovea - contains cones, area for acute vision, foveola for light focusing to cones
  2. macula lutea
18
Q

optic disc

A
  • where unmyelinated nerve fibers coming from ganglion exit to head to brain
  • fibers become myelinated when exiting
  • blind spot - no photoreceptors
19
Q

rods vs. cones pigment

A
  • rods - rhodopsin pigment –> broken down to retinal and opsin and restored by vit. A after absorption
  • cones - iodopsin pigment
  • outer segment of photoreceptor cells –> transduce light rays to electrical energy
  • inner segments –> contain mitochondria for energy
20
Q

what causes night blindness?

A

vitamin A deficiency reduces nocturnal vision bc it cannot restore rhodopsin

21
Q

what is the effect of intracranial pressure via CSF?

A

can compress optic nerve –> disc edema, papilledema, choked disc

22
Q

fibers from temporal and nasal side of eye

A
  • temporal fibers - travel to LGN w/o decussation

- nasal fibers - travel to opposite LGN after decussation

23
Q

route for left visual field

A

left visual field –> right optic tract –> right LGN –> right visual cortex

24
Q

route for right visual field

A

right visual field –> left optic tract –> left LGN –> left visual cortex

25
Q

where do some optic nerve fibers go instead of LGN?

A

pretectal area - mediate the pupillary light reflex

26
Q

central visual pathway of info.

A

LGN (contains 3rd order neuron) –> thalamocortical neurons to primary visual cortex in occipital lobe

27
Q

primary visual cortex ***

A
  • located above and below calcarine sulcus
  • upper visual field –> lower retina –> fibers travel ventrally in temporal lobe to terminate BELOW calcarine sulcus (lingual gyrus)
  • lower visual field –> upper retina –> fibers travel dorsally in parietal lobe to terminate ABOVE calcarine sulcus (cuneus)
  • surrounded by visual association cortex (complex info.)
28
Q

macula of the eye

A

post. in visual cortex
- center of eye - more visual acuity
- image also flipped

29
Q

ex. of nasal/temporal side - visual field

A

right visual field

  • nasal side of right eye
  • temporal side of left eye
  • vice versa for left
30
Q

what do upper visual fields have to travel around?

A

around inferior horn forming loop (Meyer’s loop)

-lesion in temporal lobe –> affect UPPER visual field

31
Q

field of vision

A
  • fixation point - where vision is focused
  • quadrants - projected on retina in reversed, inverted by lens
  • visual pathways past optic chiasm carry fibers from contralateral halves of visual fields
32
Q

anopsia

A

complete loss of vision

33
Q

homonymous defect aka contralateral homonymous hemianopsia

A

affect same parts of visual fields in both eyes

  • lesion distal to optic chiasm
  • lose entire opposite field of vision in both eyes
34
Q

heteronymous defect aka bitemporal hemianopsia

A

affect different parts of visual field of both eyes

  • lesions of optic chiasm - usually affect crossing fibers (nasal)
  • ex. affect left visual field of left eye and right visual field on right eye bc of decussation
35
Q

dorsal vs. ventral fiber lesions

A

dorsal fiber lesion –> affect lower visual field

ventral fiber lesion –> affect upper visual field

36
Q

light/pupillary constriction reflex

A

direct light reflex, can involve PNS

  • light exposure –> pupil constricts
  • consensual light reflex –> indirect pupil constriction in opposite eye
  • optic tract –> superior colliculus –> pretectal area –> edinger Westphal –> oculomotor nerve –> ciliary ganglion –> short ciliary nerve –> constrictor muscle of iris
37
Q

pupillary dilation reflex

A

passively by decreased PNS or actively by increased SNS (in hypothalamus)

  • post. hypothalamus –> ciliospinal center in spinal cord –> ventral route –> white rami communicating –> superior cervical ganglion –> carotid plexus –> nasociliary and long ciliary nerves to dilator muscles of iris
  • miosis if SNS is affected
38
Q

accommodation reflex

A

maintain clear image when shifting from far to near object

  • near triad: convergence, pupillary constriction, thicken lenses
  • increase curvature of lens (bulge), contract ciliary body relaxing suspensory lig.
  • increase visual acuity by convergence and constriction of pupil
39
Q

accommodation reflex pathway

A

stimulated by perception of object

  • occipital cortex –> corticotectal tract –> accomodation center –> oculomotor nuclei –> edinger westphal (pupil constriction –> oculomotor nerve –> ciliary ganglion –> short ciliary nerves –> iris constrictor muscles
  • OR…accomodation center –> oculomotor somatic nuclei (for convergence) –> medial rectus
40
Q

where is upper left visual field info. found?

A

found in lower right quadrant in visual cortex

41
Q

retinitis pigmentosa

A

inherited disease of photoreceptors and retinal pigment epith. cells –> night blindness
-need to remove pigment

42
Q

Horner syndrome

A

from tumors or vascular lesions

  • miosis, ptosis, anhydrosis
  • loss of smooth muscle innervation in upper eyelid and SNS innervation to sweat glands

BECOM II Exam 5 (24 decks)

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