Neuro Visual System

Front 1

Astigmatism?

Back 1

refractive index is different along 2 perpendicular axes

Front 2

Presbyopia?

Back 2

age-related affect when lens can't increase its convexity enough to bring near objects into focus

Front 3

Where do ganglion cell neurons synapse?

Back 3

lateral geniculate nucleus of thalamus then the principal neurons here send thalamocortical fibers to primary visual cortex via optic radiations

Front 4

What are optic radiations?

Back 4

path by which thalamocortical fibers of the principal neurons in lateral geniculate nucleus get to visual cortex

Front 5

Which retinal fibers cross to contralateral side?

Back 5

NASAL half cross (closer to middle anyways)
Temporal half do not cross (temporal part of right eye sees left visual world so no need to cross cause it has to go to right visual cortex)

Front 6

In the lateral geniculate body how do the axons from the ganglion cells synapse?

Back 6

axons from the 2 eyes remain segregated but synapse in alternate but retinoptically aligned layers (see i? i see i see)
Layers 1,4,6 from contralateral nasal retina
Layers 2,3,5 from ipsilateral temporal retina

Front 7

Which cell's axons synapse in layers 1 and 2 of lateral genicualte body?

Back 7

large M-type ganglion cells (afferent component of magnocellular subsystem

Front 8

Magnocellular subsystem?

Back 8

made up of large M-type ganglion cells
have wide-field representations that converge and are good at sensing motion
-works with area 19 motion system to direct visual attention and stereopsis

Front 9

Which cell's axons converge in layers 3-6 of lateral geniculate body?

Back 9

smaller P-type ganglion cells - form parvocellular subsystem

Front 10

What does the parvocellular system do?

Back 10

process form and color attributes

Front 11

Which fibers make up Meyer's loop?

Back 11

inferior fibers of optic radiations which represent the upper visual field

Front 12

Line of Gennaria?

Back 12

visual stripe produced by prominent myelinated afferents in layer 4 of visual cortex

Front 13

With relation to the calcarine fissure where is the upper visual field represented?

Back 13

upper field is BELOW fissure so lower visual field is above fissure

Front 14

Lesions in infracalcarine branches of posterior cerebral artery?

Back 14

cause visual agnosias like prosopagnosia or achromatopsia

Front 15

What do heteronomous field defects indicate?

Back 15

lesion at or anterior to chiasm

Front 16

Lesions where cause homonomous field defects?

Back 16

lesions behind the chiasm in the tracts, LGN, optic radiations, or cortex

Front 17

How would a temporal lobe lesion affect the visual field?

Back 17

lesions here could interfere with the inferior fibers of Meyer's loop which would produce homonomous superior field defects

Front 18

Macular sparing?

Back 18

accompanies homonomous hemianopia with lesions specific to occipital pole
-may be causes by a PCA stroke because collateral flow from MCA gets other fibers

Front 19

What may cause a left nasal hemianopia?

Back 19

expansion of carotid artery

Front 20

What may cause a bitemporal hemianopia?

Back 20

pituitary problem

Front 21

Where do the axons repsonsible for the pupillary light reflex synapse?

Back 21

in pretectal nucleus after bypassing the lateral geniculate via the brachium of the superior colliculus

Front 22

Where do fibers go from the pretectal nucleus?

Back 22

to bilaterally innervate Edinger-Westfall nucleus via posterior commissure - bilateral innervation responsible for consensual reaction

Front 23

What does each Edinger-Westfall nucleus supply?

Back 23

parasympathetics to ipsilateral pupillary constrictor via ciliary ganglion

Front 24

From the posterolateral hypothalamus how do fibers get to ciliospinal center in C8-T1 region of spinal cord?

Back 24

descend ipsilaterally through red nucleus, pontine tegmentum, and reticular formation

Front 25

What are the 3 components of the accomodation reflex?

Back 25

1. contraction of ciliary muscle (lens thickening)
2. pupillary constriction (miosis)
3. convergence of 2 eyes (medial recti)

Front 26

Where does the accommodation pathway begin?

Back 26

striate/peristriate cortex aka area 19 then passes to premotor frontal cortex and descends via internal capsule to oculomotor region

Front 27

What is innervated by the accommodation pathway?

Back 27

-motorneurons of medial rectus subnucleus of III
-preganglionic parasympathetic neurons of Edinger-Westfall nucleus for contraction of pupillary and ciliary muscles

Front 28

Horner's syndrome?

Back 28

ipsilateral sympathetic lesion resulting in pupillary constriction, ptosis, and ansence of sweating

Front 29

Tonic (Adie's) pupil?

Back 29

unilateral pupil dilation unresponsive to direct or consensual stimulation
-caused by peripheral lesion, esp. in postgang. parasympathetic outflow from E-W nucleus

Front 30

Argyll-Robertson pupil?

Back 30

pupils lose light reflex but maintain accomodation
-caused by lesion in pretectal region that disturbs light reflex pathway to E-W but not the accommodation

Front 31

Horizontal and amacrine cells?

Back 31

-horizontal cells are interneurons of outer plexiform layer
-amacrine cells are interneurons of inner plexiform layer
-together they interact and allow detection of local contrast

Front 32

Steps in phototransduction?

Back 32

-light hits photoreceptor and activates pigment
-this stimulates G-protein (visual pigment is G-protein coupled receptor controlling cGMP phosphodiesterase)
-G-protein activates cGMP phosphodiesterase which breaksdown cGMP to GMP
-lowered cGMP concentration in outer segment cause the cGMP-gated channels to close
-inward current reduced and photoreceptor hyperpolarizes

Front 33

Where does the basic spatial organization of ganglion cell receptive fields occur?

Back 33

outer plexiform layer (ganglion cells found in ganglion cell layer)

Front 34

Layer 4 of the visual cortex gets most of the inputs from the LGN, but what happens in layers 2,3,5,6??

Back 34

-Layers 2 & 3 fibers to extrastriate cortical regions
-Layer 5 to superior colliculus, pulvinar, pons
-Layer 6 to LGN, claustrum