vision science midterm

photo-isomerization of rhodopsin results in (select 3)

1) hyperpolarizing graded potential

2) decrease in glutamate release

3) closure of sodium channels along the outer segment

WOTF statements about properties of central vision are correct? (select 3)

1) the macula and ambler grid are each 20 degrees across

2) L, M, and S cones photopigments are erythrolabe, chlorolabe, and cyanolabe respectively

3) in 1.5 minutes, 50% of the cone photopigment regenerates to the unbleached state

absorption of light by a rod photoreceptor results in (select 3)

1) increased activity of a protein known as transduscin

2) dis-inhibition (activation) of the enzyme phosphodiesterase

3) closure of the outer segment sodium channels

which statements about visual processing is correct?

the area of V1 which processes macular information is disproportionately large but IS consistent with the retinal distribution and number of ganglion cells

most cells in the primary visual cortex (V1) (select 3)

1) are binocular; respond to stimulation of the other eye

2) respond to stimulus orientation

3) respond to a narrow range of spatial frequencies (stimulus sizes)

stimulus properties which are first processed before signals reach the visual cortex include (select 2)

1) color (chromatic) opponency

2) center-surround spatial antagonism

which statements about magno and parvo pathways is correct? (select 3)

1) LGN magno axons project to the upper layer of 4C in V1

2) parvo neurons show a sustained firing rate to stimulation

3) LGN parvo axons project to the lower layer of 4C in V1

describe a normal duplex dark adaptation curve

the cone portion is at the top, there is a rod cone break, and then the rod portion at the bottom. the very end of the rod portion is the absolute threshold.

describe a dark adaptation curve for a rod monochromat

no cones, single curve, normal scotopic threshold, no photopic threshold, poor color vision, rods peak at 507 nm

describe a dark adaptation curve for a cone monochromat

no rods, single curve (higher than rod monochromat), cones peak at 555 nm, normal phototopic threshold, no scotopic threshold

every 5 minutes _____% of rhodopsin (rods) regerenates

50

every 1.5 minutes ____% of cone photopigment regenerates

50%

scotopic

rods

photopic

cones

principal of univariance

once a photon is absorbed all sensitivity is lost

photo-chromatic interval

the difference between the rod/curve interval

every 5% change in rods being bleached causes a ___x change

10

every 10% bleaching of cones causes a ___x change

2

rod density peaks __ degrees from fixation

20

cone density peaks at the

fovea

there are more _____ than _____ (r/c)

rods, cones

what does the outermost layer of the retina do?

RPE - single layered cells, structure, high electrical resistance (+ front, - back), fluid regulation, have apical/basal membranes, phagocytize rods/cones

the outer nuclear layer of the retina includes

rods and cones (ONL)

rods/cones connect directly to _____ and ____ cells

bipolar, ganglion

horizontal cells attach themselves between

photoreceptors and bipolar cells

amacrine cells attach themselves between

bipolar and ganglion cells

the inner nuclear layer contains

horizontal, amacrine, and bipolar cells

regeneration of retinal (photopigment) is

cyclic

illuminance

amount of light on a surface/photos per surface

illuminance changes by

the square of the distance changed (2 feet will change illuminance by 4x)

on an amsler grid each square represents _ degree

1

__and __ cones are more prevalent than __ cones

L,M,S

stiles-crawford effect

cones are conical in shape to make light looks more specific to the object

which statements about AMD are correct?

• usually 50 years old

• vitamin C, E, beta-carotene, zinc, and Cu led to 25 decreased progression

• short wavelengths like UV and blue light can contribute

• antioxidants are good

• free radicals/reactive cells are bad

how to calculate retinal illuminance

(pupil size in dark/pupil in light) squared

luminance _____ change with distance

does not

absorption of light by a rod photoreceptor results in

increase in transducin, and retinal transitions from 11-cis to all trans

the retinal cell receptive field property known as spatial antagonism is

critical for detecting perceptions over a 10 log unit range, used to see differences that define an object

on-center bipolar cells show an inhibitory, hyperpolarixing response when luminance is :

increased on the center and decreased on the surroundings

off-center bipolar cells show an excitatory depolarizing response when luminance is :

decreased in the center and increased in the surroundings

list properties of midget ganglion cells

• 80-90% of ganglion cells

• sustained response to light

• respond to small high contrast colored stimuli

• project to dorsal parvo cellular layers

• respond oppositely to L and M cells

list properties of parasol ganglion cells

• 10% of ganglion cells sustained

• motion

• large receptive field

• transient response to light

• large low contrast, brief stimuli

• projects to ventral magno cellular LGN layer

neural transmission from eye to brain includes :

1) receptive fields become more complex as we ascend pathways

2) so much info requires parvo and magno pathways (parallel processing)

3) transducin disinhibits enzyme PDE (phosphodiesterase)

4) koniocellular

the LGN receives :

parvo → dorsal layers (3-6)

magno → ventral layers (1-2)

1,4,6 layers are contralateral, inf ret

2,3,5 are ipsilateral, temp ret

V1 neurons

• respond to orientation

• smooth neurons are inhibitory and are inhibited by GABA

• spinal neurons release glutamate

• 80% excitatory/20% inhibitory

if left side of head had an injury damaging layers 3-6 on the left LGN, then ___________

right VF will decrease (decreased VA and color perception)

a pituitary tumor pressing on the optic chiasm has damaged axons from ganglion cells projecting to layer 1 of each LGN. the patient will most likely have a ___________

bitemporal field defect and decreased motion bitemporally (magno)

your patient undergoes a vision test that requires the she detect low contrast motion. this test is evaluating

potential magno defects, FDT testing, larger neurons/axons go to ventral layer 2 of LGN

which statements about the human brain are correct?

• sulci/gyri fold up, high surface area

• superficial grey matter (cell bodies), underlying white matter (myelinated fibers/axons)

• synapses>cells

which statement about receptive fields and neural conduction is correct?

• receptive fields - areas of VF where light excites the cell

• rods/cone hyperpolarize to light and decrease glutamate

• only amacrine and ganglion cells have action potentials

ganglion cells which project to koniocellular layers of the LGN

• S cones

• blue/yellow pathway

which statements about visual area (V1) are correct?

• V1 - 6 layers

• also called striae cortex/area 17

• binocular

• 80% excitatory/20% inhibitory

• layer 4 is the main input to V1

where does conscious visual perception take place?

V1 occipital lobe visual cortex

a color opponent red-on (red plus), green-off (green minus) ganglion cells which project responds with

color opponency, increase/excite to red and decrease/inhibit to green. more excitable in the center

new stimulus properties first processed in the visual cortex :

• binocularity

• orientation in cortex

• direction

red cones

L, erythrolabe

green cones

M cones, chlorolabe

blue cones

S cones, cyanolabe

_________ increases with age

lipofuscin

mesopic vision is mediated by

rods and cones