PHYS physiology of the visual system

Question 1

where is the first site of refraction

Answer 1

cornea

accounts for 2/3 of light bending

Question 2

relationship between roundness and refraction

Answer 2

rounder = more refraction
flatter = less refraction

Question 3

what happens when ciliary m contracts

Answer 3

allows suspensory ligaments to loosen
allows lens to take a rounder shape
used for near vision

Question 4

what happens when ciliary m relaxes

Answer 4

suspensory ligaments tighten
causes a flatter lens shape
used for far vision

Question 5

presbyopia

Answer 5

lens becomes stiffer in aging, loss of elasticity

Question 6

5 types of neurons in the retina
vertically oriented
horizontally oriented

Answer 6

Vertical:
    receptor cells (rods and cones)
    bipolar cells
    ganglion cells (subtype:MG cells)
horizontal:
    horizontal cells
    amacrine cells

Question 7

where is the density of cone receptors the most

Answer 7

center of eye

rods-periphery-ish. peak at 20 degrees

Question 8

what NT do rods and cones release

Answer 8

glutamate

Question 9

when is glutamate release the highest (in what environment)

Answer 9

in the dark

photons in light stimulate and hyperpolarize the cells

Question 10

on center bipolar cells
what depols
what hyperpols
compare to off center bipolar cells?

Answer 10

activation of photoreceptors in the center of the bipolar cell’s receptive field depols
activation of photoreceptors in the periphery of the bipolar cell’s receptive field hyperpols
off center bipolar cells- opposite

Question 11

effects of glutamate receptor in depolarizing bipolars

Answer 11

GPCR that closes cGMP-gated ion channels similar to light transduction photoreceptors. channels open when less glutamate is present

allows for sign change – depol. leads to closure of
channel (opposite what you might think)
ON-center bipolars

Question 12

effects of glutamate receptor in hyperpolarizing bipolars

Answer 12

common, excitatory glutamate receptor (non-NMDA recptors: AMPA and kainate)
no sign change

OFF-center bipolars

Question 13

activation of an on center bipolar cell by a cone photoreceptor (in dark)

Answer 13

glutamate activates Gi GPCR-metabotropic receptor
results in decrease in cation influx (depolarizing bipolar)
hyperpolarizes cell

Question 14

activation of an on center bipolar cell by a cone photoreceptor (in light)

Answer 14

light decreases amount of glutamate present
less Gi signaling
increase of cation influx
depolarizes the cell

Question 15

activation of an off center bipolar cell by a cone photoreceptor (in dark)

Answer 15

glutamate activates AMPA
increase of cation influx
depol. of cell

Question 16

activation of an off center bipolar cell by a cone photoreceptor (in light)

Answer 16

light decreases amount of glutamate
less activation of AMPA
decrease in cation influx
hyperpol. of cell

Question 17

f(x) of on and off center cells

Answer 17

help us increase the ability to detect edges and sharpen our vision
on center – tells us where something is
off center – tells us where something ends

Question 18

direct targets of the retina (nuclei and structures)

Answer 18

LGN
superior colliculus
pretectal area
hypothalamus
accessory optic nuclei

Question 19

V1

Answer 19

primary visual cortex (brodmann area 17)

identify edges and contours of objects

Question 20

V2

Answer 20

greater part of brodmann 18

depth perception by analyzing the disparities between the two eyes

Question 21

V3

Answer 21

narrow strip of brodmann 18

identification of motion (3a)

Question 22

V4

Answer 22

area 19

complete processing of color inputs

Question 23

V5

Answer 23

middle temporal (MT) area (Part of 19)

Question 24

Dorsal pathway “where pathway”

Answer 24

from primary visual cortex to parietal/frontal cortex
primary path associating vision with movement
completes motor acts based on visual input
passes through V3

Question 25

Ventral pathway “what pathway”

Answer 25

from primary visual cortex to inferior temporal cortex
primarily involved with interpreting images and complex patterns
copying/naming objects are separate functions in the temporal lobe (damage to one area is possible without damage to the other)
facial recognition is a specialized area