Vision

Question 1

how do we perceive unified world

Answer 1

perception based on pattern and freq with which a limited number of specialized receptors fire, in conjunction with expectations and previous experiences

Question 2

path from eye to brain

Answer 2

light enters eye via pupil
cornea projects to retina at back of eye
retina lined with photoreceptors
photoreceptors are sensory neurons stimulated by light
no picture hits retina, just light frequencies

Question 3

retina is upside down and backwards

Answer 3

light from above hits bottom of retina and vice versa; from right, hits left, etc.

Question 4

types of retinal cells

Answer 4

bipolar
horizontal
amacrine
ganglion: all info passes through ganglion to brain
these 4 interneurons are all in front of retinal cells. light needs to pass thru pupil, lens cornea, vitreous humor then through interneurons

Question 5

fovea

Answer 5

center of retina
little dip where there are no interneurons covering retinal cells
light hits photoreceptors almost directly
vision from fovea is very acute and detailed
don’t perceive that vision is different
if something moves in front of you you move your eyes and head…trying to get it into fovea

Question 6

rods

Answer 6

black and white
active in dim light
more 20x rods than cones
not on fovea
peripheral vision
more sensitive to light....need less to send message
if lose rods, you are night blind
not interpreted as color
look at stars on an angle, will see better with periphery that need less light

Question 7

cones

Answer 7

higher acuity
day vision
color vision
better temporal resolution
  detect movement better
3 types: red (long 558), green (med 530) blue (short 420) - maximum response to these freq; less to other freq
need a lot of light or will not send message
  won't send message in dark
have a lot in fovea
also some scattered elsewhere

Question 8

photopigments

Answer 8

chemicals that change in response to light

each type of rods and cones needs different photopigment

Question 9

Rhodopsin

Answer 9

when not struck by light, contains 11-cis-re
tinal.  made from vitamin A.
in light, changes to all-trans-retinal
need this to be sensitive to light
do not make vitamin A, get it from diet
  really need carrots

Question 10

young-helmholtz theory

Answer 10

trichromatic theory of light

Question 11

what happens when light comes on?

Answer 11

11-cis-retinal changes to all-trans-retinal.
also have a lot of cGMP in photoreceptors
causes sodium ion channels to close
sodium stops moving
cell becomes hyper polarized
releases inhibition on interneurons
thus light photoreceptors STOP firing