Visual system Flashcards
Chapter 2.2
what kind of resolution do the parvocellular cells of the thalamus have?
high spatial resolution
what structure of the eye controls the amount of light coming in?
iris
damage to the optic chaism results in…
because the crossing optic nerve fibers come from the nasal retina, the lateral (temporal) visual field is affected
each nasal pathway stays on the same side, but the temporal pathways cross over
optic chiasm is where signals from the nasal and temporal retina cross o
select all that are true about rods
a. rods are in the fovea in high density
b. rods make up majority of photoreceptor cells in the eye
c. visual pigment of rods is rhodopsin
d. rods primarily contribute to scotopic vision
b, c, d are correct
a is wrong, no rods in the fovea where there is cones instead
scotopic vision - vision under low light
interposition
when one object covers or obscures another, where the one that covers the other is closer
motion parallax
when closer objects seem to move faster than distant objects
linear perspective
paralllel lines appearing to converge with distance
somatosensation
several components of touch, sense pressure, vibration, pain, temperature not smell
obstruction of nasal mucus membrans means
signals from the olfactory path are not reaching the olfactory bulb
nocioception, mechanoreception, somaticsensation, proprioception
nocioception - pain mechanoreception - pressure, vibration
somaticsensation - detecting tactile simuli (touch)
proprioception - balance
when an object seems pink it means
all other colors are absorbed from the light and pink is reflected
cornea, aqeous humor, lens, vitreous humor, pupil, iris, cillary muscles
lens - allows light in
cornea - thick layer of protection
aqueous humor - before the lens
vitreous humor - inside the eye
pupil - opening for light
iris - flat ring shaped muscle with dilater (opens) pupil for more light or sphincter (close) pupil for less light
cillary muscles - changes shape of lens to make light reach retina
if eye is too short..
lens cant bend light enough to focus it on the retina
(farsideness or hyperopia)
if eye is too long…
lens cannot bend light to avoid overshooting retina
near sidedness or myopia
retina recieves.. what kind of image and has…what kind of receptors
a flipped image
rod - light in green/ blue in low light, at night
cone - full color with sufficient light
20X more rods than cones in retina primarily in periphary than cones in the central
fovea has only cone cells
macula and fovea
The macula is part of the retina at the back of the eye. It is only about 5mm across, but is responsible for our central vision, most of our colour vision and the fine detail of what we see.
The fovea centralis is located in the center of the macula lutea, a small, flat spot located exactly in the center of the posterior portion of the retina. As the fovea is responsible for high-acuity vision it is densely saturated with cone photoreceptor
- only cone cells
phototransduction
process by which rod and con cells convert photons of light into electrical signals at the retina
due to opsins, photoreceptive pigments
rhodopsin in rods
photopsin in cones for color photos
bipolar, amacrine cells, horizontal cells
build back up to center of the eye backwards
bipolar cells connect cones, rods and blend into gradient for ganglion cells
horizontal are inhibitory and point out differences at edges
horizontal connect to amacrine and send edge detection
how to visual projections work?
right vf –> left retina
left vf –> right retina
