Chapter 6.1: EYE Remote Sensing

Question 1

light is bent by the __ and ___

Answer 1

bent by the lens and cornea

Question 2

why is an inverted image projected onto the retina?

Answer 2

bc light converges and crosses just behind the lens, which causes an inverted image to be projected onto the retina.

Question 3

if someone is near sighted, the image gets focused ____ of the retina

Answer 3

infront of the retina

Question 4

if someone is far sighted, the image gets focused ___ the retina

Answer 4

behind

Question 5

accomodation is facilitated by ____ ____ that can bend the lense for focusing

Answer 5

intraocular muscles

Question 6

cells that act as the visual system’s transducers by converting light energy to neural signals

Answer 6

photoreceptors

Question 7

transduction

Answer 7

transforming energy input from environment and recording it as electrical input of neural firing in sensory axons.

Question 8

blood vessels that line the retina all project from the ___ ___

Answer 8

blind spot

Question 9

axons carrying info out of the retina to the brain initially run along the inside of the retina and enter the ___ ___ by crossing through the depth of the retina. The cross over at the ___ ___ ___ is the blind spot, which is devoid of ___

Answer 9

axons carrying info out of the retina to the brain initially run along the inside of the retina and enter the OPTIC NERVE by crossing through the depth of the retina. The cross over at the OPTIC NERVE HEAD is the blind spot. Devoid of PHOTORECEPTORS

Question 10

why are we unaware of our blindspots?

Answer 10

because the blindspots on our 2 eyes are aimed at different regions of space and we fill in the parts of the retinal image.

Question 11

___ ia the region of darkly pigmented retina that contains the center of the visual field, the ____.

Answer 11

MACULA is the region that contains the FOVEA: the center of the visual field.

Question 12

The fovea has a high density of

Answer 12

cones

Question 13

macular degeneration

Answer 13

degeneration of the center of your visula field. You can’t see things directly in front of you, but you have peripheral vision

Question 14

T/F: Rods fire APs

Answer 14

false

Question 15

Instead of dendrites, what do rods and cones have?

Answer 15

they have short axons and contain rod shaped (or cone shaped) outer segments instead of a dendrite.

Question 16

In rods, the outersegment is filled with ____. What 2 molecules is it made of?

Answer 16

filled with rhodopsin. Made of retinal (G protein) and opsin (the GPCR)

Question 17

What does opsin do?

Answer 17

Opsin acts as a GPCR that gets stimulated by light. after opsin (in the outersegment of a rod) absorbs a photon, it converts RETINAL protein from CIS to TRANS and detaches retinal from opsin.

Question 18

G protein retinal is converted from ___ to ___ configuration after the activation of ___ GPCR

Answer 18

retinal gets converted from cis to trans by OPSIN G protein receptor

Question 19

explain the phototransduction cascade in a rod cell

Answer 19

normally, rod cells are turned on by the dark!

when outersegment gets reconfigured from CIS to TRANS by opsin absorbing a photon, rhodopsin activates transducin, a G PROTEIN.

Transducin exchanges GDP for GTP, causing it’s alpha subunit to dissociate and activate PHOSPHODIESTERASE

Phosphodiesterase decreases cGMP amount by breaking it down to GMP

Decreases in cGMP CLOSES cGMP cation channels, and DECREASES rate of Na+ and Ca2+ influx into the PHOTORECEPTOR

the PHOTORECEPTOR Is thus HYPERPOLARIZED in response to light

Question 20

the rod photoreceptor gets _____ in response to light,resulting in a decrease of ___ release.

Answer 20

rod photoreceptor gets HYPERPOLARIZED in response to light, resulting in a DECREASE of GLUTAMATE release.

Question 21

If light hyperpolarizes rod cells, how does this initiate an excitatory response in rod bipolar cells?

Answer 21

rod BIPOLAR cells contain metabotropic GLUT receptors that actually cause HYPERPOLARIZATION in response to glut release by rod photoreceptors.

Therefore, in the dark, when rods are release glut, the bipolar rod cells are hyper polarized and inactive

but in the light, when the rods don’t release as much glut, the inhibitory glut receptors of the rod bipolar cells are INACTIVE, and thus the ROD BIPOLAR CELL DEPOLARIZES IN RESPONSE TO LESS GLUT STIMULATION. This results in more neurotransmitter release (excitatory) response of the bipolar cells.

Question 22

What is dark adaptation

Answer 22

after prolonged exposure to darkness, retinal in the rods are all in CIS form, and recombined with opsin to form intact rhodopsin. Because all the rods are in “ready” conformation, they can be activated by a single photon and are very sensitive to any light.

Question 23

which wavelength of light do rods respond best to?

Answer 23

rods respond maximally to blue green wavelengths but they are not used in color vision.

Question 24

3 types of cones

Answer 24

1) S cones: respond to short wavelengths (blue
2) M cones: respond to middle wavelengths (yellow/green)
3) L cones: respond to ong wavelengths (red).

Question 25

color blindness typically results as a deficiency in ___ and ___ cones

Answer 25

M or L cones

Question 26

protanopic dichromatic color blindness

Answer 26

red green color blindness (missing L cone)

Question 27

tritanomic dichromatic color blindness

Answer 27

missing short wavelength cone (yellow blue blindness)

Question 28

what is additive mixing?

Answer 28

overlapping 3 spectra of LIGHT to produce white

Question 29

what is subtractive mixing

Answer 29

overlapping 3 spectra of PIGMENT to produce black

Question 30

rods synapse to ____ rod bipolar cells

Answer 30

ON rod bipolar cells only. this means they get ACTIVATED by light (decrease glut release from photo receptor causes activation of bipolar cell and thus more APs)

Question 31

what is a negative afterimage?

Answer 31

the image seen after a portion of the retina is exposed to intense visual stimulus; consists of colors complementary to those of the physical stimulus.

Question 32

a negative afterimage results due to the ___ ___ model

Answer 32

opponent process model:colors can interact with one another in a mutually inhibitory way

Question 33

what are complimentary colors

Answer 33

colors that make white or grey when mixed together

Question 34

trichromatic theory of color

Answer 34

the idea that all colors can be made by the 3 primary colors which correspond to the cones

Question 35

when red light stimulates a red cone, ___ ___ inhibit the complimentary cell cone (which is __)

Answer 35

horizontal cells inhibit the complimentary cone cell (green)

Question 36

in terms of fatigue, how does a negative afterimage arise?

Answer 36

due to the fatiguing of the cones that fire in response to the original color (and horizontal cells that are inhibiting the complementary color), so there is nothing inhibiting the opposing cone from firing. Ex/ looking at a green image fatigues the green cone and prevents red-green ganglion inhibition, making you see red).

Question 37

you see yellow when there is simultaneous excitation of ___ and ___ cones

Answer 37

red and green.

Question 38

two types of cone ganglion cells

Answer 38

red-green (red and green cones synapse to it) and yellow-blue (blue cones synapse to it)

Question 39

inhibition of the red-green GANGLION results in seeing ___, what about excitation?

Answer 39

inhibition of red-green ganglion results in SEEING GREEN

excitation of red-green ganglion results in SEEING RED.

Question 40

inhibition of the blue-yellow ganglion results in seeing ___ What about excitation?

Answer 40

inhibtion of the blue yellow ganglion results in seeing BLUE

excitation of the blue yellow ganglion results in seeing YELLOW

Question 41

Why do you see yellow when both the green and red cones are simultaneously stimulationed?

Answer 41

green cone stimulation results in INACTIVATION of redgreen ganglion

red cone stimulation results in ACTIVATION of red green ganglion

these two cancel each other out, therefore the only active cone is blue, which signals YELLOW when the blueyellow ganglion gets excited.

Question 42

In response to light, cones ___ glutamate release

Answer 42

DECREASE

Question 43

for cones:

Decreasing glutmate release by cones in response to light causes DEPOLARIZATION of ___bipolarcells , which is metabotropic, and causes HYPERPOLARIZATION of ___bipolar cells, which are ____

Answer 43

Decreasing glutmate release by cones in response to light causes DEPOLARIZATION of ON-bipolarcells , which is metabotropic, and HYPERPOLARIZATION of OFF bipolar cells, which are ionotropic.

Question 44

on an OFF cone bipolar cell, it is _____ when light is OFF.

Answer 44

DEPOLARIZED when light is off. When light is off, there is sufficient glutamate release by the photo receptor (dark detector)

Question 45

on an ON cone bipolar cell, it is ___- when light is OFF and ____ when light is ON.

Answer 45

HYPERpolarized when light is off (glutamate release by photoreceptor has an inhibitory effect on metabotropic receptor) and DEPOLARIZED when light is ON (less glutmate release causes excitation)

Question 46

cone bipolar cells synapse directly to ____ ___ ___ which project through the ___ ___.

Rod bipolar cells synapse with ___ cells instead, that also synpase to cone cells.

Answer 46

cone bipolar cells synapse directly toRETINAL GANGLION CELLS which project through the OPTIC NERVE to various parts of the brain

Rod bipolar cells synapse with AMACRINE cells instead, that also synapse to cone cells.

Question 47

rod bipolar cells synapse to amacrine cells, which also synapse to ON and OFF cone bipolar cells. amacrine cell uses ____ to ___ OFF Cone cells, and uses ___ ___ to ___ ON bipolar cells.

Answer 47

rod bipolar cells synapse to amacrine cells, which also synapse to ON and OFF cone bipolar cells. amacrine cell uses GLYCINE to INHIBIT OFF Cone cells, and uses ELECTRICAL SIGNALS to EXCITE ON bipolar cells.

**off cone cells turn off in response to light. (depolarize in response to darkness). Turning off the OFF cone cell by means of amacrine synapse stimulation means the rod is detecting light, aiding the off cone cell to turn off.

Question 48

Cones have a ___ receptive field, what does this allow for? How is this receptive field created?

Answer 48

Cones have a small receptive field, allowing for heightened acuity and visual resolution (in the center of your visual field). This is because one cone cell synapses onto one cone bipolar cell.

Question 49

rods of a ____ receptive field. What does this allow for? how is this receptive field created?

Answer 49

rods have a LARGE receptive fied. This reduces spatial resolution and acuity but the synapsing of multiple rods onto a rod bipolar cell makes rod bipolar cells very sensitive to light since it gets a lot of input.

Question 50

What is the visual receptive field?

Answer 50

a region of visual field in hich the presentation of a visual stimulus will alter the activity of a particular region

Question 51

what is the choroid

Answer 51

a dense capillary network near the retina

Question 52

the choroid allows for retinoid recycling. what is thiis?

Answer 52

trans-retinal that was activated by light is transported out of the photoreceptors into pigment epithelium where it is re-isomerized to cis retinal and recombined with opsin.

Question 53

purpose of muller cells

Answer 53

collect incoming light at the retina inner surface and channels it past the choroid straight to the photoreceptors.

Question 54

what is the purpose of tapetum luadum in nocturnal animals?

Answer 54

it is a reflective layer in the choroid. Sometimes photos get past the photoreceptors without being captured by opsin. Light bounces off the tapetum to get another chance to interact with opsin. this increases the ability to see in low light conditions.