Sight (vision)

Question 1

Conjunctiva

Answer 1

thin layer of cells that lines the inside of your eyelids from the eye.

Question 2

Cornea

Answer 2

transparent thick sheet of fibrous tissue, anterior 1/6th; starts to bends light,
first part of eye light hits.

Question 3

Anterior chamber:

Answer 3

space filled with aqueous humour, which provides pressure to maintain shape of eyeball; allows nutrients and minerals to supply cells of cornea/iris.

Question 4

Pupil:

Answer 4

the opening in the middle of the iris. The size of the pupil can get bigger/smaller based on the iris relaxing/contracting respectively. The pupil modulates the amount of light able to enter the eyeball.

Question 5

Iris:

Answer 5

Gives the eye color. The muscle that constricts/relaxes to change the size of the pupil.

Question 6

Lens

Answer 6

bends the light so it goes to back of eyeball – focuses light specifically on the fovea of the retina. Adjust how much it bends the light by changing its shape, using the suspensory ligaments.

Question 7

Suspensory ligaments:

Answer 7

attached to a ciliary muscle. These two things together form the ciliary body, what secrets the aqueous humor.

Question 8

Posterior chamber:

Answer 8

area behind the iris to the back of lens; also filled with aqueous humor.

Question 9

Vitreous chamber:

Answer 9

filled with vitreous humour, a jelly-like substance to provide pressure to eyeball and gives nutrients to inside of eyeball.

Question 10

Retina:

Answer 10

inside, back area filled with photoreceptors, where the ray of light is converted from a physical waveform to a electrochemical impulse that the brain can interpret.

Question 11

Macula:

Answer 11

special part of retina rich in cones, but there are also rods.

Question 12

Fovea

Answer 12

special part of macula. Completely covered in cones, no rods.
*Rest of the retina is covered in primarily rods

Question 13

Cones:

Answer 13

Detect color and discern high level of detail in what you are observing. Cone
shaped.

Question 14

Rods:

Answer 14

Detect light. Rod shaped.

Question 15

Choroid

Answer 15

pigmented black in humans, is a network of blood vessels that helps nourish
the retina. It black all light is absorbed. Some animals have a different colored choroid
which gives them better night vision.

Question 16

Sclera –

Answer 16

Usually absorbs by the time the light gets to this. The whites of the eye, thick
fibrous tissue that covers posterior 5/6th of eyeball (cornea covers the anterior 1/6). Attachment point for muscles. Extra layer of protection and structure of eyeball. Lined with the conjunctiva.

Question 17

Transmission

Answer 17

is the electrical activation of one neuron by another neuron.

Question 18

Perception

Answer 18

is conscious sensory experience of neural processing.

Question 19

Processing

Answer 19

is the neural transformation of multiple neural signals into a perception.

Question 20

Transduction

Answer 20

occurs whenever energy is transformed from one form to another; in this
case, light energy is transformed to electrical energy by rods and cones.

Question 21

Sensation

Answer 21

requires a physical stimulus to be converted into a neural impulse.

Question 22

In the case of the eye, light is being converted to a

Answer 22

neural impulse by a photoreceptor

Question 23

What is light?

Answer 23

Light is an electromagnetic wave.

Question 24

Visible light

Answer 24

Violet (400nm) – Red (700nm). Highest to lowest wavelength: ROYGBV

Question 25

3 types of cones

Answer 25

red, green and blue

Question 26

There are 120 million rods, for night vision Light comes in, goes through pupil, and hits rod. Normally rod is turned __, but when light hits turns __

Answer 26

on
off

Question 27

Bipolar cells

Answer 27

found in the rentina

these cells send visual signals from rods and cones to the ganglion cells

Question 28

Phototransduction cascade: what happens when light hits rod/cone

Answer 28

1) Light hits rods (which causes rod turns off)
2) a bipolar cell (turns on)
3) retinal ganglion cell (turns on)
4) goes into optic nerve
5) enters BRAIN.

Question 29

trichromatic theory of color vision

Answer 29

theory states that you have cones that are receptive to 3 colours (R,G,B) these three colors are. mixed together and you precieve colour

Question 30

Problem with the trichromatic theory of color vision

Answer 30

although out eyes can miz red and yellow to make orange, we can seem to mix red and green or blue and yellow

Question 31

what theory explain the problem with the trichromatic theory of color

Answer 31

opponent process theory of color vision

Question 32

what is the opponent process theory of color vision

Answer 32

you have cones that perceive 4 colour, R,G,B,Y

red and green oppose each other

blue and yellow oppose each other

black and white sensitive cones oppose each other

between the opposing color only one colour can be dominate at a time

Question 33

The Phototransduction Cascade (PTC)

Answer 33

makes the brain recognize that there is light entering the eyeball. The process of making the light -> neural impulse by turning off a rod. The neural impulse can turn on other cells and eventually be processed by the brain.

Question 34

rods are normally on or off?

Answer 34

on

Question 35

what happens when light hits a rod turns on or off

Answer 35

off

Question 36

steps of The Phototransduction Cascade

Answer 36

Phototransduction cascade is the act of turning the rod cell OFF which signals to the brain that light is entering the eye.

Phototransduction cascade goes like this:

In the absence of a light rod is turned ON.

Rods contain rhodopsin (a GPCR) which contains 11 cis retinals.

when the light hit, comes through the pupil, and hit the retinal, it rod, some of the light hits the rhodopsin (which contains the retina) and causes it to change conformation from bent to straight (11 trans retinal)

when the retinal changes shape, rhodopsin changes shape this begins the cascade

a molecule called transducin (three parts alpha, beta, and gamma) is attached to the rhodopsin

when the rhodopsin changes shape the transducin breaks from the rhodopsin and the alpha subunit binds to another disk protein called phosphodiesterase (PDE)

PDE takes cGMP and converts it to GMP

lots of Na+ channels on the rods allow Na+ ions to come in

cGMP bound to Na+ channel keeps the channel open and hence “ON”,

as cGMP concentration decreases, the na+ channel close and the cell turns OFF

when Na+ channels become unbound of cGMP, less na+ enters the cell the cell hyperpolarization and turns OFF

Next, bipolar cells (two variants: ON CENTER and OFF CENTER).
* When light hits ROD, turned off –> ON CENTER bipolar cells active, OFF CENTER bipolar cells inactive.
* When ON CENTER bipolar cells are turned on, this activates ON CENTER retinal ganglion cell, which sends a signal to optic nerve to brain.

Question 37

Photopic vision occurs

Answer 37

at levels of high light levels.

Question 38

Mesopic vision occurs at

Answer 38

dawn or dusk and involves both rods and cones.

Question 39

Scotopic vision occurs

Answer 39

at levels of very low light.

Question 40

A photoreceptor

Answer 40

is a specialized nerve that can take light and convert to neural impulse.

Question 41

Inside rods are

Answer 41

optic discs, which are large membrane-bound structures – thousands of
them. In the membrane of each optic disc are proteins that fire APs to the brain

Question 42

Cones are also specialized

Answer 42

nerves with same internal structure as rod.

Question 43

Rods contain

Answer 43

rhodopsin

Question 44

Cons Contain

Answer 44

photopsin.

Question 45

If light hits a rhodopsin, will trigger the

Answer 45

phototransduction cascade. Same process
happens in a cone.

Question 46

Differences between rods and cones:

Answer 46

MORE RODS THAN CONES
Cones are concentrated in the fovea
Rods are 1000x more sensitive to light than cones.
Cones detect color primarily but also some light (three types : 60% Red, 30%
Green, 10% Blue)
Rods have slow recovery time vs. cones have fast recovery time

Question 47

blind spot

Answer 47

Where optic nerve connects to retina, blind spot – no cones or rods.

Question 48

Rods are found mostly

Answer 48

periphery.

Question 49

Cones are found primarily

Answer 49

Cones are found primarily in the fovea, and few dispersed through the rest of eye.

Question 50

At the fovea (dimple in retina) light hits cons directly beacuse ?

Answer 50

there no axons in way of light so get higher resolution.

Question 51

At the periphery, less light gets to the rods. why?

Answer 51

At the periphery - light has to go through bundle of axons and some energy lost.

Question 52

All right visual field goes

Answer 52

left side of brain;
vise versa

Question 53

light travel from the left side visual field?

Answer 53

Ray of light from the left visual field hits the NASAL side of the left eye and hits the TEMPORAL side of the right eye

Vice Versa for light from the right visual field. Ray of light from the right visual field hits the NASAL side of the right eye and hits the TEMPORAL side of the left eye

Question 54

Optic nerves

Answer 54

from each eye networks the electrical signal to the brain and converge from each eye at the optic chiasm and then break off and dig deeper into the brain

Question 55

Feature Detection:

Answer 55

When looking at an object, you need to break it down into its component features to make sense of what you are looking at. There are 3 things to consider when looking at any object: color, form, and motion.

Question 56

What detects form/shape?

Answer 56

Parvocellular pathway: good at spatial resolution (boundaries and shape—high levels of details), and color. But poor temporal (can’t detect motion—only stationary.)

Cones responsible

Acronym: Pink Pyramid (a type of “form”/”shape”) = Parvocellular pathway

Question 57

what detects motion?

Answer 57

Magnocellular pathway: has high temporal resolution (think time,
motion) resolution [encodes motion]. But has poor spatial resolution; no
color).
Rods responsible.

Acronym: Motion = Magnocellular pathway

Question 58

Parallel Processing:

Answer 58

detect/focus all information (color, form, motion) at same time.