Sight (vision)

Question 1

sclera

Answer 1

• white part of the eye
• think fibrous tissue that forms substance of the eyeball
• protects eye
• attachment point for muscles

Question 2

cornea

Answer 2

• transparent
• protected by thin layer of epithelial cells
• bends light
• ex. water- things are blurry because light ray is bent a different amount if passing through water (goggles add layer of air)

Question 3

conjunctiva

Answer 3

• protects cornea from dust
• thin layer of epithelial cells
• moisturizes cornea

Question 4

aqueous humor

Answer 4

• chamber filled with fluid
• water and salt
• fills in anterior chamber of the eye

Question 5

lens

Answer 5

• when light ray hits lens, it bends

- lens can change shape- thinner or thicker depending on how far away object is

Question 6

ciliary body

Answer 6

• makes the lens thinner or thicker

- made up of suspensory ligaments, which are connected to the lens and ciliary muscles (both sides of lens)

Question 7

iris

Answer 7

• colored part of eye

- 2 different muscles that contract and expand (size of pupil gets bigger and smaller)

Question 8

pupil

Answer 8

• hold controlled by iris
• if dark outside–> pupil gets bigger so max amount of light rays can enter
• if bright- pupil is smaller

Question 9

vitreous humor

Answer 9

• makes up posterior chamber or eye
• helps suspend lens in place
• structure for the eye
• transparent

Question 10

retina

Answer 10

• coats the entire back of the eyeball
• composed of photoreceptors
• tinted red (red eye effect)
• sends fibers through back of eye–> fibers form optic nerve

Question 11

optic nerve

Answer 11

• retina sends fibers here

- nerves go to the brain

Question 12

choroid

Answer 12

• network of blood vessels that nourish all the cells on retina and other parts of the eye
• black in color
• shiny in cats–> night vision

Question 13

fovea

Answer 13

• high concentration of cones
• allow you to see enriched detail
• at the center of the macula
• dimpled region from the retina- because photoreceptors are connected to other neurons that have axons that go to the optic nerve and exit the eye
• higher resolution of light fight at fovea because no axons there
• many rods outside of the fovea

Question 14

light

Answer 14

• physical stimulus, electromagnetic wave
• part of a large spectrum, light in the middle
• 400nm (violet)- 700 nm (red)

Question 15

photoreceptor

Answer 15

• takes physical stimulus (light) and turns into neural impulse
• rods and cones

Question 16

light ray to eye

Answer 16

• comes into eye and hits the back of the eye
• retina (lines back of eye) has rods and cones
• phototransduction cascade

Question 17

rod

Answer 17

• photoreceptor
• all over retina, take light and convert into neural impulse
• 120 million rods/retina
• optic disks with proteins embedded that absorb light–> phototransduction cascade
• protein in a rod called rhodopsin
• very sensitive to light (1000X more than cones)
• good for night vision
  SLOW recovery time
• found in periphery of the eye
• when light hits it, it turns off–> turns on bipolar cell–> turns on retinal ganglion cell–> goes into optic nerve and enters the brain

Question 18

cone

Answer 18

• photoreceptor (same internal structure as rod)
• protein in a cone called photopsin
• all over retina, take light and convert into neural impulse
• many cones centered in the fovea
• color vision
• 6-7 million cones/retina
  FAST recovery time
• red cones- sensitive to red light 60%
• green cones- sensitive to green light 30%
• blue cones- sensitive to blue light 10%

Question 19

phototransduction cascade

Answer 19

• set of things that happens as soon as light hits rod–> for us to recognize light
• turns rod from being on to off
• rod turns off when light hits it–> turns on bipolar cell–> turns on retinal ganglion cell–> to optic nerve–> neural impulse

Question 20

inside rod

Answer 20

• disks stacked on top of each other
• proteins interspersed throughout disks
• rhodopsin (protein) has subunits
• retinal (molecule)- when light hits, it causes retinal to change conformation from bent to straight (from cis to trans)
• -> causes rhodopsin molecule to change shape
• -> transducin (has alpha, beta, gamma) breaks away from rhodopsin and alpha subunit binds to phospodiesterase (PDE) protein
• -> takes cyclic GMP and converts to GMP
• sodium channels all over cell (rod)- cyclic GMP needs to be bound to channel for sodium to enter cell
• -> so when cyclic GMP is converted to GMP, sodium channels close–> cell hyperolerizes and TURNS OFF rod

Question 21

bipolar cell

Answer 21

• on center and off center
• when light turns on, rod turns off, bipolar cell is turned on
• then turns on retinal ganglion cell

Question 22

photoreceptor distribution in fovea

Answer 22

Rods
- 0 photoreceptors right at--> blind spot
- many in periphery
Cones
- very few in periphery
- many in fovea

Question 23

visual processing

Answer 23

• nasal side (close to nose)
• temporal side (close to temples)
• light coming from left visual field will hit nasal side of left eye
• light coming from left visual field will his temporal side of the right eye
  (vice versa)
• optic nerves converge at optic chiasm
• information sent via axons through back of the eye into the optic nerve–> crosses at optic chiasm
  ALL light that hits temporal side of the eyeball does NOT cross the optic chiasm
  ALL light that hits the nasal side of the eyeball DOES cross the optic chiasm
  –> this takes right visual field info to go to left side of brain, all info from left visual field goes to right side of the brain

Question 24

feature detection/parallel processing

Answer 24

• color- cones fire when see color
• form- parvo pathway
• motion- magno pathway
• -> get all information at the same time = parallel processing

Question 25

trichromatic theory of color vision

Answer 25

• cones have red, green, and blue cones
• light enters eye and if hits cone, cone activates and fires AP–> reaches brain that now know you are looking at that color

Question 26

parvo patheay

Answer 26

• used for stationary objects
• figuring out the shape of something
• spatial resolution- figuring out boundaries and details of object
• poor temporal resolution (motion)
• does not encode color

Question 27

magno pathway

Answer 27

• set of specialized cells that allow us to encode motion
• high temporal resolution
• poor spatial resolution
• does not encode color