problem 1 - the eye

Question 1

The pupil

Answer 1

• controls intensity of the light entering the eye
• controlled by the contraction of the iris

Question 2

the cornea

Answer 2

• focuses the light that enters the eye
• accounts for 80% of the eye’s focusing power - but its fixed in place, so can’t adjust its focus (like a glasses lense)
• transparent membrane

Question 3

the lens

Answer 3

• works with cornea to adjust the light
• supplies the remaining 20% of the eyes focusing power - can adjust (ciliary muscles and zonule fibers) its shape to focus on stimuli located in different distances

diff between iris and lens:
iris is responsible for the amount of light and is adjusted to the light in the room, whereas the lens is focused on the objects and their shapes

Question 4

the iris

Answer 4

• colored part, a small donut-shaped muscle with an opening in the middle (light enters)

Intense light = contraction (constricts) = pupil smaller

Dim light = relaxation (dilates) = pupil larger

Question 5

the lens: accomodation

Answer 5

ciliary muscles at the front of the eye tighten and increase the curvature of the lens so that it gets thicker

→ the curvature bends the light rays, which pull the focus point back to retina (image becomes sharp)

Question 6

the lens: near point

Answer 6

limit of accommodation → distance at which your lens can no longer adjust to bring close objects into focus

Question 7

the 3 membranes: sclera/fibrous tunic

Answer 7

tough, protective covering (the white of our eye) with transparent cornea

Question 8

the 3 membranes: choroid/vascular tunic

Answer 8

• lines the interior of sclera
• contains most of the blood vessels (supply the eye with oxygen and nutrients)

Question 9

the 3 membranes: retina

Answer 9

made up of neurons including the receptors that convert the light entering the eye into neural signals

Question 10

the 3 chambers: anterior chamber

Answer 10

• between cornea and iris, filled with clear thin fluid called aqueous humor
• contains nutrients for the eye & helps to keep pressure

Question 11

the 3 chambers: posterior chamber

Answer 11

between iris and lens, filled with clear thin fluid called aqueous humor

Question 12

the 3 chambers: vitreous chamber

Answer 12

• main interior portion of the eye
• filled with vitreous humor: a clear more gel-like fluid - helps maintain shape of the eye

Question 13

intraocular pressure

Answer 13

the pressure of fluids in the chambers must be > than air pressure (to prevent collapsing of the eyes)

Question 14

optic nerve

Answer 14

brings the light info to the brain from the eye through electrical impulses

Question 15

photoreceptors in the retina: rods

Answer 15

• provide black and white vision in dim light
• rods are more sensitive to light than cones
• there are many more rods than cones in the retina (120m rods and 6m cones)

Question 16

photoreceptors in the retina: cones

Answer 16

provide high-acuity color vision in bright light
* S-cones: most sensitive to short wavelengths of light
* M-cones: most sensitive to medium wavelengths of light
* L-cones: most sensitive to longer wavelengths of light
* Cones are more responsible for detailed vision - responsible for color perception

Question 17

horizontal cells (retina)

Answer 17

• transfer info to other horizontal cells + to the cones and rods
• determine how much other cells around them will be activated or not activated (related to lateral inhibition)

Question 18

bipolar cells (retina)

Answer 18

receive signals from the rods and the cones to transfer it to the other cells, the amacrine and the ganglion cells

Question 19

amacrine & ganglion cells (retina)

Answer 19

send action potential to the optic nerves which goes further to the brain

Question 20

myopia / near-sightedness

Answer 20

inability to see distant objects clearly
* myopic eye brings the rays of light into focus in front of the retina = image reaching the retina is blurry

refractive myopia: cornea and/or lens bends the light too much

axial myopia: eyeball is too long

Question 21

hyperopia / farsightedness

Answer 21

trouble seeing nearby objects
* light into focus behind the retina = image reaching the retina is blurry
* can be caused by eye being too small

Question 22

astigmatism

Answer 22

blurred distance and near vision
* caused by cornea having an irregular shape - it is more oblong than round

Question 23

presbyopia

Answer 23

the distance of the near point increases as a person gets older
* lens gets harder & muscles get weaker = cannot accommodate as easily

Question 24

retinitis pigmentosa

Answer 24

degeneration of the retina (hereditary) - first attacks the peripheral rod receptors = poor vision of the peripheral field

In severe cases, foveal cone receptors also attacked = complete blindness

Question 25

macular degeneration

Answer 25

fovea and area around it destroyed = blind spot in central vision
* when the person looks at something, they lose sight of it (most common in elderly)
* peripheral vision is still intact

Question 26

the blind spot

Answer 26

place where the optic nerve leaves the eye = no receptors
* everyone has one
* Is located off to the side of our visual field, where objects are not in sharp focus
* We don’t see the blind spot because the brain “fills it in”

Question 27

detached retina

Answer 27

• Usually caused by accidents
• Vision is disturbed because you cannot process the light anymore
• No connection between photoreceptors and the brain

Question 28

glaucoma

Answer 28

a group of eye diseases that can cause vision loss and blindness by damaging the optic nerve due to a lot of pressure
* The pressure comes from a build up of fluid in the anterior chamber

Question 29

lateral inhibition

Answer 29

inhibition transmitted across the retina - the phenomenon in which a neuron’s response to a stimulus is inhibited by the excitation of a neighboring neuron
* Influences how one perceives light and dark - causes you to be less sensitive to light

Question 30

simultaneous contrast

Answer 30

occurs when our perception of the brightness or color of one area is affected by the presence of an adjacent or surrounding area

Question 31

hypothesis of belongingness (white’s illusion)

Answer 31

area’s appearance is influenced by the part of the surroundings to which the area appears to belong
* explains white’s illusion where lateral inhibition cannot