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Biology > The eye > Flashcards

The eye Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

definiton of sense organ

A

type of receptor that receives stimuli from envo and inform the body of any changes in envo

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2
Q

Where can you find your eye? & how is it connected to your skull?

A

lies in a hole in the skull called the orbit-> attached to skull by rectus muscles which control eye movement

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3
Q

Name the different parts of the outer surface of the eye(9)

A 
iris
pupil
cornea
conjunctiva
nictitating membrane
sclera
eyelids
eyelashes
tear gland
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4
Q

functions of iris

A

it is a circular sheet of muscles-> circular n radial muscles( 2 sets of involuntary muscles)
control the amt of light entering the eye
contain a pigment which gives your eye colour

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5
Q

pupil

A

the hole/opening in the middle of your eye, dilates and constricts to control the amt of light entering your eye

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6
Q
  1. cornea
A

a dome-shaped transparent layer continuous w sclera, main refractor of light

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7
Q

tear glands

A

gland lying at the corner of the upper eyelid
tears are produced, to wash away dust particles, keep cornea moist for atmospheric oxygen to dissolve and to lubricate the conjunctiva->helping to reduce friction when the eyelids move

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8
Q

conjunctiva

A

thin transparent membrane covering the sclera
mucous membrane
secretes mucous to moisten eye
continuous w skin of eyelid

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9
Q

sclera

A

the tough white surface covering the eyeball
continuous w cornea
protects the eyeball from mechanical damage

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10
Q

eyelids

A

protects the cornea from mechanical damage
can be partly closed-> squinting which prevents excessive light frm entering the eye and damaging the light-sensitive tissues(retina) inside
blinking-> spreads tears ovr the cornea & conjunctiva-> wipes dust particles off the cornea

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11
Q

eyelashes

A

prevents dust particles frm rching your eye

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12
Q

Name the parts of the outermost layer of the eye(2):

A

cornea and sclera

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13
Q

name the parts of the middle layer of the eye(6):

A 
choroid
suspensory ligaments
lens
aqueous chamber
vitreous chamber
ciliary body
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14
Q

name the parts of the inner layer of the eye(4):

A

blind spot
fovea/yellow spot
retina
optic nerve

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15
Q

choroid

A

between retina and sclera(middle layer of eyeball)
pigmented black to facilitate inter reflection
has blood vessels which transport necessary oxygen to it while transporting metabollic waste products away from it

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16
Q

choroid

A

between retina and sclera(middle layer of eyeball)
2 functions: pigmented black to prevent inter reflection of black
has blood vessels which transport necessary oxygen and nutrients to it while transporting metabolic waste products away from it

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17
Q

ciliary body

A

thickened region at the front end of the choroid, contains ciliary muscles which control the curvature/thickness of the lens

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18
Q

suspensory ligaments

A

connective tissue that attaches the edge of the lens to the ciliary body

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19
Q

vitreous chamber

A

the space behind the lens filled with vitreous humour a transparent, jelly-like substance that keeps the eyeball firm and refracts light onto the retina

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20
Q

aqueous chamber

A

space between lens and cornea, filled with aqueous humour a transparent watery fluid that keeps the front of the eyeball firm and helps to refract light into pupil

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21
Q

lens

A

is a transparent, circular and biconvex structure that is elastic and can change shape and thickness in order to focus light onto retina

22
Q

blind spot

A

region where the optic nerve leaves the eye, spot on the retina with no rods or cones therefore it is not sensitive to light

23
Q

fovea/blind spot

A

is a small yellow depression in the retina
situated directly behind the lens
& is whr images r normally formed
contains the greatest concentration of cones but no rods, thus allowing a person detailed colour vision in bright light

24
Q

retina

A

innermost layer of the eyeball
light-sensitive layer on which images are formed
has light-sensitive cells aka photoreceptors which consists of rods and cones, rods-> see black and white in dim light, cones-> see colours in bright light
photoreceptors r connected to the nerve endings frm the optic nerve

25
Q

optic nerve

A

transmit nerve impulses to the brain whn the photoreceptors in the retina r stimulated

26
Q

What does photo receptors consist of?

A

rods n cones

27
Q

What are these things that make up photoreceptors connected to?

A

connected to nerve endings frm the optic nerve

28
Q

cones enable us to see in what intensity of light?

A

bright light

29
Q

what are the 3 colour of cones? And what can you say about them?

A

red, blue and green

each cone contains a diff pigment which absorbs light of diff wavelengths

30
Q

what do the cones achieve together?

A

help us to see a wide variety of colours

31
Q

it does not work well in what type of light?

A

dim light

32
Q

it is most sensitive to what intensity of light?

A

high intensity

33
Q

are rods more sensitive to light or cones?

A

rods r more sensitive to light than cones

34
Q

rods is most sensitive to what intensity of light? And what colour do you see in?

A

dim light, black and white

35
Q

rods are sensitive to light of low intensity(dim light) bcos of?

A

thy contain a pigment called visual purple

36
Q

what happens to visual purple in bright light?

A

it gets bleached

37
Q

what will happen if one has vitamin A deficiency?

A

visual purple has to b reformed for a person to see in the dark which takes some time & requires vitamin A so a person deficient in vitamin A may b unable to see in dim light as thy r unable to reform their visual purple n thy r said to suffer frm night-blindness

38
Q

what happens once photoreceptors are stimulated?

A

nerve impulses r initiated n transmitted to sensor neurones in optic nerves

39
Q

pupil reflex

A

in order for a person to see clearly, only the right amt of light shld enter their eye

40
Q

size of pupil

A

controlled by 2 sets of involuntary muscles in the iris, circular n radial muscles-> antagonistic, whn one side contracts, the othr relaxes n vice versa

41
Q

in bright light

A

the circular muscles of iris contracts while the radial muscles of iris relaxes and so the pupil bcomes smaller/contracts-> reduces amt of light entering the eye

42
Q

in dim light

A

the circular muscles of iris relaxes while the radial muscles of iris contracts and so the pupil hcomes bigger-> increase amt of light entering the eye

43
Q

explain pupil reflex in the form of nervous system:

A

the stimulus is the change in light intensity
receptor: photoreceptor in retina
CNS: brain processes nerve impulses
effector: muscles tht make up iris(antagonistic-> involuntary radial & circular msucles)
response: change in the size of pupil to control the amt of light entering they eye n also the eyelids tht will cm tgthr to screen off part of the light(squinting), if decreasing the size of pupil is not enough bcos the light is too bright
this will prvent excessuve light frm entering the eye n damaging the retina

44
Q

reflex arc:

A
  1. the light rays enter the eye
  2. photoreceptors in retina r stimulated
  3. nerve transmitted to sensory neurone in optic nerve
  4. then to relay neurone in brain
  5. go to brain
  6. then to motor neurone
  7. then to iris(effector)
45
Q

how do we see?

A
  1. light rays r refracted thru the cornea and aqueous humour onto lens
  2. lens cause further refraction
  3. rays r brought to a focus on retina
  4. image on retina stimulates either rods r cones depending on light intensity
  5. image formed on retina is: -> upside down & laterally inverted
    the nerve impulses that r produced whn light falls on rods n cones r transmitted via optic nerve to the brain which interprets these impulses so tht we see the obj the right way up, front to bck n in the right size.
46
Q

defintion of focusing/accomodation reflex

A

is the adjustment of the lens of the eye so tht clear images of objs at diff distances r formed on the retina
it is neccesary so tht objs at diff disrances can b seen clearly and the thickness of the lens are adjusted to allow the light rays to b focused on the retina

47
Q

focusing on distant objs: (more than 7m away is considered a distant obj)

A

light rays reflecting off the obj r almost parallel to ech othr whn thy rch the eye-> refracted thru the cornea n aq humour into pupil-> lens need to b thinner as only a lil refraction is required
steps:
1. parallel light rays frm distant obj enter the eye
2. (receptors: sensory neurone is the photoreceptors, send nerve impulse to brain to relay neurone to motor neurone to effector which is the ciliary muscles, causing it to relax) ciliary muscles relax-> pulling on suspensory ligaments
3. suspensory ligaments bcome taut, pulling on the edge of the lens
4. so the lens bcome thinner
5. the focal length also increases
6. light rays frm distant obj r sharply focused on retina
7. photoreceptors r stimulated
8. nerve impulses r produced
9. transmitted via optic nerve to brain
10. brain interprets impulses
11. person sees distant obj

48
Q

focusing on near objs

A

divergent light rays reflect off near objs n it is refracted thru the cornea n aq humour into pupil since rays rching the eye r diverging so the lens hv to b more convex to bend the light rays more
steps:
1. diverging light rays frm near obj enters the eye
2. ciliary muscles contract, relaxing their pull on suspensory ligaments( this is why the eye bcomes more tired aft looking @ a nearby obj)
3. suspensory ligaments slacken, relaxing their pull on the lens
4. the lens being elastic becomes thinner
5. bcome more convex so the focal length decreases
6. light rays frm near obj r sharply focused on retina
7. photoreceptors r stimulated
8. nerve impulses r produced by photoreceptors
9. transmitted via optic nerve to brain
10. brain interprets impulses
11. person sees near obj

49
Q

short-sightedness

A

caused by the eyeball being ELONGATED so tht the dist btwn the lens n the retina is too great-> can b corrected by placing a concave lens in front of the eyes

50
Q

long-sightedness

A

bcos the lens focuses the sharpest image behind the retina instead of on it, often age-related n due to a loss of elasticity of lens-> can b corrected by placing a convex lens in front of the eye

Biology (5 decks)

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