human response to enviro: sense organ= human eye

Question 1

what is the human eye responsible for

Answer 1

for sight

Question 2

what are the receptors that detect light called

Answer 2

photoreceptors

rods and cones (retina, back of eye)

Question 3

what do photoreceptors do

Answer 3

detect light stimulus and convert into nerve impulses which are sent to the brain (cerebrum) and is interpreted

Question 4

rods

Answer 4

receptors in the retina of the eye which are sensitive to dim lights and help to distinguish betw black and white

Question 5

cones

Answer 5

receptors in the retina of the eye which are sensitive to bright light and help distinguish between different colours

Question 6

pupil

Answer 6

central opening within the iris which allows light to enter

Question 7

binocular vision

Answer 7

vision using 2 eyes with overlapping fields of vision, allows good depth perception

important in developing good depth perception, in turn affects coordination and hand and eye skills

Question 8

name 3 structural adaptations of the eye that protect the eye

Answer 8

1- eyelids + eyelashes = protect eye from foreign objects

2- conjunctiva= protective, clear, thin mucous membrane, covers front eye
- contains pain receptors (blink reflex)

3- tear gland= above eyeball, secretes antiseptic tears, protect conjunctiva from bacteria and dehydration

Question 9

what are the 3 layers of the eye

Answer 9

1- outer fibrous layer (OSCor)

2- middle vascular layer (MiChoCILS)

3- inner light sensitive retina

also = yellow spot, blind spot, optic nerve

Question 10

what are the 2 parts of the outer fibrous layer (OSCor)

Answer 10

1- sclera
2- clear cornea

Question 11

what are the 5 parts of the middle vascular layer
(MiChoCILS)

Answer 11

1- choroid
2- ciliary body (accommodation)
3- iris (pupillary mechanism) note, pupil: circular opening in the iris
4- lens
5- suspensory ligaments (accommodation)

Question 12

what are the inner light sensitive retina parts and others

Answer 12

1- pigment layer
2- nerve tissue layer
3- yellow spot (highest concentration of cones, therefore clearest vision_)

4- blind spot (no rods + no cones, therefore no vision) part optic nerve leaves eye

5- optic nerve = conducts nerve impulses to cerebral cortex , then interpreted and gives rise to sensation of sight

Question 13

what are the 3 functionings of the eye

Answer 13

1- accommodation
2- pupillary mechanism
3- sensation of sight

Question 14

what is accomodation

Answer 14

the process of changing the shape of the lens to focus on near or distant objects

Question 15

describe near vision (accomodation, less than 6m from object) (6 parts )

C-C
S-S

Answer 15

1- Ciliary muscle Contracts
2- thus, suspensory muscle slackens (loosen)
3- thus, tension on lens decre

4- lens becomes convex (bulgey)
5- light rays refracted more (bend more )

6- clear image is focused on the retina (yellow spot)

Question 16

what is pupillary mechanism/ pupil reflex

Answer 16

process by which the diameter of the pupil (a circular opening in the iris) is altered to control the amount of light entering the eye

iris controls the amount of light entering the eye
iris has radial and circular muscles

Question 17

describe the pupillary mechanism/ pupil reflex in bright light (4 parts)

R-R
C-C

Answer 17

1- Radial muscle of iris Relax
2- Circular muscle of the iris Contracts (antagonistic muscles)

3- therefore pupil constricts (smaller)

4- less light enters the eye

Question 18

what are the 4 structures in the eye that refracts light rays that enter the eye

Answer 18

1- cornea
2- aqueous humour
3- lens
4- vitreous humour

Question 19

describe the process of sensation of light (5)

Answer 19

1- retina contains light sensitive photoreceptors (rods+ cones)

2- stimulated by incoming light rays

3- discharge nerve impulse

4- travel along optic nerve to cerebral cortex

5- sensation of sight arises

Question 20

what is shortsightedness

Answer 20

ability to see nearby objects but cant see distant objects clearly

when looking at distant objects, light rays focus in front of retina, causing blurred vision

Question 21

what are 3 possible causes of short sightedness

Answer 21

1- too long eyeball
2- cornea too curved for eyeball length
3- inability of lens to become less convex

Question 22

what is the treatment of short sighted ness

Answer 22

wear glasses with concave lenses

Question 23

what are 5 visual defects

Answer 23

1- short sightedness
2- long sightedness
3- astigmatism
4- cataracts

Question 24

what is long sightedness

Answer 24

ability to see distant objects but cant see nearby objects clearly

Question 25

name 3 possible causes of long sightedness

Answer 25

1- too short (rounded) eyeball
2- cornea less curved for eyeball length
3- inability of lens to become more convex

Question 26

what is the treatment for longsightedness

Answer 26

wear glasses with convex lenses

Question 27

what is astigmatism

Answer 27

when cornea or lens not equally rounded in all directions

light not focused evenly on retina

leads to : headaches, blurred vision, squinting of eyes

Question 28

treatment of astigmatism

Answer 28

1- glasses with prescription lenses
2- contact lenses
3- laser therapy

Question 29

what is cataracts

Answer 29

when clear transparent lens becomes cloudy and opaque

leads to blurred vision

Question 30

what is the treatment fir cataracts

Answer 30

surgery to replace the lens with synthetic lens