eye

Question 1

cornea

Answer 1

-transparent refractive layer covering the front of the eye
-refracts light

Question 2

conjunctiva

Answer 2

-thin transparent membrane covering the sclera that helps lubricate the eye

Question 3

sclera

Answer 3

-tough white outer layer of connective tissue
-continuous with the cornea
-protects the eyeball from mechanical damage

Question 4

iris

Answer 4

-circular sheet of muscles which contains a pigment that gives the eye its colour
-the pair of antagonistic muscles, circular and radial muscles, controls the amount of light entering the eye

Question 5

pupil

Answer 5

-circular opening of the eye, which allows light to enter the eye

Question 6

eyelid

Answer 6

-protect cornea from mechanical damage
-blinking spreads tears and wipes off dust from the cornea

Question 7

eyelashes

Answer 7

-help shield eye from dust particles

Question 8

tear glands

Answer 8

-secrete tears via tear duct which,
-wash away dust particles
-keep cornea moist
-lubricate conjunctiva to reduce friction when eyelids move

Question 9

retina

Answer 9

-innermost layer of the eye
-contains photoreceptors, rods and cones
-nerve impulses generated are transmitted towards the brain along the sensory neurones in the optic nerve
-fovea of retina contains highest concentration of cones but no rods

Question 10

choroid

Answer 10

-middle layer of the eyeball
-pigmented black to absorb light, preventing internal reflection of light inside the eye
-contains blood vessels that provide oxygen and glucose to retina and remove metabolic waste from it

Question 11

lens

Answer 11

-refract and focus light on the retina
-due to the elastic and flexible nature of the lens
-the edge of the lens is attached to the ciliary body by suspensory ligaments. hence, its curvature can be altered by the action of the ciliary muscles to focus the image on the retina.

Question 12

blind spot

Answer 12

-there are no photoreceptors in the area of the retina where the optic nerve leaves the eye. hence, light falling onto the blind spot is not detected.

Question 13

optic nerve

Answer 13

-transmits nerve impulses from retina to the brain when photoreceptors in the retina are stimulated

Question 14

ciliary muscle

Answer 14

-contract or relax, to change the thickness of the lens

Question 15

suspensory ligament

Answer 15

-attaches the lens to the ciliary body

Question 16

aqueous and vitreous humour

Answer 16

-maintains the shape of the eyeball by providing an internal fluid pressure
-refracts light

Question 17

rectus

Answer 17

-attached on the outside of the eyeball
-controls movement of the eyeball

Question 18

how do we view objects?

Answer 18

-light rays reflected off an object entering the eye are refracted by the cornea and the lens
-the light rays stimulate the photoreceptors on the retina. nerve impulses generated are transmitted along the sensory neurone in the optic nerve to the brain.

Question 19

rods

Answer 19

-function in dim light, detecting shape and movement
-they are more sensitive to light than cones

Question 20

cones

Answer 20

-function in bright light, responsible for colour vision and are sensitive to different wavelengths of light
-three types of pigments in cones - blue, green and red

Question 21

image on the retina

Answer 21

-upside down
-laterally inverted
-real
-diminished/ smaller in size than the actual object

Question 22

focusing on a near object

Answer 22

-light rays from a near object are diverging
-they enter the eye and are refracted by the cornea through the pupil
-the lens needs to become thicker and more convex to bend light more sharply in order to focus it on the retina
-the ciliary muscles contract
-this causes the suspensory ligaments to slacken, reducing their pull on the lens
-the elastic lens becomes thicker and more convex
-photoreceptors on the retina are stimulated. nerve impulses are transmitted along sensory neurones in the optic nerve to the brain.
-the brain interprets the nerve impulses and the person sees the near object

Question 23

focusing on a distant object

Answer 23

-light rays from a distant object are nearly parallel
-they enter the eye and are refracted by the cornea through the pupil
-the lens do not need to be so thick as light does not need to be bent as much in order to focus it on the retina
-the ciliary muscles relax
-this causes the suspensory ligaments to become taut, which pull on the lens more
-the elastic lens is pulled into a thinner and less convex shape
-photoreceptors on the retina are stimulated. nerve impulses are transmitted along sensory neurones in the optic nerve to the brain.
-the brain interprets the nerve impulses and the person sees the distant object

Question 24

under low light intensity,

Answer 24

-circular muscle of iris relax
-radial muscle of iris contract
-pupils dilate, allowing more light to enter the eye for better vision

Question 25

under high light intensity,

Answer 25

-circular muscle of iris contract
-radial muscle of iris relax
-pupil constricts, to restrict light entry into the eye to prevent excessive light from damaging the retina