the eye

Question 1

func of the eyelid

Answer 1

protection against mechanical damage
squinting prevents excessive entry of light
blinking spreads tears and removes irritants

Question 2

func of tear glands

Answer 2

secrete tears to remove irritants

lubricate conjunctiva and moisturise the eye

Question 3

func of eyelash

Answer 3

shields the eye from irritants

Question 4

func of the iris

Answer 4

pigmented layer of muscular tissue

consists of radial and circular muscles which control the diameter of the pupil and light which enters the eye

Question 5

func of pupil

Answer 5

hole in the centre of the iris which allows light to enter the eye

Question 6

func of conjunctiva

Answer 6

mucus membrane covering sclera

Question 7

func of cornea

Answer 7

refracts light rays (has the most refractive power)

Question 8

func of sclera

Answer 8

protects against mechanical injury, allows attachment of eye muscles to enable movement, maintains shape of eyeball

Question 9

func of choroid

Answer 9

black pigmented layer which prevents internal refraction of light
rich in blood vessels to transport o2, nutrients, waste products

Question 10

func of retina

Answer 10

innermost light-sensitive layer on which images are formed

contains photoreceptors, connected by nerve fibers from optic nerve

Question 11

func of fovea

Answer 11

pit in retina where images are focused
contains cones but no rods
permits detailed coloured vision

Question 12

func of blind spot

Answer 12

point in retina where optic nerve exits eye

no photoreceptors, insensitive to light

Question 13

func of optic nerve

Answer 13

transmit nerve impulses from photoreceptors to brain

Question 14

func of vitreous humour

Answer 14

transparent jelly like substance
maintains shape of the eye
refracts light onto retina

Question 15

func of lens

Answer 15

shape/thickness can be changed to refract/focus light onto the retina

Question 16

func of ciliary body

Answer 16

contains ciliary muscles that control the curvature and thickness of lens

Question 17

func of suspensory ligament

Answer 17

attaches lens to ciliary body

Question 18

func of aqueous humour

Answer 18

clear watery fluid that supplies nutrients to cornea and lens
maintains convex shape of cornea
refracts light into pupil

Question 19

rods vs cones

Answer 19

provide b&w vision vs coloured vision
dim light vs bright light
found in places other than fovea vs conc at fovea
peripheral vision vs fine details (respond quickly and able to perceive rapidly changing images)
light sensors vs colour sensors

Question 20

func rhodopsin in rods

Answer 20

allows sensitivity to light

bleached under bright light, regenerated in absence of light

Question 21

pupil reflex (bright)

Answer 21

circ musc contract
radial musc relax
pupil diameter decr
amount of light entering decr

Question 22

pupil reflex (dim)

Answer 22

circ musc relax
radial musc contract
pupil diameter incr
amount of light entering incr

Question 23

reflex arc (pupil reflex)

Answer 23

1. incr/decr in light intensity was detected by photoreceptors in the eyes
2. nerve impulses generated, carried by sensory neurone in optic nerve, passed over a synapse to a relay neurone in the brain
3. relay neurone would pass the impulse to an outgoing motor neurone across another synapse
4. the motor neurone would bring the impulse to the motor end plates in the circular and radial muscles in the iris, causing them to contract/relax respectively
5. the pupil constricts/dilates, incr/decr amount of light entering to fall on the fovea of the retina

Question 24

focusing/accommodation: distant

Answer 24

ciliary muscles: relax
suspensory ligaments: taut
lens: thinner, less convex
focal length: incr

Question 25

focusing/accommodation: near

Answer 25

ciliary muscles: contract
suspensory ligaments: slacken
lens: thicker, more convex
focal length: decr

Question 26

properties of images focused on the retina

Answer 26

vert inverted, laterally inverted, diminished

Question 27

reflex arc (focusing)

Answer 27

1. inverted image is formed on the retina
2. photoreceptors are stimed
3. nerve impulses generated are transmitted through the optic nerve to the optic centre of the brain
4. brain interprets the info and forms an upright image