The Eye

Question 1

what are the photoreceptors in the eye sensitive to?

Answer 1

-light

Question 2

how is the eye given the correct intensity of light?

Answer 2

-through the structures in the eye that ensure the correct intensities of light are received by receptors in the retina

Question 3

look at diagram of the eye in book page 69 be able to draw it out

Question 4

what is the conjunctiva and what is its function?

Answer 4

-thin epithelial layer which moistens and lubricates the eye

Question 5

what is the sclera and what is its job?

Answer 5

-tough connective tissue covering the eye
-protects against damage

Question 6

what is the cornea and what is its job?

Answer 6

-transparent part of the sclera
-refracts light

Question 7

what is the aqueous humour and what is its job?

Answer 7

-watery fluid between the cornea and lens
-maintains shape of the front of the eye

Question 8

what is the iris and what is its job?

Answer 8

-muscular layer which contains both circular and radical muscle also contains a pigment that absorbs light
-adjusts size of pupil to control amount of light entering

Question 9

what is the pupil and what is its job?

Answer 9

-gap within the iris
-the area where light reaches the lens and enters the center of the eye

Question 10

what is the ciliary body and what is its job?

Answer 10

-contains a muscular ring and suspensory ligaments which holds the lens in place
-adjusts shape of the lens to focus light rays

Question 11

what are suspensory ligaments and what is its job?

Answer 11

-connects biliary body to the lens
-transfers tension so that the light can focus on distant objects

Question 12

what is the lens and what is its job?

Answer 12

-transparent and biconvex
-refracts light and focuses light rays

Question 13

what is the viteous humour and what is its job?

Answer 13

-jelly like material between the lens and the back of the eye
-maintains shape of the eye

Question 14

what is the retina and what is its job?

Answer 14

-inner layer of the eyeball which contains cones and rods
-initiate impulses associated with neurones

Question 15

what is the foeva and what is its job?

Answer 15

-region in the center of the retina which is rich in cones
-give clear daylight and colour vision

Question 16

what is the choroid and what is its job?

Answer 16

-layer of pigmented cells between retina and sclera
-contains blood vessels and prevents reflection at the back of the eye

Question 17

what is the optic nerve and what is its job?

Answer 17

-bundle of sensory nerve fibers
-transmits impulses from the retina to the brain

Question 18

what is the blind spot and what is its job?

Answer 18

-part of retina that is not sensitive to light

Question 19

what are the two functions of the eye?

Answer 19

-obtaining a focused image
-controlling the amount of light that enters the retina

Question 20

where does most refraction of light occur? where does some occur initially?

Answer 20

-most happens in the cornea however some refraction can occur when light initially hits the eye

Question 21

how is light focused on the retina?

Answer 21

-by adjusting the thickness of the lens

Question 22

how do the light rays arrive when the eyes are focusing on a distant object? what is the thickness of the lens like?

Answer 22

-light rays arrive parallel at the eye
- the lens is thin as little additional refraction has to occur for the light to focus on the retina

Question 23

how do the light rays arrive when the eyes are focusing on a close up object? what is the thickness of the lens like?

Answer 23

-light rays diverge from a close up object
-lens is thicker as further refraction must occur to focus light on the retina

Question 24

what is the ciliary muscle?

Answer 24

-a ring of muscle in the ciliary body which runs around the inside of the eyeball

Question 25

what do suspensory ligaments resemble?

Answer 25

-thin small pieces of nylon thread

Question 26

what happens if the ciliary body relaxes? what happens to the lens?

Answer 26

-tension on the walls of the eyeball is transferred to suspensory ligaments -meaning the ciliary body has a larger diameter and so the suspensory ligaments are pulled taut -this makes the lens thinner and so the eye has less refractive power

Question 27

what happens when if the ciliary body contracts and what happens to the lens?

Answer 27

-to make the lens fatter when a greater degree of refraction is required -ciliary muscle contracts -forms a tighter circle with a smaller diameter -suspensory ligaments are not pulled taut -less pressure on the lens so the lens is at its thicker normal shape

Question 28

what is the definition of accommodation?

Answer 28

-the adjustment of lens thickness to ensure that light rays are focused on the retina -irrespective of the angle of light reaching the eye

Question 29

look at diagram on page 72

Question 30

what are the two things that prevents an image being formed? (types of light intensites)

Answer 30

-too little or too much light prevents an image being formed

Question 31

what also can happen due to too high a light intensity?

Answer 31

-damage the sensitive light receptors

Question 32

what size is the pupil in low light intensities? why?

Answer 32

-large -allow as much light as possible to enter the eye to ensure there is enough light for an image to be formed -to stimulate the photoreceptors

Question 33

what size is the pupil in bright light and why?

Answer 33

-pupil is reduced to a smaller size to restrict the amount of light entering

Question 34

how is the pupils size changed?

Answer 34

-due to the iris contracting or relaxing

Question 35

what are the two types of muscle that the iris contains?

Answer 35

-circular and radical

Question 36

what happens to the muscles in the iris in low light intensities?

Answer 36

-the radical muscles contract and the circular muscles relax which makes the pupil larger

Question 37

what happens to the muscles in the iris in bright light?

Answer 37

-the circular muscles contract and the radical muscles relax which makes the pupil smaller