Human Eye

Question 1

what does the sensory input of the eye involve?

Answer 1

• light detecting cells
• conduction of signals from the sensory receptors to the integration centre

Question 2

what are the light detecting cells found in the retina?

Answer 2

rods and cones

Question 3

what is integration?

Answer 3

• process where information from the environmental stimulation of the sensory receptors is interpreted
• associated with appropriate responses of the body
• carried out in the central nervous system CNS

Question 4

what is motor output?

Answer 4

• the conduction of signals from the central nervous system
• conduction of signals to the effectors
• carry out the body’s responses to the stimulus

Question 5

where does the tear sac empty into?

Answer 5

nasal cavity

Question 6

structure of the conjunctiva?

Answer 6

• thin mucous transparent membrane
• covers the sclera in front
• continuous with the skin of the eyelids

Question 7

function of the conjunctiva?

Answer 7

• protects the cornea at the front of the eyeball against friction
• keeps the eyeball moist

Question 8

structure of the cornea?

Answer 8

• anterior end of the sclera that forms a small bulge in front of the eye
• transparent portion of the sclera

Question 9

function of the cornea?

Answer 9

• allows light to pass through to reach the retina
• refracts light into the pupil

Question 10

structure and function of the sclera?

Answer 10

tough white outer layer of the eyeball that protects it against mechanical injury

Question 11

structure and function of the choroid?

Answer 11

• contains blood vessels to supply the retina with oxygen and nutrients
• pigmented black to prevent internal reflection of light

Question 12

structure and function of the retina?

Answer 12

innermost layer that contains photoreceptors that detect stimuli

Question 13

function of cones?

Answer 13

concerned with colour vision in bright light

Question 14

function of rods?

Answer 14

concerned with vision in dim light

Question 15

function of the optic nerve?

Answer 15

transmits nerve impulses from the photoreceptors to the brain

Question 16

structure of the iris?

Answer 16

• anterior end of the choroid
• consists of the circular and radial muscles

Question 17

function of the iris?

Answer 17

• controls the size of the pupil, and hence the amount of light that enters the eye
• contains pigments to give the eye its colour

Question 18

are the circular and radial muscles voluntary or involuntary?

Answer 18

involuntary

Question 19

what is the pupil?

Answer 19

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

Question 20

structure of the lens?

Answer 20

• transparent biconvex structure
• elastic

Question 21

function of the lens?

Answer 21

focuses light rays by changing thickness onto retina

Question 22

function of the suspensory ligaments?

Answer 22

holds the lens in position by attaching the lens to the ciliary body

Question 23

function of the ciliary body?

Answer 23

• supports the lens
• contains muscles which control the curvature of the lens

Question 24

structure of the vitreous humour?

Answer 24

• transparent
• jelly-like

Question 25

function of the vitreous humour?

Answer 25

- supports the lens - refracts light rays onto the retina - keeps the eyeball firm

Question 26

structure of the aqueous humour?

Answer 26

- transparent - watery fluid

Question 27

function of the aqueous humour?

Answer 27

- refracts light onto the retina - keeps the eyeball firm - maintains the shape of the anterior chamber of the eyeball

Question 28

what does the fovea contain?

Answer 28

densely-packed cones

Question 29

function of the fovea?

Answer 29

- part of the retina most sensitive to light - has acute colour vision in bright light

Question 30

what is the blind spot?

Answer 30

- found immediately over the optic nerve - no photoreceptor cells

Question 31

what are the difference between the rods and cones?

Answer 31

- sensitivity to light - ability to distinguish colours - concentration in what part of the retina - images provided

Question 32

what are the three types of cones?

Answer 32

- red cones - blue cones - green cones - the cones come together to enable a spectrum of colours to be seen

Question 33

how do we see images in the eye?

Answer 33

1. refracted light rays from the object enter the eye through the pupil 2. light rays are refracted by the cornea, aqueous and vitreous humour, and the lens to focus on the retina 3. the lens make fine bending adjustments to focus the rays 4. an image formed on the retina stimulates the photoreceptors 5. nerve impulses generated are transmitted to the brain via optic nerve 6. the brain interprets the impulses to see the object the right way

Question 34

properties of the image formed on the retina

Answer 34

- inverted - upside down - back to front - inverted - diminished

Question 35

what is the pupil reflex?

Answer 35

an immediate involuntary change in the diameter of the pupil in response to the intensity of light that falls on the photoreceptor cells

Question 36

what happens during high light intensity?

Answer 36

1. circular muscles of the iris contract 2. radial muscles relax 3. pupil size constricts 4. reduces the amount of light that enters the eye, preventing damage to the rods and cones

Question 37

what happens during low light intensity?

Answer 37

1. circular muscles of the iris relax 2. radial muscles contract 3. pupil size dilates 4. allows as much light as possible to enter the eye, for us to see more clearly

Question 38

what is focusing?

Answer 38

the adjustments of the lens of the eye so clear images at different distances can be formed on the retina?

Question 39

what happens when we focus at a distant object?

Answer 39

1. light rays reflecting off the object are almost parallel when they enter the eye 2. ciliary muscles relax 3. suspensory ligaments are pulled taut 4. lens become thinner and less convex and refractive for image to be focused on the retina 5. an image formed on the retina stimulates the photoreceptors 6. nerve impulses generated are transmitted to the brain via optic nerve 7. the brain interprets the impulses to see the object the right way

Question 40

what happens when we focus at a near object?

Answer 40

1. light rays reflecting off the object are divergent when they enter the eye 2. ciliary muscles contract 3. suspensory ligaments slacken 4. lens become thicker and more convex and refractive for image to be focused on the retina 5. an image formed on the retina stimulates the photoreceptors 6. nerve impulses generated are transmitted to the brain via optic nerve 7. the brain interprets the impulses to see the object the right way