Section 12.2 - Photoreception (Eye)

Question 1

What is the Sclera?

Answer 1

The outer white, tough fibrous layer of the eyeball.

Question 2

Function of the Sclera

Answer 2

• maintains the eye shape
• acts as a protective layer

Question 3

What is the Cornea?

Answer 3

At the front, the sclera becomes clear and is known as the cornea.

Question 4

Function of the Cornea

Answer 4

• It bends light towards the pupil, light enter eye.
• focuses light through bending or refraction

-protect front of eye

Question 5

What is the Aqueous Humour?

Answer 5

Clear, watery fluid located behind the cornea.

Question 6

Function of the Aquarius Humour?

Answer 6

• The fluid maintains the shape of the cornea, and provides oxygen and nutrients for surrounding cells.

Question 7

What is the Choroid?

Answer 7

The middle layer of the eyeball, it’s thin and dark.

Question 8

Function of the Choroid

Answer 8

• absorbs stray light rays that are not detected by photoreceptors.
• contains blood vessels that supply the retina.

Question 9

Iris

Answer 9

Toward the front the choroid forms the iris.

Question 10

Function of the Iris

Answer 10

Regulates the amount of light that enters the eye.
- adjusts size of pupil based on light conditions (adaptation).

Question 11

What is the Pupil?

Answer 11

The Iris contains the pupil

Question 12

Function of the pupil?

Answer 12

• opening for light to pass through.

Question 13

What is the Retina?

Answer 13

Internal layer of the eye, forms the back of the eye.

Question 14

What does the Retina contain?

Answer 14

Photoreceptor cells that capture light and generate neural messages.

Question 15

Examples of photoreceptors

Answer 15

Rods and Cones in the retina

Question 16

Rods

Answer 16

• Detect black, white, grey
• More sensitive than cones
• Dim light, night vision

Question 17

Where are the rods SPECIFICALLY located?

Answer 17

They’re located around the edges of the retina, provide peripheral vision.

Question 18

Cones

Answer 18

• Colour vision: red, blue, green.
• sensitive to different colours

Question 19

Where are the Cones SPECIFICALLY located

Answer 19

• packed at centre of retina, in an area called FOVEA CENTRALIS.

Question 20

What are the Ciliary Muscles?

Answer 20

• behind the Iris
• the choroid thickens and forms the ciliary muscles, which surround the lens.

Question 21

Function of the Ciliary Muscles

Answer 21

Changes shape of the lens in order to focus.

Question 22

Function of the Lens

Answer 22

Bend and Focus light rays on the retina, specifically onto the fovea centralis.

Question 23

Optic Nerve

Answer 23

The rods and cones send sensory impulses to the brain via the optic nerve.

Question 24

What’s is the Vitreous Humour

Answer 24

Fluid that fills the eyeball, surrounded by retina.

Question 25

Function of the Vitreous Humour

Answer 25

• Jelly-like fluid that maintains the shape of the eyeball.
• Allows light to pass through inner eye

Question 26

Blind Spot

Answer 26

Region at the back of the inner eye, where no photoreceptors are found.

Question 27

Suspensory Ligaments

Answer 27

Strings that attach the ciliary muscles to the lens.

Question 28

What does the Cornea look like?

Answer 28

Transparent layer, allows light to pass through.

Question 29

What does the Sclera look like?

Answer 29

The sclera is the opaque, visible white portion of one’s eye.

Question 30

Accommodation

Answer 30

Is adjustments to the shape of the lens.

Question 31

What controls the lens shape?

Answer 31

• the ciliary muscles

Question 32

How does the eye accommodate to see distant objects?

Answer 32

• ciliary muscles relax,
• sensory ligaments stretched
• lens flatter
• more concave

Question 33

How does the eye accommodate to see closer objects?

Answer 33

• lens becomes round, fatter, more convex.
• ciliary muscles contract
  -suspensory ligaments relax.

Question 34

Cataracts

Answer 34

Occur when a lens becomes cloudy, preventing light from passing through to the retina.

• most likely occur as people age

Question 35

Astigmatism

Answer 35

Occurs when the surface of the lens or cornea does not have a smooth curve.

• vision is blurred

Question 36

Glaucoma

Answer 36

Damage to the retina caused by excessive pressure from build up of aqueous humour in eye,

• causes blindness.

Question 37

Nearsightedness (myopia)

Answer 37

Unable to see distant objects.

• eyeball too long, lens too round.
• image focused in front of retina
• corrected by using concave lens

Question 38

Farsightedness (hyperopia)

Answer 38

Unable to see near object.

• eyeball too short, lens too flat.
• focused behind retina
• corrected with convex lens.

Question 39

Pathway of Light

Answer 39

Cornea,
Pupil,
lens,
vitreous humour,
retina,
optic nerve,
optic chiasma,
and finally to visual cortex in occipital love.
CPLVROV

Question 40

What do rods and cones contain?

Answer 40

Photopigments - absorb light

Question 41

What are photopigments composed of?

Answer 41

A membrane protein called OPSIN, and the light absorbing chromosphere retinal.

Question 42

What’s the photo pigment in rods called?

Answer 42

Rhodopsin

Question 43

What happens when light strikes a photopigment?

Answer 43

The structure of retina is altered and becomes partially detached from the opsin protein.

OPSIN then undergoes a conformational change leading to a series of biochemical reactions

Question 44

When are photoreceptor Na+ channels open?

Answer 44

In the dark.

Neurotransmitter (glutamate) is released from photoreceptors in the dark.

Glutamate = inhibitory neurotransmitter
(No action potential)