Lecture 21

Question 1

The ____ divides the interior of the eyeball into two chambers

Answer 1

lens

Question 2

What are the 2 chambers of the eye?

Answer 2

• Anterior/ Aqueous Chamber
• Posterior/ Vitreous Chamber

Question 3

Where is the cornea located?

Answer 3

it is the transparent bulge at the front of the eye, continuous with the white of the eye, or sclera — the outer wall of the eyeball

Question 4

What helps maintain the eyeball’s shape?

Answer 4

Behind is the vitreous chamber, filled with the vitreous body, a clear jelly

Question 5

The role of the Cornea and Lens

Answer 5

focus light on the retina, the inner lining of the eye that contains the photoreceptors.

Question 6

Where does light pass from the cornea to the lens?

Answer 6

Through a hole in the iris (the pupil)

Question 7

In which order does light travel into the eye?

Answer 7

Cornea, pupil, iris, lens, retina

Question 8

What is the Sclera?

Answer 8

the white outer coating of the eye

Question 9

What is the role of the pupil?

Answer 9

• controls depth of field (the focus)
• helps to focus light

Question 10

What controls pupil dilation?

Answer 10

• parasympathetic cells and sympathetic cells through the pupillary constrictor muscle and the radial pupillary dilator muscle of the iris

Question 11

What happens when the eye is exposed to bright light?

Answer 11

• parasympathetic signals from the brain contract the pupillary constrictor muscle - - shrinking the pupil

Question 12

What happens when the eye is exposed to the dark?

Answer 12

• sympathetic signals contract the radial pupillary dilator muscle of the iris
• dilating the pupil

Question 13

What happens to our depth of field when the pupil is tightly constricted/ not dilated?

Answer 13

we have full depth of field, i.e. everything we see is equally in focus.

Question 14

What happens to our depth of field when the pupil is dilated?

Answer 14

we have a shallow depth of field, i.e. only objects near one specific distance are in focus

Question 15

How can we get a retinal image that is both bright and in focus?

Answer 15

By using refraction.

Question 16

Refractive index

Answer 16

The ratio of the speed of light in a vacuum to its speed in a specific medium

Question 17

The higher the refractive index the _______ the light travels

Answer 17

slower

Question 18

What are our corneas made of?

Answer 18

clear collagen

Question 19

Why does clear collagen allow for strong bending of light/ refraction?

Answer 19

because there is a big difference between the refractive indices of air and collagen

Question 20

The cornea is responsible for ____ of the eye’s refraction, and the lens for ____

Answer 20

2/3
1/3.

Question 21

How can the lens adjust the focus of light?

Answer 21

through change in shape

Question 22

Why is refraction in water weak?

Answer 22

the refractive indices of collagen and water are similar

Question 23

What is the lens?

Answer 23

It is a mesh of long cells without nuclei, packed with clear proteins called crystallins, and “zippered” together in concentric layers for flexibility

Question 24

What makes up the lens?

Answer 24

clear cells and have no blood supply, but absorbs nutrients from the aqueous humor.

Question 25

A convex lens

Answer 25

is fatter in the middle and thinner at the edges. It makes light rays converge to a focal point.
- ie: magnifying glass

Question 26

Concave lenses

Answer 26

are thinner in the middle and fatter at the edges. They disperse light
- Ie: certain spectacles

Question 27

How is the angle of incidence formed?

Answer 27

The angle depends on the shape of the lens and the direction of the light ray; e.g. in the simplest case, if a ray strikes the lens at right angles then it doesn’t bend at all.

Question 28

What angle does refraction depend on?

Answer 28

the angle of incidence

Question 29

4 results of the Parasympathetic nerve signals

Answer 29

• contract the ring-shaped, smooth ciliary muscle
• reduces tension in the zonules
• making the lens rounder, so light rays bend more
• focal point moves forward.

Question 30

2 results of Sympathetic signals

Answer 30

• relax the ciliary muscle making the lens flatter
• allows for far vision

Question 31

What is hyperopia?

Answer 31

farsightedness
- the focal point falls behind the retina
-

Question 32

What is myopia

Answer 32

nearsightedness
- the focal point falls in front of the retina
- the lens is bending light rays too much

Question 33

How is hyperopia treated?

Answer 33

a convex lens in placed in front of the light to help bend light rays more

Question 34

What is accommodation?

Answer 34

Rounding of the lens for near vision

Question 35

How is myopia treated?

Answer 35

a concave lens is placed in front of the eye to help spread out light rays