COM 1 Physiology week 6

Question 1

Name the layers of the eye

Answer 1

1. Outer fibrous layer
2. Middle vascular layer
3. Inner Neural layer

Question 2

What does the outer fibrous layer contains

Answer 2

Cornea, corneal epithelium, conjunctiva, sclera

Question 3

What does the Middle Vascular layer contasij

Answer 3

Iris +choroid

Question 4

What does the inner neural layer contain

Answer 4

Retina

Question 5

What is the function of the lens

Answer 5

Focuses light onto the retina

Question 6

When does refraction occur

Answer 6

It occurs when a wave changes directions a it passses from one medium to another due to a change in speed or medium

Question 7

What does the refractive index of material determine

Answer 7

How much light is refracted

Question 8

Name the 4 refractive interfaces which the eye has

Answer 8

-Interference between air to the surface of the cornea
-Posterior surface of the cornea to aqueous humor.
Aqueous humor to the anterior surface of the lens.
Posterior surface of the lens to vitreous humor.

Question 9

What is the refractive indices of the materials :
-Air
-Cornea
-Aqueous humor
-Lens
-vitreous humor

Answer 9

Air: 1
Cornea: 1.38
Aqueous humor: 1.33
Lens: 1.40 (average)
Vitreous humor: 1.34

Question 10

How much of the eyes refractivee Power does the cornea provide

Answer 10

The cornea provide 2/3 of the eyes refractive power

Question 11

What is accommodation

Answer 11

When the interna lens of the eye can change its culture in response to nervous signals form the brain

Question 12

Explain the processin formation of an imagine on the retina
-Starting from the lens system
-How the brain precieves the image

Answer 12

The lens system of the eye focuses an image on the retina, which is inverted and reversed compared to the object.

The brain perceives the image upright because it is trained to interpret an inverted image as normal.

Question 13

Explain how/THE MECHANISM of how the lens can change shape in childre

Answer 13

-The lens increases in refractive power
-Then the lens change from moderately convex to very convex

Question 14

Explain how the ciliary muscle controls the shape of the lens

Answer 14

And the ciliary muscle controls the shape of the lens throgh its meridional and circular muscle fiibers

Question 15

Explain how the parasympathetic nerves control the cillary in accommodation
+ what happens when it is stimulated

Answer 15

Parasympathetic nerve signals from the third cranial nerve control the ciliary muscle.

When stimulated, these nerves contract the muscle, releasing the tension on the lens, allowing it to thicken and focus on nearby objects.

Question 16

What is presbyopia

Answer 16

Loss of accommodation

Question 17

Explain why presbyopia/ loss of accommodation occurs

Answer 17

As a person ages, the lens becomes thicker and less elastic, reducing its ability to change shape.

The power of accommodation decreases with age,

Question 18

What is the effect of people with presbyopia(loss of accommodation) + what do they require

Answer 18

• They can no longerfocus on both near and far objects, requiring bifocal glasses for clear vision at differnet distances

Question 19

Depth of focus increases with what? and why

Answer 19

A smaller pupil diameter, which keeps the images in sharp focus

Question 20

Name the 3 errors of refraction + their alternative names

Answer 20

• Emmetropia- Normal vison
  -Hyperopia-Farsightedness
  -Myopia-Nearsightedness

Question 21

Explain emmetropia(normal vision)- when is the eye normal

Answer 21

The eye is normal when parallel light rays focus sharply on the retin with the cilary muscle relaxed

Question 22

What is hyperopia (farsightedness) caused by

Answer 22

• Short eyeball or weak lens system, where the light rays do not focus on the retina without accommodation

Question 23

What is myopia(nearsightedness) caused by

Answer 23

• Caused by a long eyeball or too much refractive power, where the distant light rays focus in fornt of the retina

Question 24

Name the lens that corrects myopia

Answer 24

• Concave lens

Question 25

Name the lens that corrects hyperopia

Answer 25

- Convex lens

Question 26

How does concave lens correct myopia

Answer 26

- By diverging light rays before they enter the eye

Question 27

How does convex lens correct hyperopia

Answer 27

By converging light rays before they enter the eye

Question 28

What is Astigmatism

Answer 28

A refractive error where light focuses at different distances in differnt planes due to uneven curvature of the cornea

Question 29

How is Astigmatism corrected

Answer 29

- Using cyclindrical lens, which adjust the focus along the different axes

Question 30

What is the function of contact lens

Answer 30

They neutralize the refractive power of the cornea,

Question 31

What are the 2 advantages of contact lens

Answer 31

- Provide a wider field of clesr vison -No image size distortion

Question 32

What are Cataracts+ what is it formed by

Answer 32

They are opaque areas in the lens formed due to protein denaturation

Question 33

When cataracts impair vison, when it done to the lenes

Answer 33

Surigcal removal of the lens is reuired

Question 34

What is the diamater of the cones in the fovea

Answer 34

1.5 micrometers

Question 35

Where does the maximum visual acuity occur

Answer 35

Fovea

Question 36

Where does visual acuity decrease towards to

Answer 36

- The periphery of the retina

Question 37

How is visual acuity tested

Answer 37

- It is tested using leters on a chart at a distance of 20 feet

Question 38

What does 20/20 vision indicate

Answer 38

Normal vision

Question 39

What are the 3 ways to perceive distance

Answer 39

- Sizes of retinal images -Moving parallax -Stereopsis

Question 40

If someone can read letters meant for 200 feet what type of vision do they have

Answer 40

20/200 vision

Question 41

What does the eye contain

Answer 41

- Aqueosu humour and vitrous humor

Question 42

Explain the differnece between aqueous humor and vitreous humor

Answer 42

Aqueous humor flows freely, while vitreous humor is more gelatinous

Question 43

What does aqueous humor maintain

Answer 43

- Intraocular pressue

Question 44

What is the aqueous humor secreted by

Answer 44

- Ciliary processes

Question 45

How is aqueous humor formed

Answer 45

By the active transport of the sodium ions into the ciliary proceses , which draws chloride and bicarbonate ions with them , causing water to move through osmosis

Question 46

Name 3 nutrients that are transported across the ciliary process during aqueous humor formation

Answer 46

- Amino acids -Ascorbic acid -glucose

Question 47

What is the function of the canal of schlemm in relation to aqueous humor

Answer 47

- Allows the passage of aqueous humor

Question 48

Where does aqueous veins carry aqueous humor from and to

Answer 48

- The canal of schlemm to larger veins

Question 49

What is used to meaure intraocular pressure

Answer 49

Tonometry

Question 50

Explain how a tonometer works in measuring intraocular pressure

Answer 50

It applies a small force to the cornea and te displacemnt is recorded to determine pressure

Question 51

What is glaucoma caused by

Answer 51

High introcular pressure, due to debris accumulating in the trabecular spaces

Question 52

What can glaucoma cause

Answer 52

Blindness by compressing the optic nerve

Question 53

The photoreceptors in the retina are either what?

Answer 53

rods or cons

Question 54

What are rods and cones responsible for

Answer 54

- Recieving and transducing visual information

Question 55

What are rod cells rich in

Answer 55

rhodopsin

Question 56

Explain the sructure of photorecetopres-segmentd

Answer 56

-contain both rods and con cells -Outer segments : contain rod and cone cells -Inner segments contain mitochondria and organelles -Site of rhodopsin synthesis

Question 57

What is the function of the phototransudction process

Answer 57

converts light energy into eletrical signlas

Question 58

What is the photosensitive pigment+ what is it composed of

Answer 58

Rhodopsin, composed of opsin

Question 59

What does cutting the optic nerve rsult in

Answer 59

blindeness in the eye

Question 60

what does cutting the optic chiasm result in

Answer 60

loss of temporal fields

Question 61

What is the visual cortex divided into

Answer 61

-Primary visual cortex -Secondary cortex

Question 62

Where is the primary visual cortex+ where does it recieve input from

Answer 62

calcarine ifssure area -retina

Question 63

What number is the primary visual cortex

Answer 63

V1

Question 64

wHAT NUmbers is the secondary visual cortex

Answer 64

v2-V5