Lecture 1- Eyes

Question 1

What are the special senses?

Answer 1

Vision, smell, taste, hearing and equilibrium

Question 2

Special sensory receptors

Answer 2

Distinct receptor cells located in the head region

Question 3

Which sense is most dominat?

Answer 3

Vision

70% of sensory receptors are found in the eye

Question 4

Accessory structures of eye

Answer 4

eyebrows
eyelids
conjunctiva
lacrimal apparatus
extrinsic eye muscles

Question 5

What does the eye consist of?

Answer 5

Accessory structures and the eyeball

Question 6

Palpebrae (eyelids) and eyelashes

Answer 6

protect eye from physical danger as well as drying out

Question 7

Conjunctiva

Answer 7

Transparent membrane that produces lubricating mucus to prevent eye from drying out

Question 8

What does Lacrimal apparatus consist of?

Answer 8

lacrimal gland, that secretes a dilute saline solution (tears) and small ducts that drain excess fluid into the nasolacrimal duct.

Question 9

What does lacrimal fluid contain?

Answer 9

mucus, antibodies, and lysozyme to cleanse, moisten, and protect the eyes.

Question 10

What is the movement of each eyeball controlled by?

Answer 10

six extrinsic eye muscles that are innervated by the abducens and trochlear nerves.

Question 11

What are the Three layers the wall of the eye is composed of?

Answer 11

Fibrous
Vascular
Inner layers (retina,neural)

Question 12

Fibrous layer

Answer 12

Two regions

Sclera (white part of eye) and cornea (clear, allows light in)

Question 13

Sclera

Answer 13

White part of eye

Question 14

Cornea

Answer 14

Clear and allows light to enter the eye

Question 15

Anterior cavity

Answer 15

Before lens

filled with aqueous humour, that supplies nutrients and oxygen to lens and cornea while carrying away wastes.

This fluid is continuously produced and drains away.

Question 16

Posterior cavity

Answer 16

After lens

filled with clear gel called vitreous humour that transmits light, supports posterior surface of lens, holds retina firmly against pigmented layer, and helps maintain intraocular pressure.

Question 17

Choroid

Answer 17

vascular middle layer of tissue that nourishes eye layers.

Question 18

Ciliary body

Answer 18

consists of smooth muscle that encircles the lens, determining its shape and controlling the amount of light that enters the eye.

Question 19

Iris

Answer 19

surrounds the pupil, controls pupil size and the amount of light that enters the eye.

Has only one colour - brown

Question 20

What does the Inner layer of eye contain?

Answer 20

the photoreceptors, rods and cones, as well as bipolar cells, ganglion cells, and glia.

Question 21

What does Neural layer of retina include?

Answer 21

an optic disc (blind spot), where the optic nerve exits the eye; there is no room for photoreceptors here.

Question 22

Macula lutea

Answer 22

has a pit in its centre called the fovea centralis.

Question 23

Fovea centralis

Answer 23

has the highest density of cones, producing the most detailed colour vision.

only contains cones, so that is the region with the best visual acuity. We move our
eyes to focus the image of an object on the fovea.

Question 24

Rods

Answer 24

highly sensitive to light

best suited to night vision but cannot resolve colour or sharp images.

found in your peripheral vision and are more numerous than cones.

Question 25

Cones

Answer 25

less sensitive to light

best adapted to bright light and provide high-resolution colour vision.

Humans have three kinds of cones.

Question 26

Glaucoma

Answer 26

condition in which drainage of aqueous humor is blocked, causing fluid to back up and increase pressure within the eye.

Pressures may increase to dangerous levels and compress the retina and optic nerve, leading to blindness.

Question 27

Cataracts

Answer 27

clouding of the lens that can cause dim vision, blurry vision, faded colours, trouble with bright lights and trouble seeing at night.

Question 28

Lens

Answer 28

avascular, biconvex, transparent, flexible structure that can change shape to allow precise focusing of light on the retina.

Question 29

Distant vision

Answer 29

ciliary muscles are completely relaxed causing maximum flattening of the lens.

Question 30

Far point of vision

Answer 30

The distance beyond which no change in lens shape is required.

In a normal eye, this is a distance of about 6 meters, or 20 feet.

Question 31

Close vision

Answer 31

Lens thickens to increase light refraction

Pupils constrict to better direct light into lens

Convergence of eyeball to allow object to remain focused on foveae

Question 32

Near point of vision

Answer 32

occurs at the point of maximal thickening of the lens, and is 10 cm, or 4 inches, from the eye.

Question 33

Myopia (nearsightedness)

Answer 33

Occurs when objects focus in front of retina

Can see close objects without a problem but distant objects are blurred

Question 34

Hyperopia (farsightedness)

Answer 34

Occurs when objects focus behind retina

Can see distant objects clearly but close objects are blurred

Question 35

Astigmatism

Answer 35

results from an uneven curvature of the cornea or lens, which produces blurred images.

Question 36

What must light pass through in order to be detected?

Answer 36

cornea, aqueous humour, lens, vitreous humour, the entire neural layer of retina, and finally arrive at the photoreceptors.

Most refraction occurs at cornea but it cannot change focus