NS: Eye

Question 1

Parts of the outer eye and function

Answer 1

• Eyelid (protection)
• Orbital Cavity (support,
  protection)
• Eyelashes (dust)
• Lacrimal Ducts (tears, antibacterial)
• Extrinsic Muscles (voluntary eye movement
• Conjunctivia (transparent mucous membrane lining inner surface of eyelids, and fold back to cover front surface of eyeball)

Question 2

Conjunctivitis

Answer 2

• aka pink eye

- inflammation of conjunctivia caused by bacteria or allergies

Question 3

Sclera

Answer 3

• Dense white connective tissue
• Outermost layer
• Avascular (not a lot of blood)
• Maintains shape
• Cornea is a portion of sclera

Question 4

Cornea

Answer 4

• Clear portion of sclera
• Covers front of eye
• Focus and protect eye
• aqueous humor (fluid behind cornea) supplies nourishment

Question 5

Choroid Layer

Answer 5

• Middle layer btwn sclera and retina
• Vascular (nourishes retina)
• Contains melanin to prevent light from scattering

Question 6

Iris

Answer 6

• Circular muscle (involuntary)
• Controls amount of light entering eye (controls pupils, contracts and dilating)
• Coloured

Question 7

Pupil

Answer 7

• Opening inside iris
• Size depends on light intensity
• Melanin: black pigment that makes pupil look black (from choroid layer, btwn sclera n retina)

Question 8

Lens

Answer 8

• Behind Iris
• Transparent, biconcave, elastic, soft, avascular disc
• Held in place by ciliary muscles
• Changes shape to focus image onto back of retina

Question 9

Retina

Answer 9

• Innermost thin layer on back of eye cavity
• Contains photoreceptors which converts light to nerve impulses
• Lens focuses images on retina
• has 4 layers: pigmented epithelium (prevents light from scattering), light sensitive cells, bipolar cells, cells of optic nerve

Question 10

Eye cavities and functions

Answer 10

1. Anterior eye cavity: “aqueous humor”, maintenance of shape, nourishment and focus
2. Posterior eye cavity: “Virtreous humor”, Maintains shape of eyeball and permits light transmission to retina

Question 11

Photoreceptors

Answer 11

-Two types of photoreceptors

1. Rod: for light
2. Cones:for colour

Question 12

Rods

Answer 12

-Light sensitive cells on the periphery of the retina
-many rods per neuron
-18 million times as many rods as cones in the retina
-Detect low intensity light ( black and white and shades if grey) -> most effective at dusk and dawn (limited light)
contains a light sensitive pigment called rhodopsin
-For the rods to continue to work,rhodopsin levels must be maintained.
-vitamin A deficiency can permanently damage the rods

Question 13

Rhodopsin

Answer 13

1. Retinal (derivative of vitamin A)

2. Opsin protein

Question 14

Cones

Answer 14

Cones are responsible for seeing colour
3 types of opsin proteins: sensitive to blue/green/red wavelengths of light (low light)
each type determines frequency of light able to be absorbed
high concentration of cones in the fovea centralis
fewer # than rods
1:1 ratio with neurons
100 cones : 1 ganglion

Question 15

Fovea Centralis

Answer 15

Region with highest concentration of cones (detailed colour vision)
rods are around the fovea
depression in middle of retina

Question 16

Order of Light Transmission

Answer 16

1. light enter
2. strikes retina (pigmented epithelium)
3. rods, cones (sensory receptors on retina) > release neurotransmitters
4. Bipolar cells
5. Ganglion Cells > form optic nerve
6. optic nerve > thalamus
7. Occipital Lobe

Question 17

Ganglion cells

Answer 17

emphasize differences btwn images

Question 18

Horizontal cell

Answer 18

connect photoreceptors to bipolar cells

Question 19

Amacrine cells

Answer 19

Light adaptation and moving objects

Question 20

Pathway of focusing an image

Answer 20

• when light enters the eye
• light bent into pupil by cornea (light slows down when it enters the more dense media like cornea)
• Cornea directs light inward towards the lens (further bending), ciliary muscles control the shape of the lens, suspensory ligaments (on lens) maintain tension
• Inverted image is projected onto retina (light is directed at a focal point)

Question 21

Neural Pathway of light

Answer 21

1. Optic Nerve
2. Optic Chiasm
3. Primary visual cortex: Occipital lobe of cerebrum
   l
4. Visual association area

Question 22

What happens at Optic Nerve (Neural Pathway of Light)

Answer 22

• All ganglion cells come together to form one optic nerve
• Carries impulses to brain
• Is the blind spot on retina (where optic nerves and vessels exist, there r no photoreceptors)

Question 23

Role of Optic Chiasm (neural pathway of light)

Answer 23

• Nerves from both eyes come together and some cross to opposite sides of brain
• Outside stays but inside crosses
• Allows eyes to work as pair

Question 24

Primary visua cortex: Occipital lobe (neural pathway of light)

Answer 24

• Receive info from optic nerves

- Does not interpret info

Question 25

Visual association area (neural pathway of light)

Answer 25

- Interpretation of visual info | - turns image right side up n gives it meaning

Question 26

Accommodations for eyes

Answer 26

- Adjustment made by lens and pupil for near and distant things - Increased age= decreased accommodation - Tendency of ppl needing glasses when older - Protein covering lens increase throughout whole life, make lens harder and less flexible

Question 27

Accommodation (for clarity of vision)

Answer 27

- ciliary muscle and suspensory ligaments accommodate lens to focus light on retina - Near objects: ciliary muscles contract, lens thick and round, bends light for more clearer vision - Far objects: ciliary muscles relax, lens thinner and flatter

Question 28

Accommodations (light intensity)

Answer 28

- changes diameter of pupil - near objects: pupil constricts to bring image into shape focus - far objets: pupils dilates to capture as much light possible into sharp focus

Question 29

Myopia

Answer 29

- Nearsightedness - can see close but not far - eye too long, lens cannot flatten enough - image focused in front of retina - treatment: concave lens

Question 30

Hyperopia

Answer 30

- Farsightedness - see far, not close - eye too short - lens too weak - image focused behind retina - treatment: convex lens

Question 31

Astigmatism

Answer 31

- abnormal curvature of cornea/lens | - treatment: glasses

Question 32

Cataracts

Answer 32

- cloudiness of cornea/lens due to lots of protein in lens | - treatment: corneal/lens transplant or strong contacts

Question 33

Glaucoma

Answer 33

- high pressure in anterior cavity (aqueous humour) due to inability to drain regularly - damages cells in retina - leads to blindness - treatment: eyedrops or laser eye surgery

Question 34

Color blind

Answer 34

- 1 or more cones defective - most common is red/green blindness - genetic and most common in males