Eye, visual pathway to brain LO5, LO6

Question 1

Lens

Answer 1

transparent and flexible
changes shape to focus light on retina

Question 2

Cornea

Answer 2

transparent layer that covers the anterior structures of the eye

Question 3

Iris

Answer 3

Coloured part of eye
muscles can constrict and dialate the diameter of pupil

Question 4

Pupil

Answer 4

Round central opening that allows light to enter

Question 5

Distant vision

Answer 5

• controlled by sympathetic NS
• clary muscles relax
• Suspensory ligament tighten, pull at circumference of lens which flatterns
• refraction of light decreases

Question 6

Close vision

Answer 6

• controlled by parasympathetic NS
• clary muscles contract
• Suspensory ligament loosen, lens becomes round and thick
• refraction of light increases

Question 7

Internal chambers

Answer 7

Anterior chamber: between cornea and lens
Posterior chamber: posterior to the lens

Question 8

Anterior chamber

Answer 8

contains aqueous humour: supplies nutrients and oxygen to the lens and cornea, removes waste

Question 9

Posterior chamber

Answer 9

contains vitreous humour: gelatinous substance that supports posterior surface of eye and holds retina in place

Question 10

3 layers fo the eye

Answer 10

fibrous layer (outer layer)
sclera – white, tough, opaque connective tissue, covers most of eye
cornea - transparent region at front of eye
Sclera, Choroid, Retina, Fovea centralis, Optic nerve, Optic disc (blind spot)

vascular layer (middle layer has 3 regions)
choroid – highly vascularised area
ciliary body – forms ciliary muscle rings around lens
iris– adjustable muscular layer that controls diameter of pupil

retina (inner layer): nervous layer
photoreceptors (cones and rods)
fovea centralis (visual acuity)
optic disc (blind spot)

Question 11

Fovea centralis

Answer 11

Region next to blindspot where all retina structures other than cones are displayed
allows light to pass directly to photoreceptors

Question 12

Rods

Answer 12

receptors for dim light and peripheral vision

Question 13

Cones

Answer 13

Receptors for bright lights, colour and visual activity

Question 14

Refraction

Answer 14

bending of light rays as it passes through different mediums

Question 15

Accommodation

Answer 15

changing the shape of the lens/increasing or decreasing the refractory power of the lens
results in light rays hitting retina

Question 16

Visual path to brain

Answer 16

Cornea - aqueous humor - pupil - lens vitreous - humor - retina - optic nerve - optic charisma - thalamus - optic radiations - PVC

Question 17

converting light rays into AP

Answer 17

Rods contain rhodopsin, which is very sensitive to light
light promotes the breakdown of rhodopsin causing the rod’s cell membrane to depolarise, which produces an action potential of the optic nerve.
cones function in a similar way using a different type of rhodop

Question 18

Optic disc

Answer 18

Lacks photoreceptors there light focused there cannot be seen

Question 19

Binocular vision and depth perception

Answer 19

human eyes are located anteriorly so the
field of vision from both eyes overlap
* two optic nerves meet at the optic chiasma and medial
fibers cross to the other side. Lateral fibre stay on same
side
* both hemispheres of brain
receive visual images from
both eyes
* each eye has a slightly different
image
* visual cortex fuses the 2 images
to provide depth perception:
ability to determine distance of
an object from the eye.