BMS11004 WEEK 8 - TUESDAY

Question 1

what is importance of vision

Answer 1

detect prey, predator, mates
communication

Question 2

name 3 words which describe light

Answer 2

visible electromagnetic radiation

Question 3

what is wavelength

Answer 3

distance between peaks/troughs

Question 4

what is frequency

Answer 4

number of waves per second

Question 5

what is amplitude

Answer 5

difference between wave peak and trough

Question 6

how does electromagnetic light travel

Answer 6

straight lines/rays until interact with atoms/molecules

Question 7

what 3 ways can light rays interact

Answer 7

reflection, absorption, refraction

Question 8

describe reflection

Answer 8

hits wall, and bounces off

Question 9

describe absorption of light ray

Answer 9

hits wall, it is absorbed by wall
photoreceptors and pigmented epithelium of retina

Question 10

describe refraction of light ray

Answer 10

hit wall, is bend and leaves at diff angles
bends due to difference in speed of light through different media

Question 11

explain monocular vision

Answer 11

one eye either side of head, large visual field = prey

Question 12

explain binocular vision

Answer 12

eyes facing out front of head, allow measurements of depth perception = predator

Question 13

what does the pupil do

Answer 13

let light inside eyes

Question 14

what does iris do

Answer 14

contain muscles that controls amount of light entering eye

Question 15

what does cornea do

Answer 15

glassy, transparent covering of pupil and iris that refracts light

Question 16

what does sclera do

Answer 16

continuous with cornea, forms tough protective wall of eyeball to give it its shape

Question 17

what does extraocular muscles do

Answer 17

move eyeball, controlled by oculomotor nerve (cranial nerve III)

Question 18

what does optic nerve do

Answer 18

carries axon from retina to brain (cranial nerve II)

Question 19

what does retina do

Answer 19

contain sensory receptor cells and afferent neurons

Question 20

what does lens do

Answer 20

suspended by zonal fibres (suspensory ligaments) which are attached to ciliary muscle, enabling lens stretch

Question 21

what is opthalmoscopes

Answer 21

shine light into eye and look at back of eye

Question 22

what is optic disk/blind spot

Answer 22

origin of blood vessels and optic nerve, cannot sense light

Question 23

what is macula

Answer 23

close to midline of nasal retina and temporal retina, for central vision
devoid of large blood vessels to improve vision quality

Question 24

what is fovea

Answer 24

retina is thinnest here, area of highest visual acuity
when not using fovea, side area of visual field = peripheral vision

Question 25

where should light rays be focused

Answer 25

onto retina, ideally onto fovea

Question 26

where do refraction occur

Answer 26

at cornea = 80% lens 20%

Question 27

what determines degree of refraction

Answer 27

difference in refractive indice between 2 media, and angle at whicb light hits interface between 2 medias

Question 28

outline refractive index

Answer 28

measure of speed of light within it light moves quicker through air than cornea due to increased density of cornea

Question 29

what cause refraction by cornea

Answer 29

light arrive at cornea via air, but cornea is mainly water and light travel slower water>air due to higher density, so cause refraction

Question 30

outline focal distance

Answer 30

distance from refractive surface to convergence of parallel light rays

Question 31

if light hits cornea directly perpendicular, what happens

Answer 31

move straight through onto retina

Question 32

explain refraction of light of images for distant/close objects through the cornea

Answer 32

distant = almost parallel light ray so cornea provides sufficient refraction to focus them onto retina closer = light ray not parallel, require additional refraction to focus them onto retina, provided by fattening of lens

Question 33

what does rounding of lens allow for focusing objects

Answer 33

increases refractive power to focus closer objects onto fovea

Question 34

explain when eye is emmetropic

Answer 34

when lens is flat and focusing on distant objects

Question 35

what is farsightedness (hyperopia)

Answer 35

eye too short and near objects focused behind retina, not enough refraction

Question 36

how can we fix farsighedness/hyperopia

Answer 36

convex glasses, make light coming from near object parallel

Question 37

explain shortsightedness/myopia

Answer 37

eye too long so distant objects focused before retina, too much refraction sees close up but not far away

Question 38

how is myopia fixed

Answer 38

concave lense

Question 39

what muscles contract to allow lens changing

Answer 39

contraction/relaxing ciliary muscles

Question 40

how is light focused onto retina converted into neural or electrical activity

Answer 40

photons pass through ganglion or bipolar cells before reaching photoreceptors, absorbed by pigmented epithelium

Question 41

name main retinal cell

Answer 41

ganglion cells bipolar cells photoreceptors

Question 42

name other retinal cells

Answer 42

amacrine cells (modulate info transfer between ganglion cells, bipolar horizontal cells (modulate info transfer between photoreceptors, bipolar)

Question 43

describe what ganglion cell do

Answer 43

output from retina

Question 44

explain what bipolar cells do

Answer 44

connect photoreceptors to ganglion cells

Question 45

explain what photoreceptors do

Answer 45

sensory transducers (rods and cones)

Question 46

outline the duplicity theory of photoreceptors

Answer 46

can't have high sensitivity and resolution in single receptor so needs separate system for monochrome and colour = rod, cone

Question 47

outline structure of rod photoreceptors

Answer 47

greater number of disk higher photopigment conc 1000x more sensitive to light than cones

Question 48

what type of vision does rod enable

Answer 48

enable scotopic (low light) vision = night time low visual acuity/resolution

Question 49

explain structure of cone photoreceptors, what type of vision they allow

Answer 49

fewer disks, used during daylight (photopic), enabling colour vision high visual acuity/res, low sensitivity

Question 50

when are rods and cones used together

Answer 50

in intermediate (mesopic) light

Question 51

does fovea contain more cones/rods, and what does this allow?

Answer 51

most of cones, no rods, allow low convergence on retinal ganglion cells so better for higher res vision

Question 52

what is convergence, sensitivity and resolution like on central retina

Answer 52

low convergence low sensitivity high resolution

Question 53

what is convergence, sensitivity, resolution like on peripheral retina

Answer 53

high convergence high sensitivity low resolution