Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

control of human movement > vision > Flashcards

vision Flashcards

1
Q

what’s the role of the iris ?

A

changes size accommodate image in the pupil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

in what order does light travel through the eye ?

A

cornea

lens

vitreous humour

retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does it mean when we foveate ?

A

bring image to central part of the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why is there many blood vessels in the eye ?

A

high metabolic activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is special about the lens ?

A

gelatinous material

designed to change shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what moves the lens ?

A

cililary muscles which are attached through zonular fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the measure of lens focussing power ?

A

dioptere

average human eye 57-60 diopteres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what determines lens strength ?

A

curvature and refractive index

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

where does refraction usually occur ?

A

cornea
48 ou tof 57 D

further refraction caused by lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is meant by accommodation ?

A

focal length is changed by altering lens shape

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what happens when the ciliary muscle contracts ?

A

loosens zonular fibres

causes lens to squish spherically

relieves ligament tension on lens

increases lens power

shortens focal length for closer objects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what happens when ciliary muscles relax ?

A

tightens zonular fibres

make sense more flat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what happens when our lens is in focus ? - far away object (4)

A

relaxed ciliary muscles

tension on zonular fibres

flattened lens

light rays nearly parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what happens when the lens is out of focus ? (2)

A

relaxed ciliary muscles

light rays from near objects diverge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what happens when the lens is in focus? - close up object (4)

A

contraction on ciliary muscles

relaxed zonular fibres

rounded lens

accommodation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is myopia ? (4)

A

short sightedness

eye is too long

image focusses before hitting retina

concave lens helps reverse some refraction to bring focal point to retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is hypermetropia ? (4)

A

long sightedness

eye is to short

image focussed behind the eye

glasses lenses are thicker in middle , helps bring image forward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is presbyopia ? (3)

A

when lens siezes up with age

doesn’t bulge when ciliary muscles contract

near point moves away

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does the pupil do in relation to light ? (3)

A

diameter changes light levels 2-8mm

can alter amount of light captured by 16 times

only a small portion of how the eyes adapt to light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what are the pupil diameter muscles and what do they do ?

A

sphincter pupillae- contracts making pupil smaller

dilator - contracts making pupil bigger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

why do we see better with a smaller pupil ? (3)

A

higher quality image

greater depth of filed

compensates for myopia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

why is a larger pupil size less effective ?

A

more scattered light and glare

increased spherical aberration - blurry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what does reduced sensitivity to light do ?

A

reduced quality of image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is an ophthalmoscope ?

A

tool that shines light to back of retina

has an adjustable lens that can bring retina to focus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what does it mean if the fovea has a high density ofphot receptors

A

higher aquity - image quality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what re the 5 retinal cells ?

A

rods

cones

horizontals

bipolars

ganglion

27
Q

which retinal cells can carry an AP ?

A

ganglion

28
Q

what is special about the structure of the retina and how light travels through?

A

the photoreceptors are on the outside

light has to travel through the structures to reach them

its adjacent to the pigment epithelium which minimises reflectance

29
Q

what’s special about the foveal retina ?

A

structures int he foveal retina are pushed to one side which reduces light scattering

increases acuity

30
Q

what is the role of black pigment epithelium

A

minimises reflectance

31
Q

what’s is the structure of rods and cones ?

A

folds of membrane that create disks

the disks contain photopigment

32
Q

what is relevant in term son rods and cones density ?

A

acuity can be defined by the pointspread function

  • determines the minimum separation of 2 points before the are perceived as 2 separate entities
33
Q

what is photopigment ?

A

2 molecules ( retinal + opsin) combien to create photopigment

this is called rhodopsin in rod cells

34
Q

what is photopigment bleaching ?

A

rhodopsin interacts with a light photon causing configurational change

retinal and opsin then part - bleached

35
Q

how is the cell membrane hyperpolarised? (5)

A

opsin activates phosphodiesterase (PDE)

PDE converts cGMP to GMP

this opens Na channels

closure of the Na channels cause hyperpolariastion

due to K leaking out

36
Q

how does the firing rate of the ganglion cell change ?

A

rod/cone hyperpolariastion causes LESS neurotransmitter release
(glutamate)

this modulates the membrane potential of the bipolar cell

inhib/excite

37
Q

what is scotopic vision ? (4)

A

low light vision

rods only

high sensitivity

low acuity

38
Q

what is photopic vision ? (6)

A

high luminance

cones only

rod cells wont work - bleached

low sensitivity

high acuity

foveal + peripheral

39
Q

what are the 4 adaptations to luminance ?

A

pupil size

switch between rods and cones

dark adaptation

field adaptation

40
Q

what is dark adaptation?

A

bleaching/ regeneration of photopigment

less light is needed to bleach which aids regeneration to protects light

41
Q

what is field adaptation ?

A

quick light adaptation

automatic gain control within the photoreceptor

calcium release mechanism in the photoreceptor

42
Q

adaptation is a constant trade of between what ?

A

sensitivity vs acuity

43
Q

which is more sensitive: rods or cones ?

A

rods

by 1 order of magnitude

44
Q

where does more sensitivity come from in terms of cells ?

A

high convergence of rods onto ganglion cells via bipolar cells

degree of convergence depends on the light conditions

45
Q

if only cones are used for colour vision in mesonic and scotopic vision, does it get better or worse ?

A

colour vision gets worse if only cones are used

46
Q

explain the distribution of rods and cones in the retina (4)

A

foveal vision is dependent on cones

centre of the eye has high density of both rods and cones

cones in periphery are poor compared to rods

foveal acuity at night is poor

47
Q

what is meant by acuity ?

A

our ability to see sharp and defined shapes at certain distances

48
Q

explain the processing of info after the photoreceptor (4)

A

retinal processing reduces things of interest in our scenery

changes both spacial and temporal imagery/field

brain can recognise shapes through spatial awareness of edges

helps us identify what we look at

49
Q

what is the concept of the receptive field ? (4)

A

ganglion cell is final output of retina

each ganglion responds to many photoreceptors

some photoreceptors excite/inhibit ganglion cell

forms centre surround shape - causes lateral inhibition

50
Q

what is lateral inhibition ?

A

mediated by horizontal cells

retinal ganglion cells are set up to detect edges

respond better to both light and dark (shadows) rather than pure light and pure darkness

51
Q

what is a contrast illusion ?

A

an illusion where the perceived brightness or identical visual targets seems to differ depending on its background and ratio of brightness

looks diff but is the same lol

52
Q

what is the theoretical 1 channel receptor system in terms of colour ?? (4)

A

responds to stimulus intensity

one degree of freedom

no discrimination except brightness

monochrome system- limits ability to judge light

53
Q

what is the theoretical 2 channel receptor system in terms of colour ?? (5)

A

responds to 2 aspects of stimulus intensity

2 degrees of freedom

can discriminate colours

outputs are described by 2 numbers

can be ambiguous

54
Q

what’s the colour triangle ?

A

assumes constant luminance of all colour wavelengths

any colour can be dialled by combo of red, green and blue

55
Q

what are the 2 factors that colour can be defined by ?

A

saturation - strength of colour

hue - defines colour itself

56
Q

what does no wavelength stimulate in terms of colour ?

A

green cones

no need to activate red+blue

57
Q

where does colour processing mainly take place ?

A

retina

58
Q

how do ganglion cells respond to colour?

A

responds to combination of red, green or blue

doesn’t respond indiv

59
Q

to activate the blue photoreceptor what happens ?

A

yellow inhibits blue

60
Q

to activate the green photoreceptor what happens ?

A

red inhibits green

61
Q

what are the types of colour disorders ?

A

pronatopes - no red

dichromats - no green

tritanopes - no blue

62
Q

what is meant by the brain is contralateral in terms of visual info ?

A

optic nerve splits at the optic chiasm

left eye - right hemisphere of brain and vice versa

63
Q

how is info related to the visual cortex of the brain ?

A

via the lateral geniculate nucleus - in thalamus

64
Q

how is location of blindness useful ?

A

can help localise the anatomical lesion

blindness in one eye- optic chiasm defecit

part blind in both eyes - visual cortex / optic chiasm

control of human movement (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions