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PSL300 > week 8 > Flashcards

week 8 Flashcards

1
Q

4 somatic senses

A

touch, temperature, proprioception, nociception

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2
Q

5 special senses

A

vision, hearing, equilibrium, taste and smell

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3
Q

receptor potential

A

a receptor cell converts stimulus energy into a graded change in membrane potential. – receptor may then release neurotransmitter to affect a neuron, if the receptor is itself a neuron, it may fire action potentials.

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3
Q

transductions

A

receptors convert stimuli into electrical signals

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4
Q

receptor cells

A

in some sensory systems (vision), receptor cells are neurons; in others (hearing) they are non neuronal epithelial cells

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5
Q

adeuqate stimulus

A

form of energy to which a receptor cell is most responsive, but many receptors also respond to other forms of energy

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6
Q

perceptual threshold

A

weakest stimulus that will cause a conscious perception in an organism

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7
Q

receptor threshold

A

weakest stimulus that will cause a response in the receptor

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8
Q

what allows secondary and higher neurons to combine data from many receptors

A

convergence

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9
Q

stimulus modality

A

what stimulus is it? light sound, etc

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10
Q

population coding of intensity

A

Stronger stimuli may activate more neurons.

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10
Q

frequency coding

A

Stronger stimuli may make individual neurons fire at a faster rate

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11
Q

what sensory systems indicate modality by

A

labeled lines

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12
Q

labeled lines

A

modality is revealed by which axons carry a signal

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13
Q

phasic cells

A

respond briefly to any cells and then cease firing

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14
Q

phasic-tonic cells

A

react to change but dont return all th way to sero firing when the stimulus is constant, so they also carry information about its steady level

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14
Q

tonic cells

A

maintain their activity when the stimulus is not changing, signalling its present level

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15
Q

temporal changes

A

changes through time

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16
Q

what cells are phasic

A

many retinal cells are phasic

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17
Q

contrast

A

location where there is strong contrast are called edges

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17
Q

where do most sensory pathways run

A

via thalamus to cortex
exception: olfactory pathways don’t project via the thalamus
equilibrium pathways project mainly to cerebellum

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18
Q

spatial changes

A

differences between neighbouring regions in space; also called contrast

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19
Q

why is sensory processing inference?

A

sense data are incomplete and ambiguous so the brain has to infer

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19
Q

lateral inhibition

A

cells inhibit their neighbours or they inhibit the cells their neighbours excite

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20
Q

how do sensory system accentuate edges

A

lateral inhibition

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21
Q

what suspends the lens

A

ligaments called zonules

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22
Q

lens

A

trasnparent disc that focuses light

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23
Q

2 chambers in eye

A

anterior chamber (front of lens) and vitreous chamber (behind lens)

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24
Q

vitreous chamber

A

filled with vitreous body (clear jelly) that helps maintain the eyeballs shape

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25
Q

anterior chamber

A

filled with aqueous humour (plasma like fluid)

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26
Q

what does light enter the eye through

A

cornea

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27
Q

cornea

A

transparent bulge at the front of the eye, continuous with the white of the eye (sclera)

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28
Q

where do cornea and lens focus light

A

retina

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29
Q

retina

A

inner lining of the eye that contains photoreceptors

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30
Q

when and how does the pupil constrict

A

in bright light, parasympathetic signals from the brain contract the ring-shaped pupillary constrictor muscles, shrinking the pupils

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30
Q

how does light pass from cornea to lens

A

through a hole in the iris called a pupil

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31
Q

when and how does the pupil dilate

A

In the dark, sympathetic signals contract the radial pupillary dilator muscle of the iris, dilating the pupil

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32
Q

how does the pupil control the depth of field

A

when the pupil is tightly constricted we have full depth of field, when pupil is dilated, we have a shallow depth of field

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33
Q

what is light refracted by

A

cornea (2/3rd) and lens (1/3rd)

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34
Q

what is lens made of

A

it is a mesh of long cell without nuclei, packed with clear proteins called ccrystallins and ‘zippered’ together in concentric layers for flexibility. it has no blood supply but abrsorbs nutrients from aqueous humor.

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35
Q

shape of lens

A

convex - thick in the middle and thinner at edges

35
Q

what does the convex shape of lens do

A

makes light rays converge to a focal point

36
Q

concave lenses

A

thinner in the middle and fatter at the edges

36
Q

what does refraction depend on

A

angle of incidence

37
Q

when does a light ray not bend at all

A

when it strikes the lens at right angles

38
Q

what does a rounder lens do

A

bends light more, so has a closer focal point

38
Q

for clear vision where must the focal point fall

A

retina

39
Q

what happens if an object draws closer but lens stays flat

A

focus falls behind the retina

40
Q

how do we make a lens rounder

A

parasympathetic nerve signals contract the ring-shapes, smoothe ciliary muscle, reducing tension in the zonules, making the lens rounder, so light rays bend more and the focal point moves forward.

41
Q

how do we make a lens flatter

A

sympathetic signals relac the ciliary muscle, making the lens flatter for far vision

42
Q

accomodation

A

rounding the lens for near vision

43
Q

near point of accomodation

A

closest point a person can focus

44
Q

myopia; how is it solved?

A

(near-sightedness) the focal point falls in front of the retina; solved by concave lens in front of the eye

44
Q

hyperopia; how it solved?

A

(far-sightedness) the focal point falls behing the retina ; solved by convex lens in front of eye

45
Q

presbyopia

A

with advancing age the lens stiffens, hindering accommodation

46
Q

where are photoreceptors?

A

retina

47
Q

phototransduction

A

conversion of light energy into electrical energy

48
Q

2 main types of photoreceptors

A

cones (6 mil) rods (120 mil)

49
Q

how do rods and cones respond to stimuli?

A

they are neurons, though they do not fire action potentials, but instead respond to stimuli with graded membrane potentials

50
Q

basic structure of rods and cones (outer segment)

A

membrane folds into disc-like layers which contain visual pigments that respond to light

51
Q

basic structure of rods and cones (inner segment)

A

there are nucleus and organelles for protein synthesis; and in a basal layer, a synapse that releases glutamate

52
Q

where do both types of receptors point towards

A

back of the eye

53
Q

what happens to photoreceptors in light

A

when light hits them, pigment molecules change shape, starting a chemical cascade that hyperpolarizes the cell, reducing its release of glutamate

54
Q

what happens to photoreceptors in dark

A

get depolarizedd and release more glutamate

55
Q

type of pigment in rods

A

rhodopsin

56
Q

types of pigments in cones

A

3 types of pigments in 3 types of cones

57
Q

where are photoreceptors most densely packed

A

macula, a central disk and especially in its central pit called the fovea

58
Q

what do we use the fovea for

A

detailed vision - 5 degreed away from its center acuity is quartered, at 20 degrees it falls below thee standard for legal blindness

59
Q

where are there no receptors

A

blind spot, it is the hole where axons carrying visual information exit the eyeball to form the optic nerve

60
Q

what happens when lights go dim

A

rods dark adapt

60
Q

What are rods responsible for

A

they can detect single photons. but the operate only in low light: in daylight the are bleached out, their rhodopsin is broken down so they cant sense light

61
Q

what are cones reponsible for

A

right light
they are less sensitive than rods; responsible for vision in bright light and for distinguishing colours, but they don’t operate in dim conditions

62
Q

distribution of rods and cones

A

fovea contains most exclusively cones. more peripheral retina contains mainly rods

63
Q

where is convergence the greatest

A

peripheral retina

63
Q

layers of neurons in retine

A

photoreceptors synapse onto bipolar cells which synapse onto ganglion cells

64
Q

where is convergence the least

A

fovea

65
Q

receptive field

A

also called visual field, region of the retina where light affects the cell’s activity

66
Q

what type of receptive fields do bipolar cells have

A

center-surround fields

67
Q

types of center surround receptive field in bipolar cells

A

on center or off center

68
Q

on center cells

A

excited by light in the center of their field and inhibited by light in the surround. so these cells respond most when a light spot fills their center and the surround is dark.

69
Q

off centre cells

A

inhibited by light in the centre, and excited by light in the surround. they respond best when a dark spot fills their center and the surround is light.

70
Q

when do bipolar cells react

A

contrast
they respond with graded potentials and do not fire action potentials

71
Q

how do ganglion cells react

A

they fire action potentials

72
Q

similarity between ganglion cells and bipolar cells

A

they have on-center and off-center surround receptive field and detect contrast

73
Q

where does a ganglion cell farther out get input from

A

many receptors, mostly rods
very sensitive to light but poor at reporting spatial detail as it blends information from a wide swathe of receptors

73
Q

where does a ganglion cell near the fovea get iinput from?

A

few photoreceptrs and mostly cones
less sensitive to light but have =e better spatial resolution

74
Q

types of ganglion cells

A

M cells, P cells, melanopsin ganglion cells

75
Q

M cells

A

Large, magnocellular ganglion cells; provide inforamtion that is used by the brain to infer the movement of objects
10%

76
Q

P cells

A

small, parvocellular gaanglion cells
provide infoamrtion that is used to infer form and fine detail
70%

77
Q

melanopsin ganglion cells

A

photoreceptors with own visual pigment (melanopsin)
they project to the suprachiasmatic nucleus, a center for circadian rhythms

78
Q

how does visual information leave retinas

A

in optic nerves/cranial nerve II

79
Q

where do half the optic nerve fibers cross

A

optic chiasm

80
Q

which fibers optic nerve cross

A

fibers from the nasal half of each retina cross; those from the temporal retinas do not

80
Q

why do optic fibers cross

A

in the eye, the right side of the scene projects on the left side of the retina; i.e. on the nasal side of the right retina and temporal side of the left retina

81
Q

how does visual info move

A

information moved from the chiasm to thalamus and then to cortex

82
Q

what are nerve bundles emerging from the chiasm called

A

optic tracts

83
Q

what do optic tracts end in

A

2 lateral geniculate nuclei in the thalamus, which project via the optic radiation to primary visual cortex, V1

84
Q

where is V1 located

A

occipital lobe

85
Q

how are many visual area in brain organized

A

retinotopicallu; neurons close to each other in brain get information from close together parts of the retina
this arrangement is found in lateral geniculate nuclei, V1 and others higher visual processing areas

86
Q

explain how the retinotopic map does not preserve areas

A

the fovea, which cover only a small part of the retina projects to large areas in the V1

PSL300 (19 decks)

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