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PSC1002- Physiology > nervous system L21-26 > Flashcards

nervous system L21-26 Flashcards

1
Q

3 sub-divisions of the somatosensory system

A

cutaneous
visceral
proprioception

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2
Q

function of touch sense

A

recognition and properties of things
control of movement
communication

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3
Q

steps in converting stimulus energy into action potentials

A
  1. sensory transduction
  2. action potential generation
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4
Q

sensory transduction

A

stimulus converted into a graded electrical potential/ receptor potential
depends on stimulus strength

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5
Q

action potential initiation

A

receptor potential exceeding threshold> action potential of nerve fibres
stimulus strength coded by firing rate

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6
Q

cutaneous receptors

A

superficial (merkel’s disc/ epidermal-dermal border/ free nerve ending/ meissner’s corpuscle)
deep (pacinian corpuscle/ ruffini’s corpuscle)

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7
Q

skin receptors defined by

A

location
size and structure
rapid/slow adaptation
size of receptive field

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8
Q

types of nerve fibres connecting to skin receptors

A

A-beta large diameter myelinated fibres
A-delta small diameter myelinated
C fibres small diamter unmyelinated

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9
Q

receptive field

A

area over which stimulus activates receptor associated w single neurone/ nerve fibre

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10
Q

rapidly adapting receptors

A

firing at stimulus onset
highlights appearance of new stimuli/ stimulus change

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11
Q

slowly adapting receptors

A

nerve continues firing action potentials throughout stimulus

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12
Q

pacinian corpuscle mechanical property changes

A

capsule present> rapid adaptation of receptor potential
capsule not present> less adaptation of receptor potential

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13
Q

pacinian corpuscle capsule

A

onion-like layers w fluid in between
rapid adaptation
allows for v rapid vibration

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14
Q

temp receptors

A

warm > C fibres
cold > A-delta fibres

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15
Q

nociceptors

A

noxious/ painful stimuli
mechanical/ thermal
sharp pain A delta followed by C fibre burn following

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16
Q

somatosensory system in rodents

A

modifiable (one-to-one anatomical relationship)
accessible (easy to perform targeted functional measurement)

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17
Q

2 pathways transmit cutaneous signals to the brain

A

dorsal column pathway
spinothalamic tract pathway

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18
Q

dorsal root ganglion

A

cell bodies of primary sensory nerve fibres
fibres enter spinal chord at root

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19
Q

nucleus

A

cluster of neurones in CNS w shared properties

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20
Q

dorsal column pathway

A

first synapse in dorsal column nuclei in medulla
decussation at medulla level L to R cortex / R to L cortex

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21
Q

dorsal column info carried

A

fine-discrimination touch
stimuli moving over skin surface
recognition of objects by touch

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22
Q

lateral inhibition in dorsal column

A

^stimulus contrast and therefore edges and form of tactile objects
fibres from neighbouring receptive fields inhibit one another

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23
Q

spinothalamic tract functions

A

coarse touch
temp
nociception

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24
Q

flexion/ extension

A

flexion> contract flexors and relax extensors
extension> relax flexors and contract extensors

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25
Q

synergists / antagonists

A

synergists> muscles pulling in same direction
antagonists> muscles pulling in opposite directions

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26
Q

neurones innervating muscle

A

large neurones
alpha motoneurones
in ventral horn of spinal chord

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27
Q

motor unit

A

motoneurone and muscle fibres it innervates

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28
Q

large motor unit

A

innervates many muscle fibres
strong force and little precision
lifting/ holding weight

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29
Q

small motor unit

A

innervates only a few muscle fibres
fine control more precision
finger muscles for manipulating objects

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30
Q

upper motoneurones

A

cerebral motor cortex/ brain stem
command and control
basis of voluntary control for movement

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31
Q

interneurones in spinal chord

A

excitatory and inhibitory
important for spinal movement programmes

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32
Q

muscle spindle

A

receptor type
intrafusal fibres in parallel w extrafusal fibres
innervated by 1a afferents going to spinal chord

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33
Q

extrafusal muscle fibres

A

do work of contraction

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34
Q

golgi tendon organ

A

receptor type in series w extrafusal fibres

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35
Q

1a afferent fibre of muscle spindle receptor

A

carries output signal of receptor to spinal chord

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36
Q

gamma motorneurones in controlling muscle spindles

A

alpha-gamma coactivation
keeps spindle firing constant and in operating range even though muscle contracts

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37
Q

golgi tendon organs

A

activated by muscle tension
innervated by 1b nerve afferents

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38
Q

types of movement

A

reflex (simple movement)
voluntary (complex/ may be learned)
rythmic (initiated and terminated by conscious control, automatic pattern in spinal chord)

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39
Q

reflexes

A

one sensory and one motor neurone reflex arc
spinal/ cranial origin
monosynaptic/ polynaptic

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40
Q

stretch reflex

A

monosynaptic> maintains contraction w increased load

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41
Q

golgi tendon reflex

A

protection against excessive load for control of posture

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42
Q

voluntary control of movement

A

brain pathways control alpha motoneurones in spinal chord
cerebral cortex > planning, coordinating and initiating
basal ganglia> planning and selection of movement
cerebellum > fine-tunes movement

43
Q

sound

A

defined by frequency/ amplitude

44
Q

P

A

peak pressure for a particular sound

45
Q

Pref

A

reference pressure

46
Q

each 1dB step

A

pressure increasing by a factor of 10^1/20

47
Q

dB threshold for hearing damage

A

90dB

48
Q

outer ear

A

pinna
externalisation of sounds/ localisation of sounds in vertical plane/ acoustic gain due to ear canal resonance

49
Q

middle ear

A

air filled
equal pressure either side of tympanic membrane
impedance transformer
overcomes air fluid mismatch ossicles acting as levers/ area of tympanic membrane greater than stapes footplate

50
Q

endolymph vs perilymph

A

endo ^K+
peri ^Na+

51
Q

human ear hair cells

A

one row of inner hair cells 3500
~3 rows of outer hair cells 12,000
stereocilia at tips > bend in response to pressure changes

52
Q

separation of sound frequencies in cochlea

A

travelling wave from base> apex
max displacement position depends on sound frequency

53
Q

frequency analysis by cochlea

A

upon entrance, basilar membrane vibrates, travelling up basilar from base to apex, max displacement depending on frequency, low freq max displacement at cochlea apex and high freq max displacement at base
basilar membrane displacement excites hair cells

54
Q

inner hair cell excitation

A

transmitter release/ excitation of auditory nerve fibres
stereocilia bend toward longest, K+ entry and depolarisation, Ca2+ entry and transmitter release> nerve fibre activation
stereocilia bend toward shortest, no K+ entry> hyperpolarisation no transmitter

55
Q

cochlea filters by frequency in 2 ways:

A
  1. neurone responds best to one frequency
  2. each location along cochlea amplifies one frequency
56
Q

outer hair cells

A

change length w stereocilia bending in response to sound stimulation
prestin (motor protein) driven
inject energy and amplify basilar membrane movement
*ototoxic drug damage

57
Q

basilar membrane motion amplification

A

elongation and shortening of outer hair cells ^basilar membrane displacement > enhanced hearing sensitivity and frequency selectivity

58
Q

coding sound frequency steps

A
  1. place code (tonotopic organisation)
  2. time code (phase locking for low frequency sounds)
59
Q

tonotopic organisation

A

auditory system tracking where info originated on basilar membrane within processing centres

60
Q

phase locking

A

synchronisation of firing to peaks in wave-form of low frequency

61
Q

1/period

A

frequency

62
Q

auditory nerve

A

connects cochlea to brain
first synapse = cochlear nucleus

63
Q

sound localisation

A

vertical plane > interactions of sound on pinna
horizontal plane >interaural differences in sound wave timing and frequency

64
Q

interaural sound cues for sound localisation

A

all sounds > difference in sound onset time between the two ears
long, continuous sounds> difference in phase of sound between 2 ears

65
Q

interaural time difference location

A

path difference
low f sound <15000Hz
wave takes longer to reach far ear> phase difference
high f sound >15000Hz
ambiguous phase difference

66
Q

localizing high frequencies by interaural intensity differences

A

head casts sound shadow for high f
brain detects difference in intensities
long wavelength relative to obstacle diffracted

67
Q

sound localization in elevation

A

interference between sound waves striking pinna and going straight into auditory canal
detected in brain auditory pathway

68
Q

cochlear implant

A

electrical activation of cochlear nerve fibres by electrode array inserted into cochlea

69
Q

cornea

A

refracts light to bring into focus in the retina

70
Q

lens

A

accommodation and adjusting refractive property of eye
more refraction if closer to bring into focus

71
Q

iris

A

pigment detects eye color
circular/ radial muscles controlled by autonomic ns adjusts pupil diameter according to light levels/ emotional signals

72
Q

pupil

A

opening allows light entry

73
Q

retina

A

layer at back of eye w photoreceptors/ horizontal cells/ bipolar cells/ amacrine cells/ ganglion cells/ nerve fibres
temporal > near temple
nasal> toward nose

74
Q

visual field of eye

A

covers 150 degrees

75
Q

ciliary muscles role in accomodation

A

lens flattened for distant vision/ rounded for near vision
contraction allows zonulas of zin to slacken, lens expands and becomes more thickened
weakens w age

76
Q

emmetropia

A

normal focussing

77
Q

myopia

A

short-sighted
too much focal power for length > light rays converge in front of retina

78
Q

hyperopia

A

long-sighted
too little focal power for length
light rays converge behind retina

79
Q

foveal pit

A

fovea cells in upper layer of retina
pushed aside to allow light to photoreceptors, regions of high acuity

80
Q

fovea

A

pit of centre of macula
central part of visual field
max acuity area
highest density of cone receptors, colour vision

81
Q

blind spot/ optic disc

A

region where nerve fibres/ blood vessels leave the eye

82
Q

retina organisation

A

pigment epithelium#
2 types of photoreceptors

83
Q

pigment epithelium

A

cells at retina back with photoreceptors embedded
contain melanin black pigment
absorbs light preventing scattering stray light

84
Q

2 photoreceptor types

A

rod (scotopic vision/ low light levels)
rod (photopic region/ high light levels

84
Q

2 photoreceptor types

A

rod (scotopic vision/ low light levels/ 20*more than cones)
cones (photopic region/ high light levels)

85
Q

3 types of cone photoreceptors

A

sensitive to long (red)/ medium (green)/ short (blue) wavelengths
highest acuity
enable colour vision

86
Q

threshold

A

1/ sensitivity

87
Q

dark adaptation

A

moving from bright to low light, cones not sensitive and rods are bleached
rod recovery w visual sensitivity

88
Q

light sensitive photopigments in rods and cones

A

rods> rhodopsin
cones> 3 different wavelength sensitive pigments

89
Q

rhodopsin

A

opsin protein + 11-CIS retinal
bound together in dark
conformational chage upon light exposure
> bleaching

90
Q

rod channels in dark

A

cyclic GMP levels high, keep Na+ channel open
Na+ current in> K+ current out
rod depolarised to -40mV and transmitter released

91
Q

rid channels in light

A

rhodopsin light breaching activates G protein/ transducin
cGMP production decrease so Na+ channels close
hyperpolarisation to -70mV
less transmitter release

92
Q

visual pathway

A

retina> lateral geniculate body> visual cortex> dorsal/ ventral stream

93
Q

photoreceptors function

A

releases glutamate in dark, exciting/ inhibitting bipolar cells

94
Q

bipolar cells function

A

excite/ inhibit retinal ganglion cells

95
Q

ganglion cells

A

form optic nerve fibres
centre surround organisation due to horizontal connections> contrats at edges of visual objects

96
Q

receptive field

A

retinal patch where light excites to fire impulses

97
Q

cone ganglion

A

centre surround organisation fed by different cone types:
red> green
blue> yellow
white light> weak firing

98
Q

nasal vs temporal fibre routes

A

nasal fibres cross at optic chiasm
temporal fibres remain uncrossed, stay on same side
L eye temporal/ R eye nasal go to left LGN and cortex
R eye temporal and L eye nasal got to tight LGN and cortex

99
Q

lateral geniculate body

A

per visual field site w contralateral/ ipsilateral layers keeping projections from each eye separate
3 cell types for 3 layer types
topographic mapping of visual world

100
Q

visual cortex

A

5 areas V1 (primary) to V5 (MT)
forward projections from V1 to higher cortical areas

101
Q

primary visual cortex

A

topographic mapping
cortical= centre of vision

102
Q

selective responses of neurones in eye

A

simple cell receptive field> overlapping inputs from LGN neurones
complex neurones in cortex sensitive to specific orientation of stimulus

PSC1002- Physiology (8 decks)

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