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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
synergists / antagonists
synergists> muscles pulling in same direction antagonists> muscles pulling in opposite directions
26
neurones innervating muscle
large neurones alpha motoneurones in ventral horn of spinal chord
27
motor unit
motoneurone and muscle fibres it innervates
28
large motor unit
innervates many muscle fibres strong force and little precision lifting/ holding weight
29
small motor unit
innervates only a few muscle fibres fine control more precision finger muscles for manipulating objects
30
upper motoneurones
cerebral motor cortex/ brain stem command and control basis of voluntary control for movement
31
interneurones in spinal chord
excitatory and inhibitory important for spinal movement programmes
32
muscle spindle
receptor type intrafusal fibres in parallel w extrafusal fibres innervated by 1a afferents going to spinal chord
33
extrafusal muscle fibres
do work of contraction
34
golgi tendon organ
receptor type in series w extrafusal fibres
35
1a afferent fibre of muscle spindle receptor
carries output signal of receptor to spinal chord
36
gamma motorneurones in controlling muscle spindles
alpha-gamma coactivation keeps spindle firing constant and in operating range even though muscle contracts
37
golgi tendon organs
activated by muscle tension innervated by 1b nerve afferents
38
types of movement
reflex (simple movement) voluntary (complex/ may be learned) rythmic (initiated and terminated by conscious control, automatic pattern in spinal chord)
39
reflexes
one sensory and one motor neurone reflex arc spinal/ cranial origin monosynaptic/ polynaptic
40
stretch reflex
monosynaptic> maintains contraction w increased load
41
golgi tendon reflex
protection against excessive load for control of posture
42
voluntary control of movement
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
sound
defined by frequency/ amplitude
44
P
peak pressure for a particular sound
45
Pref
reference pressure
46
each 1dB step
pressure increasing by a factor of 10^1/20
47
dB threshold for hearing damage
90dB
48
outer ear
pinna externalisation of sounds/ localisation of sounds in vertical plane/ acoustic gain due to ear canal resonance
49
middle ear
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
endolymph vs perilymph
endo ^K+ peri ^Na+
51
human ear hair cells
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
separation of sound frequencies in cochlea
travelling wave from base> apex max displacement position depends on sound frequency
53
frequency analysis by cochlea
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
inner hair cell excitation
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
cochlea filters by frequency in 2 ways:
1. neurone responds best to one frequency 2. each location along cochlea amplifies one frequency
56
outer hair cells
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
basilar membrane motion amplification
elongation and shortening of outer hair cells ^basilar membrane displacement > enhanced hearing sensitivity and frequency selectivity
58
coding sound frequency steps
1. place code (tonotopic organisation) 2. time code (phase locking for low frequency sounds)
59
tonotopic organisation
auditory system tracking where info originated on basilar membrane within processing centres
60
phase locking
synchronisation of firing to peaks in wave-form of low frequency
61
1/period
frequency
62
auditory nerve
connects cochlea to brain first synapse = cochlear nucleus
63
sound localisation
vertical plane > interactions of sound on pinna horizontal plane >interaural differences in sound wave timing and frequency
64
interaural sound cues for sound localisation
all sounds > difference in sound onset time between the two ears long, continuous sounds> difference in phase of sound between 2 ears
65
interaural time difference location
path difference low f sound <15000Hz wave takes longer to reach far ear> phase difference high f sound >15000Hz ambiguous phase difference
66
localizing high frequencies by interaural intensity differences
head casts sound shadow for high f brain detects difference in intensities long wavelength relative to obstacle diffracted
67
sound localization in elevation
interference between sound waves striking pinna and going straight into auditory canal detected in brain auditory pathway
68
cochlear implant
electrical activation of cochlear nerve fibres by electrode array inserted into cochlea
69
cornea
refracts light to bring into focus in the retina
70
lens
accommodation and adjusting refractive property of eye more refraction if closer to bring into focus
71
iris
pigment detects eye color circular/ radial muscles controlled by autonomic ns adjusts pupil diameter according to light levels/ emotional signals
72
pupil
opening allows light entry
73
retina
layer at back of eye w photoreceptors/ horizontal cells/ bipolar cells/ amacrine cells/ ganglion cells/ nerve fibres temporal > near temple nasal> toward nose
74
visual field of eye
covers 150 degrees
75
ciliary muscles role in accomodation
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
emmetropia
normal focussing
77
myopia
short-sighted too much focal power for length > light rays converge in front of retina
78
hyperopia
long-sighted too little focal power for length light rays converge behind retina
79
foveal pit
fovea cells in upper layer of retina pushed aside to allow light to photoreceptors, regions of high acuity
80
fovea
pit of centre of macula central part of visual field max acuity area highest density of cone receptors, colour vision
81
blind spot/ optic disc
region where nerve fibres/ blood vessels leave the eye
82
retina organisation
pigment epithelium# 2 types of photoreceptors
83
pigment epithelium
cells at retina back with photoreceptors embedded contain melanin black pigment absorbs light preventing scattering stray light
84
2 photoreceptor types
rod (scotopic vision/ low light levels) rod (photopic region/ high light levels
84
2 photoreceptor types
rod (scotopic vision/ low light levels/ 20*more than cones) cones (photopic region/ high light levels)
85
3 types of cone photoreceptors
sensitive to long (red)/ medium (green)/ short (blue) wavelengths highest acuity enable colour vision
86
threshold
1/ sensitivity
87
dark adaptation
moving from bright to low light, cones not sensitive and rods are bleached rod recovery w visual sensitivity
88
light sensitive photopigments in rods and cones
rods> rhodopsin cones> 3 different wavelength sensitive pigments
89
rhodopsin
opsin protein + 11-CIS retinal bound together in dark conformational chage upon light exposure > bleaching
90
rod channels in dark
cyclic GMP levels high, keep Na+ channel open Na+ current in> K+ current out rod depolarised to -40mV and transmitter released
91
rid channels in light
rhodopsin light breaching activates G protein/ transducin cGMP production decrease so Na+ channels close hyperpolarisation to -70mV less transmitter release
92
visual pathway
retina> lateral geniculate body> visual cortex> dorsal/ ventral stream
93
photoreceptors function
releases glutamate in dark, exciting/ inhibitting bipolar cells
94
bipolar cells function
excite/ inhibit retinal ganglion cells
95
ganglion cells
form optic nerve fibres centre surround organisation due to horizontal connections> contrats at edges of visual objects
96
receptive field
retinal patch where light excites to fire impulses
97
cone ganglion
centre surround organisation fed by different cone types: red> green blue> yellow white light> weak firing
98
nasal vs temporal fibre routes
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
lateral geniculate body
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
visual cortex
5 areas V1 (primary) to V5 (MT) forward projections from V1 to higher cortical areas
101
primary visual cortex
topographic mapping cortical= centre of vision
102
selective responses of neurones in eye
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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