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Motor Control > Stimulus Elicited Behaviour > Flashcards

Stimulus Elicited Behaviour Flashcards

1
Q

What is stimulus -elicited behaviour? 2

A

object/event ->animal->behaviour
behaviour that is produced as an involuntary and relatively immediate consequence of sensory stimulation: the behaviour is an involuntary response to the stimulation

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2
Q

eliciting stimulus

A

any stimulus that is effective at eliciting a particular behavioural response. such a stimulus is then an eliciting stimulus for that particular behaviour

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3
Q

Response latency

A

period of time that elapses between the onset of the stimulus and the onset of the (involuntary) response it elicits - too soon its spontaneous, too long its voluntary

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4
Q

2 ways a stimulus elicits a behavioural response

A

stimulus drive the response

stimulus releases the response

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5
Q

stimulus driven response

A

stimulus elicited behaviour in which the neural activity that causes the muslce contraction derives directly from that evoked by the eliciting stimulus in axons of sensory neurons - being poked - each time we stimulate receptor sensory neuron

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6
Q

stimulus released response

A

stimulus elicited behaviour where the neural activity that causes the muscle contractions does not derive from the eliciting stimulus. The activity is produced by a response generating mechanisms that generates it when it receives a signal derived from the eliciting stimulus - chicken running for cover - brief stimulus can elicit a continuous response

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7
Q

all or nothing for stimulated responses

A

once the response has been triggered - it will be executed to completion regardless of whether the elicitng stimulus persists or not

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8
Q

reflex

A

discrete action or period of sustained activity (possibly repetitive) that is produced as a direct, involuntary, and relatively immediate response to the stimulation of a specific pop. of sensory receptors

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9
Q

how do we lessen the effect of a reflex

A

brace ourselves when we know something is about to happen

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10
Q

autonomic responses vs skeletomotor behaviour

A

stimulus goes to sensory system - then either autonomic NS for cardiac and smooth for a autonomic response, or somatic NS for skeletal muslces for skeletomotor behaviors

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11
Q

elemental reflexes 2

A

components of complex, and goal directed reflexes
standard reflex in which the response is confined to a single, specific muscle and cannot be meaningfully divided into separate response components

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12
Q

Kandel - motor coordination

A

process of linking the contractions of many indeendent muslces so that they can act together and can be controlled as a single unit

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13
Q

Sir Charles Sherrington - early perspective of movement

A

simple reflexes are the basic units for movement; complex sequences of movements are produced by combining activity of simple reflexes

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14
Q

Contemporary perspective of movement

A

neural circuits that produce motor output are activated by centrally generated motor commands as required to produce adaptive movements

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15
Q

Spinal cord circuitry function - 3

A 
provides means of linking muslces together - synergistic activation of AG/ANT muscle pairs via reciprocal inhibition 
provide elementary patterns of behaviour - reflexes (simple and complex) without descending outputs (we dont need info from the brain 
permits regulation (modulation) of excitatory afferent input - reducing effectiveness and inhibition
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16
Q

2 methods to reduce effectiveness of excitatory inputs

A

presynaptic inhibition
postsynaptic inhibition
inhibiting cells before or after the synapse

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17
Q

3 ways of presynaptic inhibition

A

alters presynaptic membrane permeability and reduces probability of AP firing - subthreshold depolarization so when it gets depolarized its a smaller distance that it has to travel - determines the amount of neurotransmitters released
reduces the amount of neurotransmitter released at presynaptic terminal
selectively reduces effectness of synaptic inputs to postsynaptic membrane

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18
Q

2 ways of postsynaptic inhibition

A

inhibition occurs on postsynaptic cell body membrane - axosomatic
makes postsynatic neuron less sensitive to excitatory input due to membrane hyperpolarization

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19
Q

2 examples of postsynaptic inhibition

A

Ia- IN interneurons

renshaw cells

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20
Q

spinal reflex

A

any reflex mediated by neural mechanisms that are confined to the peripheral NS and spinal cord

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21
Q

spinal reflex is discovered from

A

decerebrate preperations - Sherrington’s cats where they isolated the brain from the spinal cord but still saw reflexes menaing there is no need for input from the brain

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22
Q

current perspective of reflex output

A

reflex output/motor response can be modified to meet task demands.

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23
Q

Reflex arc

A

a linked chain of individual neruons that connects a single sensory receptor to a single alpha MN

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24
Q

afferent neuron in a reflex circuit

A

convey stimulus detection

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25
Q

efferent neuron in a reflex circuit

A

induces muslce contraction

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26
Q

central processing unit in a reflex circuit

A

simple or complex

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27
Q

types of reflexes categorized by number of synapses

A

monosynaptic - just one
disynaptic - 2 - 1 interneuron
trisynaptic - 3 - 2 interneurons
polysynaptic - more than 3 - more than 2 interneurons

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28
Q

simple circuitry: interneurons (2) - where are they and what do they do?

A

neurons restricted to spinal cord

able to influence nearby neurons - propriospinal neurons

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29
Q

reflex latency and 3 components

A

time delay between stimulus and reaction
Delta Ta - time of afferent conduction
Delta Te - time of efferent conduction
- neuron type, length of fibre, health of neuron
Delta Tc (central delay) - central processing unit - 1-5ms
- number of synapses

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30
Q

MSR (5)

A

monosynaptic stretch reflex, stretch reflex, deep tendon reflex, T-reflex, myostatic reflex

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31
Q

MSR pathways

A

densely interconnected

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32
Q

LLoyd and Renshaw via intracellular recording - Neural circuitry - 4

A

Ia discharge - exitation homonymous - sensory and motor to the same muscle
Excitation homonymous and synergistic
inhibition antagonist
MST latency ~70ms quickest as a mono and most simple

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33
Q

reciprocal innervations

A

innervation to AG/ANT muscle gps from same neuron source - same Ia afferent goes to agonist and antagonist

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34
Q

reciprocal inhibition (2)

A

neuron source contribution to inhibition of muscle groups antagonistic to prime mover muscle groups
an effect of reciprocal innervation

35
Q

the stronger the stimulus - response?

A

the more vigorous the response

36
Q

reflex threshold

A

lowest strength of the eliciting stimulus that is capable of reliably eliciting the reflex response

37
Q

the longer the stimulus duration - response duration

A

longer

38
Q

the stronger the eliciting stimulus - latency

A

shorter

39
Q

natural reflexes inherit the properties of

A

elemental reflexes

40
Q

MSR gain

A

Spinal cord excitability

magnitude motor response relative to the magnitude of sensory stimulus - output:input

41
Q

MSR gain for the same magnitude of input i.e. muscle stretch

A 
high force (motor) output - high gain - throwing our glass of water over our shoulders 
low force (motor) output - low gain -
42
Q

Gain

A

effectiveness of reflex pathways

43
Q

Neural mechanisms of reflex gain - principle

A

reflex gain is set according to task demands

44
Q

3 contributing neural mechanisms that can provide explanation for a change in reflex gain?

A

fusimotor activity
presynaptic modulation
postsynaptic modulation

45
Q

how does fusimotor activity change reflex gain? - 5

A

Gamma MN regulate sensitivity of spindle to stretch
gamma activation will prestretch central regions of intrafusal fibres and alter their sensitivity to streth - gamma bias, fusimotor set, gamma drive
ensures AP firing at onset of stretch, during stretch, and stretch termination
same stimulus intensity - different AP firing
preloaded muscle provides earlier and more robust afferent response - theoretically, more fdbk

46
Q

postsynnaptic modulation

A

postsynaptic membrane (alpha MN) altered by direct input to alpha MN cell body - altering excitability of alpha MN pool

47
Q

3 potential contributing factors to absent or weak response of MSR gain

A

disorder of reflex circuit - sensory/motor axon or cell bodies, synaptic transmission disorder
“higher order” disorder - hyperactive pre/pose inhibition
peripheral disorder - muslce spindle receptor

48
Q

overactive response of MSR - potential diseases

A

Hyperactive MSR - quicker and larger in magnitude

high MSR gain - disorders of muslce tone (spasticity and rigidity)

49
Q

potential contribution factor of overactive response of MSR

A

caused by “high order” disorder (lesions) which removes descending inhibition - highest being spinal cord injuries

50
Q

spinal shock

A

no reflex the first day but overactive reflex after

51
Q

bottom line of reflex gain

A

spinal cord circuitry plays a major role in modulation of reflex gain

52
Q

excitability of spinal cord

A

“state” of alpha MN pools

53
Q

Spinal cord excitability provides insight into 2

A

potential for alpha MN to respond to sensory input
- types include real/sensory fdbk or imposed/electrical current
potential for alpha MN to receive descending drive - descending motor commands

54
Q

Does reflex gain change? or are alpha MN more/less receptive to excitation -2 ways

A

eliminate peripheral contribution to reflex gain - isolate central contribution
determine input:output ratio - Hoffman reflex/H reflex testing

55
Q

H reflex

A

Hoffman reflex - electrical analog of the stretch reflex

Motor response elicited by electrical stimulation of Ia afferent nerve - introduces AP into afferent nerve

56
Q

H reflex latency

A

~30ms - eliminating activation of muslce spindle which eliminates the fusimotor/generation of the AP and only travels on one side

57
Q

Principle of reflexive vs direct simulation of muscle fibres

A

stimulation intensity dictates neuron activation - large fibre axons activated at low stimulation intensity

58
Q

at low stim intensity

A

Ia afferent recruitment leading to reflex-based motor response

59
Q

what happens when stimulation intensity increases?

A

recruitment of smaller neurons - alpha MN - direct stimulation of muscle fibres - M wave/response - latency of 3-8ms because it only has to travel along the remainder of the alpha MN - NOT reflexive

60
Q

Low stim intensity

A

no response

61
Q

increased stim intensity

A

Ia recruitment; H reflex

62
Q

higher increased stim intensity

A

Ia and Alpha MN recruitment - M-response and increased amplitude H-reflex

63
Q

higher higher increased stim intensity

A

M-wave amplitude increase due to MN recruitment - plateau when we see all of our MN fire
H-reflex amplitude decrease due to an electrical blockage

64
Q

electrical blockage

A

antidromic and orthodromic AP propagation following electrical stimulation
efferent axon orthodromic propagation = M-wave
antidromic propagation “blocks” orthodromic Ia propagation at axon hillock which blocks Ia induced efferent AP

65
Q

Who’s the monitor for stim intensity?

A

M-wave amplitude

66
Q

Neural mechanisms underlying alterations in H-reflex gain?

A

Clinical test of integrity of central mechanisms in altering excitability of alpha MN pool
voluntary muslce activation leads to postsynaptic excitation of agonist alpha MN pools - stim of Ia during voluntary activation will cause increased H-wave amp (due to Ia synaptic connection to excited alpha MN pools)

67
Q

H reflex + voluntary muslce activation

A

test effectiveness of central mechanisms for altering excitability of alpha MN pools

68
Q

What does it mean when the behaviour elicited happens too long, too short, or just right?

A

too long - voluntary response
too short - spontaneous/ coincidental
just right - involuntary reflex

69
Q

postsynaptic inhibition is what kind of synapse?

A

axoaxonic

70
Q

spinalised cats - 2

muscle stretch - 2

A

Charles Sherrington decerebrate preparation
- increased extensor tone
- heighten spinal reflexes
brisk muscle stretch - contraction of stretched muscle and relaxation of antagonist muscle

71
Q

presynaptic modulation

A

alters effectiveness of synaptic inputs to alpha MNs

72
Q

absent/weak response means

A

hypoactive MSR/low MSR gain

73
Q

constant stim intensity and H wave fluctuations

A

increase of H wave means means an increase in reflex gain, decrease means reflex modulation

74
Q

low stim vs high stim and what they activate

A

larger afferents vs smaller afferents and large efferents

75
Q

peripheral mechanisms of reflex gain

A

fusimotor

76
Q

central mechanisms of reflex gain

A

presynaptic and postsynaptic modulation

77
Q

stimulus duration is coded by - skin

A

cutaneous and subcutaneous mechanoreceptors which have a low threshold - high sensitivity

78
Q

sensory map

A

sensory homunculus

79
Q

stim vs blockade

A

if the stim remains the same, so will the blockade

80
Q

The function of the gamma motor system

A

Regulate sensitivity of muscle spindles for detecting stretch

81
Q

Stimulation intensity dictates?

A

Neuron activation - large fibre axons activated at low stim intensity

82
Q

Recurrent collateral of RENSHAW

A

Collateral of alpha MN that synapses with the RENSHAW cell itself

83
Q

Sustained rhythmic alteration does not depend on?

A

Supraspinal inputs

Motor Control (9 decks)

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