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258 - physiology > LAB EXAM LAB 1: MU recruitment > Flashcards

LAB EXAM LAB 1: MU recruitment Flashcards

1
Q

where does an AP travel when a motor neuron is deplozariz

A

down axon to neuromuscular junction

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2
Q

what NT is released at the NMJ and where

A

acetylcholine in synaptic cleft

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3
Q

what does the relased of scetyl choline due

A

actiavtes acetyl choline receptors which allow the muscle membrane adjucatent to the end plate to reach its threshold

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4
Q

what is the result of a muscle end plate reaching threshold

A

generation of Ap in muscle fiber and the contraction of the fiber

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5
Q

what is another name for contraction

A

tweitch

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6
Q

what is a motor unit

A

a motor neuron, its aox and all the muscle fibers taht the axon innervates

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7
Q

true or false: the MU is the largest functional unit in the neuromuscular systyem

A

false

it is the smallest therefore the smallest part of the ystem that can be controlled independatnylu

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8
Q

true or false: msucles fibers cannot be activatied independatnly

A

true

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9
Q

a single otor neuron innervates 1 or several muscel fibers

A

several

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10
Q

each muscle fiber is innervated by 1 or more motor neuron nervre ending

A

only 1 motor neurons nerve ending

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11
Q

what are some different chracterties of muscle fibers and MU

A

speed of contraction, max force production

resistance to fatigue

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12
Q

different motor units have the same or different innervation ration

A

varying innervation ration

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13
Q

muscles used for fine dexterous movement (hand, eye) have low or high innervation

A

low innervation ration

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14
Q

what dose it mean to have a low innervation ration

A

one motor neuron only innervaties a few muscle fibers

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15
Q

muscles used for foreceful and ballistic movements (like quads) have a low or high innervation ration

A

high innervation radio

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16
Q

what does it mean to have a high innervation ration

A

one motor neuron innrvations many muscle fibers

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17
Q

how are wide reanges of movements acheived

A

by varying the number of active motor units which then cahnges the amount of force produced

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18
Q

what are the 3 factors that determine degress of skeletal muscle contraction

A

1) degree of muscle strength (length tension relation)
2) the acvation of desrired number of motor units (intensity of activation)
3) the frequency of motor neuron impulses in each motor unit (frequency of activation)

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19
Q

the sequential activation of motor units to perform a designmated task is called …

A

motor unit recruitment

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20
Q

explain length tension relationship

A

the degree of tension developped is determined by the overlap between actin/myosin
too much overlap or not enough overlap does not allow enough force to be generalted
=THERE IS AN OPTIMAL OVERLAP LENGTH

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21
Q

what are muscles recruited according to

A

size princicple: hennemans sixe principle

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22
Q

explain intensity (hennemans size principle)

A

motor units are recruited according to size (smallest motor units actviated first)

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23
Q

what is the activtion freq for maintaening posture

A

20 pulses/sec

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24
Q

activation freq for walking

A

Walking

• 30 pulses/sec

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25
Q

activation freew for full out sprint

A

Full-out sprint (measured in quad)

• 75 pulses/sec

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26
Q

rtue or false: the electical impulse generated and conducted by each fiber is very strong

A

false, very weak (100 microvolts)

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27
Q

explain how this small impulse can be detected by a pair of electrons

A

many fibers conduction simultaneously indice voltage differences in overlying skin that are large enough to be detected by a pair of surfrace electrodes

28
Q

what is the def of electromyography

A

the detection, amplicafication and recording of these changes in skin voltage produced by activation of underlying msucle contracttion

29
Q

what is the recording of electromyography called

A

electromyogram (EMG)

30
Q

true or faale: EMG is a direct measure of muscle force

(and whyP

A

false it is not a direct measure of force
since depolarization triggers contraction, the AP precede tje contraction
(ie. EMG is recorded priot to any force generation mecanism)

31
Q

what is the force measured with and in what units in the lab

A

kg by handgrip dynamotor

32
Q

what is the def of sksetlal muscle fatigue

A

decrease in muscles ability to generate force

33
Q

what is muscle fatigue caused by

A

revversible depeletion of the msucle energy/field supply (ie. glycogen)

34
Q

when does fatigue occur

A

when muscle uses energy sources faster than they can be generated

35
Q

what is the onjective of the demo

A

show how increases intensity andfrequency of msucel stim effects force of muscle contraction produced

36
Q

what is the nerve used for the demo

A

median nerve at the wrist

37
Q

what are the single signal pulses appkied to the thenar muscle

A

50-70 v or more, 1 ms

38
Q

when is the demo ended

A

when the thenar muscle fully contacts (ie./ thumb flexion)

39
Q

what is the force of the demo of the thumb recorded by

A

transducer

40
Q

what is the actual procedure for demo

A

electrons placed on swabbed skin
place in transfucer

1) deliver single stimulat at 5 second intervales (causing a twitch)
voltage is increased until maximal stimulatm is verified (when there is no firther rise is twitch torque)
=shows how indivadual motor units are recruited by increase intensity of stim

2) muscle is stim with bursts of impulses (increasing freqnuencies= 3, 7,10,15
=showing how frequency of activation effects muscle force and how fluid locaomots actions are acheived via summation

41
Q

what does it indicatied when there is no fruther rise in twitch torque deteted

A

all motor units have neen actvated for that muscle (shows how indivadual motor units are recruited by increase intensity of stim)

42
Q

what is incomplete tentanus

A

muscle exhibits shorter and shorter contraction-relaxation cycles resulting in the summation of contractions. In this case, there is still time for partial muscle relaxation before the next stimulus.

43
Q

what is fused tetanus

A

there is no time for relaxation between stimuli, resulting in the fusion of individual contractions
into a single, smooth, total muscle contraction. This leads to fluidity of movement.

44
Q

unfused tetanus causes fluidity or movement

A

false, fused tetnus

45
Q

what does wave summation mean

A

there is no time to relax before next stitm is applied so force is :summated”
ie;: added to the previous one for increase in force

46
Q

what is the main difference between incomplete and completet teatnus

A

abundance of intra-cellular Ca++.

47
Q

explain CA and contraction for complete tetanus

A

With the decreased time between stimuli in complete tetanus, the Ca++ has less time to clear from the sarcoplasm.
=The resulting build-up of Ca++ leads to the sustained contraction and fluid
movement.

48
Q

when does treppe occur

A

muscle is repeatedly activated following a rest period, which leads to an
increase in tension with no wave summation
=The strength ofcontraction increases to a plateau.

49
Q

what is another name for treppe and what is the reason behind it

A

This phenomenon is also known as the “staircase effect” and

is thought to be due to increasing Ca++ in the cytosol.

50
Q

what is task 1 of the MU lab and its resultant objective

A

increasing clench force
Determine the relationship between the force
of muscle contraction and the intensity of EMG
activity (in dom and non dom)

51
Q

what is task 2 and its corresponding objectivw

A

continued clench at max force
Determine time to fatigue at 50% of maximum
clench force

52
Q

true or false: you can have jewelylry aand watches for experiement

A

false

53
Q

where are the 3 electrodes placed

A

over the belly of the felxor muscles (first distal to anticubilta fossa on medial side, 2) 10cm distal to sceond)

3) unlar styloi process (medial wrist, on bone)

54
Q

what is the function of the elcecttron placed on the ulnar styloid process

A

ground electode

55
Q

explain calibration

A

Zero the dynamometer and EMG, Provide max grip strength = 100%

=the system then determines an interval for
the tests

56
Q

explain task 1 (increasing clench force)

A

every ttwo seconds you are going to increase clench force to a certain level
test ends when max grip force is reached (nom and dom)

57
Q

explain task 2 (fatigue)

A

clench dyna for as long as you can and test stops when force level falls below 50% of maximal achieved

58
Q

what values to you get for task 1

A

force at peak (max foce)

59
Q

what values do you get for fatigue test

A

time to fagtigue

60
Q

what are 4 reasons to epxlain decline in strenght as one fatigues

A

A depletion of muscle glycogen (ATP) in prolonged intense activity leads to the inability of the contractile and metabolic processes of the muscle fibre to continue supplying the same work output.

  • Transmission of the nerve signal through the neuromuscular junction can diminish
    slightly after intense prolonged muscle activity, leading to muscular fatigue.
  • Interruption of blood flow leads to loss of nutrient supply and loss of oxygen, resulting in muscular fatigue within 1 to 2 minutes.
  • An increased level of blood and muscle lactate can impair the function of contractile proteins.
61
Q

what is NADH

A

NADH is short for Nicotinamide Adenine Dinucleotide. It is a derivative of vitamin B
(niacinamide) combined with a ribose (5 carbon sugar), a phosphate group and an adenine
=coenzyme (found in cytosol and mito)

62
Q

what is the role of NADH

A

The role of NADH in cellular metabolism is directly linked to the role of NAD+. These
compounds are the most important carriers of the H+ atoms that are released during the breakdown of energetic substrates. This breakdown occurs in order to produce ATP,

which subsequently transports the H+ to the respiratory chain of electrons located in the inner membranes of the mitochondrion. There, the H+ are relinquished to the electron acceptors of the respiratory chain. This process is a major component of aerobic metabolism

63
Q

what is the difference between FAD and NAD

A

NAD and FAD are both electron (hydrogen) carriers.

is that FAD is able to accept and carry 2 hydrogen ions, whereas NAD can only accept 1 hydrogen ion.

FAD cannot produce more ATP than NAD since NAD enters the ETC earlier
the more ATP can be produced.

every NADH molecule, 3 ATP
every FADH2 molecule, 2 (ATP

64
Q

what is the relationship between IMEG and force

A

as the transmission of the electrical nerve signals sent to the
muscle increases,
the force of the contraction produced by the muscles also increases
indicates that the subject’s muscles are responding well to the signals sent by the motor neurons.

65
Q

why is it possible the dom arm has a lower peak

A

The fact that the dominant arm is more efficient at sending out the signals and having the muscles contract at the corresponding force is most likely due to the fact that the dominant arm carries out all the very fine motor skills

non dom=better for ballistic

258 - physiology (21 decks)

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