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Neuroscience (1206) > Motor Unit Recruitment > Flashcards

Motor Unit Recruitment Flashcards

1
Q

Features of muscle contraction can be demonstrated by eliciting single muscle __________

A

Twitches

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2
Q

What are some characteristics of muscle contractions

A

Involuntary
Visible under the skin
Arises from spontaneous discharge of a bundle of skeletal muscle fibers

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3
Q

In the latent period of a single fiber contraction, there is a delay of how much

A

1-2ms

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4
Q

What occurs in the latent period of a single fiber contraction

A 
Impulse travels along sarcolemma and down the t-tubules to sarcoplasmic reticulum (traids)
Ca is released and binds to troponin
Actin active site is exposed 
Myosin binds to actin
Tension is observed
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5
Q

How long is the contraction period of a single fiber contraction

A

10-100 ms

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6
Q

What occurs in the contraction period of a single fiber contraction

A

Tension rises as cross-bridges swivel and pull actin filaments towards the M line
Sarcomere length shorten

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7
Q

How long is the relaxation period of the single fiber contraction

A

10-100ms

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8
Q

What occurs in the relaxation period of a single fiber contraction

A

Muscle relaxes as tension decreases with unflexing of myosin heads and calcium sequestration
Sarcomere length returns to its original length

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9
Q

What are the two ways in which muscle can contract

A

Isometric contraction, Isotonic Contraction

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10
Q

What does isometric contraction involve

A

Maintenance of constant muscle length

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11
Q

True or false, isometric contraction involves a contracted muscle against a load as it is unable to shorten because load is great

A

True

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12
Q

In Isometric Contraction, Energy is released as _______ rather than through performance

A

Heat

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13
Q

Give examples of isometric contraction

A

Pushing against a wall
Holding a weight in fixed position
Holding a stack of books
Body building Pose

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14
Q

Isotonic contraction, involves maintenance of ________

A

Constant muscle tension

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15
Q

True or false, Isotonic Contractions involve contracted muscle against a load due to the muscles maximal force of contraction exceeding the total load on the muscle

A

True

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16
Q

True or false, in isotonic contraction, muscle shortens in length (concentric), or lengthens (eccentric)

A

True

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17
Q

Give examples of isotonic contraction

A

Bicep curls, swimming, cycling, running

18
Q

What is the term given to the adding of individual twitch contractions to increase the intensity of overall muscle contract

A

Summation

19
Q

What are the two ways in which summation occurs

A 
Multiple fibers (motor unit) summation
Frequency (wave) summation
20
Q

What type of summation occurs when there is an increasing number of motor units contracting simultaneously

A

Multiple fiber (motor unit) summation

21
Q

What type of summation occurs when there is an increase in the frequency of contraction

A

Frequency wave summation

22
Q

True or false, frequency summation occurs when there is a series of twitch contractions occurring one after the other at low frequency of stimulation

A

True

23
Q

Frequency summation leads to

A

Treppe (the staircase effect)

Tetany/tetanization/tetanus

24
Q

How does tetany arise

A

When enough calcium ions are maintained in the muscle sarcoplasm, even between APs, so that full contractile state is sustained without allowing any relaxation between the APs

25
Q

What is treppe

A

Gradual increase in the strength of a muscle contraction to a plateau following rapidly repeated stimulation after a quiescent period

26
Q

True or false, When a muscle begins to contract after a long period of rest, it’s initial strength of contraction may be as little as one half of its strength to 10 to 50 muscle twitches later

A

True

27
Q

What is the primary cause of treppe ie the staircase effect

A

Increasing Ca2+ in the cystol because of the release of more and more ions from the SR with each successive muscle AP
Failure of SR to recapture the ions immediately

28
Q

True or false, fatigue increases almost directly proportional to the rate of deletion of glycogen in the muscle

A

True

29
Q

What causes muscle fatigue

A

Prolonged and strong contraction of muscles

30
Q

According to Columbia university, what is the cause of fatigue

A

Calcium leaking into the muscle cells

31
Q

True or false, treppe can lead to fatigue

A

True

32
Q

If blood flow is interrupted while a muscle is contracting, almost complete muscle fatigue occurs within _________ minutes, due to a low supply of ________

A

1 or 2 minutes, oxygen

33
Q

What can muscles provide alterations in, in order to better suit the function that is required

A 
Diameter 
Length
Strength 
Vascular supply 
Type of muscle fibers
34
Q

What is muscle hypertrophy

A

When the total muscle mass increases due to an increase in size of fibers

35
Q

I’m fiber Hyperplasia, though rare may arise in _____

A

Increase in fiber number

36
Q

In Denervation sensitivity, there is promoted expression of _________ receptors on the sarcolemma

A

Nicotiinc acetylcholine receptors

37
Q

True or false, rigor Mortis occurs when muscle fibers are completely depleted of ATP

A

True

38
Q

True or false, in rigor mortis, nearly all the myosin heads are attached to actin but in a fixed abnormal and resistant manner

A

True

39
Q

Muscles remain in rigor until the muscle proteins deteriorate in _________, this is as a result from ________

A

15-25 hours later, Enzymic autolysis

40
Q

True or false, temperature increases the speed of the effects of rigor mortis

A

True

Neuroscience (1206) (17 decks)

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