Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MSK/Derm > SM 224: Muscle Physiology and Mechanics > Flashcards

SM 224: Muscle Physiology and Mechanics Flashcards

You may prefer our related Brainscape-certified flashcards:
Dermatology Board Prep flashcards
1
Q

Are muscle fibers single cells or multiple cells?

A

Muscle fibers = single myocyte

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Do muscle fibers have 1 nuclei or many nuclei?

A

Muscle fibers are multi-nucleated single cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the thick filament?

A

Myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the thin filament?

A

Actin, which is bound by Troponin and Tropomyosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the 2 domains of the thick filament and what are their functions?

A

Myosin has an S1 and an S2 domain.

S1: Actin-binding ATPase and lever for movement
S2: connects Myosin filament to other Myosin filaments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does ATP contribute to the crossbridge cycle?

A

ATP binding allows for the dissociation of the actin-myosin complex - rigor mortis arises from lack of ATP

ATP is hydrolyzed to reorient the Myosin S1 head

Powerstroke occurs when ADP + Pi are released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which molecule is required for the Powerstroke, ATP or ADP?

A

ADP + Pi are released after ATP is cleaved in an earlier step for the Powerstroke to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the “molecular motor”?

A

The powerstroke associated with the release of ADP + Pi

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What 4 factors determine how many cross bridges are attached at any given time?

A

The 4 factors that set the number of attached cross bridges are:

CNS mediated Ca levels in the Myocyte
Filament overlap between Actin + Myosin
Speed of movement of filaments past eachother
Speed of cross bridge cycling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How does the CNS control motor unit contraction force?

A

The CNS releases a single impulse via the Ventral horn of a motor neuron, which depolarizes an entire motor unit at the Neuromuscular Junction

Depolarization raises intracellular Ca levels and the strength of contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How is CNS stimulation different in a twitch and sustained contraction?

A

In a twitch, CNS stimulation is a single AP which leads to brief activity

In sustained contraction, CNS stimulation is multiple AP’s, with each AP raising Ca levels and strength of contraction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What sets the strength of the CNS-mediated component of muscle contraction?

A

The frequency of AP’s sets the strength of CNS-mediated muscle contraction as the calcium influx experiences a tetany

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does filament overlap set the strength of contraction?

A

If the filaments are overly stretch and too far apart, there is no overlap as the Myosin heads do not face the Actin filaments = no contraction force

If the filaments are too close, the filaments can’t slide past eachother = no contraction force

Moderate length has ideal overlap and room for movement = max contraction force

Different muscles have different degree of overlap at rest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does filament movement speed effect contraction force?

A

Higher filament sliding speed corresponds with faster movement, but may faster than the rate of crossbridge formation, leading to less crossbridge formation and lowering contraction strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does the speed of the crossbridge cycle effect contraction force?

A

Faster rates of crossbridge cycling allow for more contractions and lead to higher contraction force

Rate of crossbridge cycling depends on the various isozymes of myosin involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the force-stimulus frequency of muscle?

A

Average force increases as number of motoneuron AP’s per time increases, resulting in a function that increases to a maximum force = tetany

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the force-length relationship of muscle?

A

Alteration in filament overlap in different limb positions and muscle lengths leads to altered number of crossbridges and different contraction strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the force-velocity relationship of muscle?

A

Number of attached cross-bridges depends on the speed of limb movements (inversely)

Also, force decreases when shortening a muscle and increases when lengthening a muscle due to sarcomere destruction with lengthening

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Does force decrease with shortening or lengthening?

A

Shortening a muscle decreases force

Lengthening a muscle destroys sarcomeres and ironically increases force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the sources of “stiffness” in a muscle?

A

“Passive stiffness” of a Sarcomere due to titin
“Elastic stiffness” due to connective tissue and tendons
“Contractile Elasticity” due to force-length overlap

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Why is ATP not the primary energy storage molecule in muscle?

A

ATP is highly unstable and cannot be stored in large amounts for large periods of time

Convert other things to ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How might energy sources for muscles differ?

A

Energy sources differ in:

Mobilization time
Maximum rate of energy production
Total amount stored

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What types of pathways are used for high force and fast movement?

A

Anaerobic pathways

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the anaerobic pathways?

A

ATP
CP
Anaerobic Glycolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the mobilization time, amount stored, and rate of energy production of ATP to power muscle contraction?

A

Mobilization time: instantaneous (no conversion needed)
Amount stored: very little
Power: highest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How long could ATP alone supply contraction?

A

5s max

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the mobilization time, amount stored, and rate of energy production of CP to power muscle contraction?

A

Mobilization time: very fast (CP gives P to ADP via CPK)
Amount stored: more than ATP, but still very little
Power: high, not as much as ATP

28
Q

How long could CP alone supply contraction?

A

15s max

29
Q

Describe the mobilization time, amount stored, and rate of energy production of Anaerobic Glycolysis to power muscle contraction?

A

Mobilization time: 5-30s
Amount stored: Glycogen could last up to 2 hours
Power: Less than ATP/CP but more than Aerobic Glycolysis

30
Q

What is Anaerobic Glycolysis and why is it slower than ATP/CP?

A

Anaerobic Glycolysis is the conversion of Glycogen to Pyurvate via Glycogen Phosphorylase and PFK

Takes multiple enzymes to release Glucose from Glycogen and convert it into Pyruvate

Also generates an O2 debt

31
Q

What pathways do longer activities require?

A

Aerobic pathways

32
Q

What are the aerobic pathways?

A

Aerobic Glycolysis

Fatty Acid Beta Oxidation

33
Q

What is Aerobic Glycolysis?

A

The conversion of Pyruvate to ATP via the TCA and OxPhos

Uses enzymes like SDH and NADH

34
Q

Describe the mobilization time, amount stored, and rate of energy production of Aerobic Glycolysis to power muscle contraction?

A

Mobilization time: 30s-120s (longer than Anaerobic)
Amount stored: Glycogen could last up to 2 hours
Rate of energy production: less than Anaerobic Glycolysis

35
Q

Why does Aerobic Glycolysis take longer than Anaerobic Glycolysis?

A

Aerobic Glycolysis is O2 dependent and requires time for O2 to be delivered, so Anaerobic Glycolysis is faster

36
Q

Describe the mobilization time, amount stored, and rate of energy production of Beta Oxidation to power muscle contraction?

A

Mobilization time: 20-60min
Amount stored: a lot
Rate of energy production: slowest of all pathways

37
Q

What pathway has the least power?

A

Power = rate of energy production

Beta Oxidation has the lowest power

38
Q

Does the CNS control single fibers or several fibers?

A

Each CNS Motor Neuron controls several muscle fibers

Motorn Neuron + Muscle Fibers = Motor Unit

39
Q

What properties differentiate the types of motor units?

A

Contraction speed
Fatigue resistance
Maximum force

40
Q

What sets the contraction speed of a motor unit?

A

Myosin cycle speed

41
Q

What sets the fatigue resistance of a motor unit?

A

Energy pathway utilized

42
Q

What sets the maximum force of a motor unit?

A

Number and size of muscle fibers per unit, which relates to total number of cross bridges

43
Q

What type of motor unit is Slow?

A

Type I

44
Q

What type of motor unit is Fast Fatigue Resistant?

A

Type IIA

45
Q

What type of motor unit is Fast Fatiguable?

A

Type IIX

46
Q

Are motor unit populations in muscles heterogenous?

A

Yes, all muscles have a mix of all 3 types of motor units that matches their function

47
Q

If Myosin heads are constantly contracting, why isn’t a contraction force being generateed?

A

For a contraction force to be generation, attachment of cross bridges must occur, which only happens when the CNS triggers Ca release in the myocyte via APs

48
Q

Does the CNS control entire muscles to mediate contraction?

A

No, the CNS controls motor units, which together make an entire muscle that can contract

49
Q

What factors set muscle energy utilzation?

A

Intensity and duration of exercise

50
Q

What mechanical property describes muscles?

A

“Spring-like”

51
Q

What signaling molecule is needed for Myosin heads to bind Actin filaments?

A

Calcium release from the SR

52
Q

Why is a single AP from the CNS motor neuron not sustained?

A

The SR actively pumps the Ca released into the cytosol back into itself via SERCA

53
Q

Which domain of the Myosin head is mobile and moves during contraction?

A

S1

54
Q

Do the thick filaments in a sarcomere contract in the same or opposite direciotns?

A

Thick filaments contract in opposite directions, resulting in greater filament overlap and a shorter sarcomere

55
Q

Do muscle fibers naturally contract?

A

Yes, this is why slowly lowering a weight allows for lots of muscular hypertrophy, since it challenges the natural tendency of the Sarcomere

56
Q

What are the steps in a muscle fiber twitch?

A

CNS Motor neuron releases a single AP
AP travels down Axon
AP arrives at NMJ
AP depolarizes group of myofibrils in motor unit via Ca release
Ca release allows for Actin-Myosin crossbridges to form
Muscle twitch occurs and ends due to SERCA reuptake

57
Q

How does conduction speed change along the muscle fiber pathway?

A

Conduction speed decreases with every step of the conduction pathway

58
Q

What CNS property sets the maximum force of muscle contraction?

A

AP frequency from the Motor Neuron determines intracellular Ca levels and number of cross bridges, therefore it sets the maximum force of contraction

59
Q

What is a tetonic frequency?

A

Frequency of AP’s that maxes contraction force; higher frequency AP’s result in the same force

60
Q

How does muscle size set the number and density of motor units?

A

Bigger muscle
= More motor units
= More muscle fibers per motor unit

61
Q

How do motor units mediate cross-talk between motor neurons?

A

They don’t - each motor neuron only communicates with its own myofibrils

62
Q

Describe the force output and contraction duration of a Slow motor unit?

A

Low force output for long duration

63
Q

Describe the force output and contraction duration of a Fast Fatigue Resistant motor unit?

A

Medium force output for medium duration

64
Q

Describe the force output and contraction duration of a Fast Fatigable motor unit?

A

High force output for short duration

65
Q

What fatigues first, a large motor unit or a small motor unit?

A

Large motor units fatigue first

MSK/Derm (46 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions