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MVS 340 FINAL > SKELETAL MUSCLE > Flashcards

SKELETAL MUSCLE Flashcards

1
Q

What percentage of body mass does skeletal muscle comprise?

A

~40%

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2
Q

What are the essential functions of skeletal muscle?

A

Posture, breathing, motion, and metabolic regulation.

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3
Q

What is sarcopenia?

A

Loss of muscle strength and mass due to aging.

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4
Q

What are satellite cells?

A

Muscle stem cells found in the basal lamina, needed for muscle repair and adaptation.

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5
Q

What are the two main types of skeletal muscle fibers?

A

Slow-twitch fibers (Type I) and fast-twitch fibers (Type II).

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6
Q

What is the primary metabolic difference between Type I and Type II fibers?

A

Type I fibers are oxidative, while Type II fibers are glycolytic.

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7
Q

What are the characteristics of Type I fibers?

A

High oxidative capacity, fatigue-resistant.

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8
Q

What are the characteristics of Type IIx fibers?

A

Low oxidative capacity, fatigable.

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9
Q

What is the size principle in muscle recruitment?

A

Smaller motor units are recruited first, followed by larger units as needed.

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10
Q

What happens during excitation-contraction coupling?

A

The brain signals muscle contraction, leading to calcium release and muscle shortening.

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11
Q

What is the all-or-none principle?

A

Once a stimulus triggers an action potential, all muscle fibers in the motor unit contract synchronously.

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12
Q

What are the two mechanisms to adjust muscle force?

A

Increased motor unit recruitment and increased frequency of motor unit discharge.

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13
Q

What are the twitch characteristics of fast twitch fibers?

A

High force, fast fatigue.

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14
Q

What is the effect of prolonged aerobic training on fast-twitch fibers?

A

They can become more fatigue-resistant, resembling slow-twitch fibers.

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15
Q

What factors influence muscle fiber type distribution in athletes?

A

Genetics and training.

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16
Q

How do gender differences affect muscle fiber composition?

A

Men generally have larger muscle fiber cross-sectional areas, while women tend to have more oxidative fibers.

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17
Q

What is the typical fiber type distribution in elite endurance athletes?

A

Predominantly slow-twitch fibers.

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18
Q

What occurs when a muscle cell can no longer produce ATP?

A

Muscles cannot contract, leading to fatigue.

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19
Q

What is the role of calcium in muscle contraction?

A

Calcium binds to troponin, allowing actin and myosin interaction.

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20
Q

What is the fiber-to-neuron ratio in motor units?

A

It varies; low ratio for intricate movements and high ratio for gross movements.

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21
Q

What is the primary function of motor units?

A

To facilitate muscle contraction through motor neuron innervation.

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22
Q

Why do muscles grow?

A

Muscles grow due to developmental processes and the overload principle, where adult skeletal muscle responds to mechanical stress, leading to adaptations.

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23
Q

What is the overload principle?

A

The overload principle states that adult skeletal muscle adapts to the mechanical stress placed upon it, known as the SAID principle (Specific Adaptation to Imposed Demands).

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24
Q

What is the stimulus for muscle growth?

A

Mechanical load induces muscle growth through processes like hypertrophy and changes in cross-sectional area (CSA).

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25
What is a key stimulus for muscle growth?
Resistance training (RT) is a key stimulus for muscle growth.
26
What are extreme models of muscle growth evidence?
Extreme models include hindlimb suspension, synergistic ablation, limb locking, tail weighted ladder climbs, and resistance wheels.
27
What is hypertrophy?
Hypertrophy is the increase in muscle mass and CSA, primarily through myofiber enlargement.
28
How does muscle quality correlate with CSA?
Increased CSA correlates with greater strength, and muscle quality is measured by mass normalized to force.
29
What is Cross-Sectional Area (CSA)?
CSA correlates with muscle tension development and can be anatomical (perpendicular to muscle's longitudinal axis) or physiological (perpendicular to fibers).
30
What is the difference between anatomical CSA and physiological CSA?
Anatomical CSA is measured perpendicular to the muscle's longitudinal axis, while physiological CSA is measured perpendicular to the fibers.
31
What is the relationship between length and CSA in muscle growth?
Length increases during development or extreme loading, while CSA typically increases 5-30% with resistance training without length increase.
32
What is fascicle growth?
Fascicle growth includes short-term edema-induced hypertrophy and long-term increases in CSA due to myofibrillar protein content.
33
What is myofiber hypertrophy?
Myofiber hypertrophy is the increase in individual fiber size through an increase in contractile proteins like actin and myosin.
34
What is the difference between hypertrophy and hyperplasia?
Hypertrophy is an increase in myofiber size, while hyperplasia is an increase in fiber number, which is more common during development.
35
What is sarcomere addition?
Muscle length increases through the addition of sarcomeres in series, which can be added at the ends or middle of myofibers.
36
What are the types of hypertrophy?
Sarcoplasmic hypertrophy increases non-contractile elements, while myofibrillar hypertrophy increases contractile proteins, leading to functional strength.
37
What are anabolic stimuli for muscle growth?
Anabolic stimuli include resistance training, protein intake, mechanical stress, mTOR signaling, and IGF-1.
38
What is myostatin?
Myostatin is a negative regulator that inhibits muscle growth and is a focus of research for potential therapies to enhance muscle growth.
39
What is the balance of protein synthesis and degradation?
Muscle size is a balance between protein synthesis (anabolic) and protein degradation (catabolic).
40
What happens during the fed state regarding protein synthesis?
Protein synthesis is elevated during the fed state.
41
What occurs post-exercise regarding protein synthesis?
There is a shift toward increased protein synthesis following resistance exercise.
42
What are key signals for load-induced muscle growth?
Key signals include mechanical stress, growth factors like IGF1, and mTOR activation.
43
What role does leucine play in muscle protein synthesis?
Leucine activates mTOR, promoting muscle protein synthesis.
44
What is the role of satellite cells in muscle growth?
Satellite cells are crucial for muscle repair and hypertrophy, especially after injury or intense exercise.
45
What happens without satellite cell activation?
Without activation, muscle tissue can become fibrotic and less responsive.
46
What is the effect of myostatin inhibition on muscle size?
Inhibition of myostatin leads to increased muscle size by blocking protein synthesis and promoting degradation.
47
What is the most common way for adult skeletal muscle to increase mass?
Hypertrophy primarily occurs through an increase in the size of individual muscle fibers.
48
What is the effect of adding sarcomeres in series?
Adding sarcomeres in series lengthens the muscle, increasing its range of motion and changing force generation properties.
49
What is the key protein for post-exercise hypertrophy?
Leucine is critical for activating mTOR and initiating protein synthesis for hypertrophy.
50
What is a negative regulator of muscle growth?
Myostatin (MSTN) inhibits muscle size, with low levels leading to excessive growth and high levels limiting hypertrophy.
51
What percentage of body mass is made up of skeletal muscle?
~40% of body mass is made up of skeletal muscle.
52
What are the primary functions of skeletal muscle?
Functions include posture, breathing, voluntary motion, and metabolic regulation.
53
What is sarcopenia?
Sarcopenia is the age-related loss of muscle strength and mass.
54
What are satellite cells?
Satellite cells are muscle stem cells located under the basal lamina.
55
What is the role of satellite cells in muscle adaptation?
They are essential for muscle repair and adaptation.
56
What are Type I muscle fibers?
Type I fibers are slow-twitch, oxidative, and fatigue-resistant.
57
What are Type II muscle fibers?
Type II fibers are fast-twitch, glycolytic, and fatigable.
58
What is the size principle of motor unit recruitment?
Motor units are recruited from smallest to largest depending on the force demand.
59
What is excitation-contraction coupling?
It links electrical signals to contraction.
60
What role does calcium play in excitation-contraction coupling?
Calcium binds to troponin, allowing actin-myosin crossbridge formation.
61
What is the all-or-none principle in motor units?
If a stimulus reaches threshold, all fibers in the motor unit contract fully.
62
What mechanisms adjust muscle force?
Force is adjusted via motor unit recruitment and firing frequency (rate coding).
63
How does fiber type distribution relate to athletic performance?
Endurance athletes have more Type I fibers; strength/power athletes have more Type II fibers.
64
What is the overload principle?
Mechanical stress from resistance training stimulates hypertrophy.
65
What is the difference between hypertrophy and hyperplasia?
Hypertrophy is growth via increased fiber size; hyperplasia is growth via fiber number increase.
66
What is sarcomere addition?
Sarcomeres can be added in series (length) or in parallel (width) depending on stimulus.
67
What is myofibrillar hypertrophy?
Myofibrillar hypertrophy involves more contractile proteins, leading to strength gains.
68
What is sarcoplasmic hypertrophy?
Sarcoplasmic hypertrophy involves more non-contractile components, resulting in size without strength.
69
How is muscle mass regulated?
Muscle mass is determined by the balance between anabolic (synthesis) and catabolic (degradation) processes.
70
What are the key anabolic signals for muscle growth?
Resistance training, mechanical tension, IGF-1, mTOR activation, and leucine.
71
What is the role of myostatin in muscle growth?
Myostatin is a negative regulator that suppresses muscle growth.
72
How do satellite cells contribute to hypertrophy and regeneration?
Satellite cells activate after damage or overload, contributing to muscle growth and repair.
73
What architectural changes can increase muscle size?
Adding sarcomeres in parallel increases cross-sectional area; in series increases muscle length.
74
What is muscle quality and how is it measured?
Muscle quality is the force produced per unit of muscle mass; measured as mass normalized to force output.
75
What are the two major types of hypertrophy?
Myofibrillar hypertrophy (more contractile proteins) and sarcoplasmic hypertrophy (more non-contractile fluid and components).
76
What is the Specific Adaptation to Imposed Demands (SAID) principle?
The SAID principle states that skeletal muscle will adapt specifically to the type of mechanical stress placed on it.
77
How does muscle protein synthesis change post-exercise?
Protein synthesis increases, especially when combined with nutrient intake, favoring hypertrophy.
78
How does muscle respond to mechanical load in terms of satellite cell behavior?
Mechanical load stimulates satellite cell activation, proliferation, and fusion to myofibers to support repair and growth.
79
What happens when myostatin is inhibited?
Muscle growth is enhanced, as myostatin normally limits protein synthesis and muscle size.
80
What structural adaptation allows a muscle to increase its functional range of motion?
Adding sarcomeres in series allows a muscle to lengthen and shift its force-length relationship.

MVS 340 FINAL (6 decks)

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