Question 1

During muscle relaxation (following a muscle contraction),calcium is moved back into the sarcoplasmic reticulum via simple diffusion.

Accepted Answer

Calcium is actively transported back into the sarcoplasmic reticulum during muscle relaxation.

Question 2

One of the proposed mechanisms to explain the positive impact of postactivation potential on muscle performance is that low intensity muscle contractions results in phosphorylation of myosin light chains (i.e. ,proteins located at the base of the myosin cross-bridge).This increased phosphorylation can increase muscle force production by
A)increasing the muscle's sensitivity to calcium.
B)increasing the calcium release from the sarcoplasmic reticulum.
C)promoting increased ATP availability in the muscle.
D)none of the above answers are correct

Accepted Answer

Phosphorylation of myosin light chains increases the muscle's sensitivity to calcium, which can lead to an increase in force production. Option B (increasing calcium release from the sarcoplasmic reticulum) is not directly influenced by myosin light chain phosphorylation, and option C (increased ATP availability) is not a direct mechanism for postactivation potentiation.

Question 3

In contrast to power athletes,endurance athletes typically possess a low percentage of slow fibers and a high percentage of fast fibers.

Accepted Answer

Endurance athletes typically require a higher percentage of slow-twitch (Type I) muscle fibers for sustained aerobic activity, while power athletes rely on a higher percentage of fast-twitch (Type II) muscle fibers for explosive movements.

Question 4

Age-related loss of skeletal muscle mass is called sarcopenia.

Accepted Answer

Sarcopenia is a well-known age-related condition characterized by a loss of muscle mass and strength.

Question 5

Abundant evidence indicates that rigorous exercise training can result in a conversion of muscle fiber type.

Accepted Answer

Rigorous exercise training has been shown to result in a shift from Type IIx to Type IIa muscle fibers, which are more oxidative and better suited for endurance activities. This conversion is believed to be due to an increase in mitochondrial density and aerobic enzyme content within the muscle fibers.

Question 6

The force velocity curve describes the relationship between speed of muscle shortening (i.e. ,velocity of movement)and muscle force production.Which of the following statements are true about the influence of muscle fiber type on the force velocity curve?
A)At any given velocity of movement,the peak power generated is greater in a muscle that contains a high percentage of fast fibers (i.e. ,type IIx)compared with a muscle that contains a high percentage of slow fibers (i.e. ,type I).
B)At any given velocity of movement,the peak power generated is lower in a muscle that contains a high percentage of fast fibers (i.e. ,type IIx)compared with a muscle that contains a high percentage of slow fibers (i.e. ,type I).
C)At low movement speeds,the peak power generated is greater in a muscle that contains a high percentage of slow fibers (i.e. ,type I)compared with a muscle that contains a high percentage of fast fibers (i.e. ,type IIx).
D)None of the above answers are correct.

Accepted Answer

Muscle fibers can be categorized as slow-twitch (type I) and fast-twitch (type II) fibers, with type II further classified as type IIa and type IIx. Type IIx fibers have the fastest shortening velocity, but they fatigue quickly, while type I fibers have a slower shortening velocity but can sustain contractions for longer durations. Therefore, at any given velocity of movement, a muscle containing a higher percentage of type IIx fibers generates greater peak power than a muscle with a higher percentage of type I fibers. This is because type IIx fibers can produce greater force than type I fibers due to their larger cross-sectional area and higher myosin-ATPase activity.

Question 7

The peak power generated by any skeletal muscle increases with increasing velocities of movement up to a movement speed of 200-300 degrees per second.Which of the following factors can explain this observation?
A)ATPase activity decreases as a function of the speed of muscle shortening.
B)Myosin cross-bridges develop velocity-related fatigue.
C)muscle ATP levels are depleted at shortening velocities above 300 degrees per second.
D)None of the above answers are correct

Accepted Answer

The peak power generated by skeletal muscle increases with increasing velocities of movement up to a certain point due to the rate at which myosin cross-bridges can cycle and produce force. This is not directly due to ATPase activity decreasing, myosin cross-bridges developing velocity-related fatigue, or muscle ATP levels being depleted at high shortening velocities. Instead, it's related to the intrinsic properties of muscle contraction mechanics and the force-velocity relationship.

Question 8

A popular belief among many athletes and coaches is that exercise-induced muscle cramps in a single muscle (e.g. ,gastrocnemius)results from dehydration and blood electrolyte imbalance.Which of the following observations DO NOT support this position?
A)Dehydration and electrolyte imbalance affects the entire body.
B)Exercise-induced muscle cramps can occur without any change in blood electrolyte concentrations.
C)Static stretching of the cramping muscle often relieves the cramp.
D)all of the above answers are correct

Accepted Answer

All three observations do not support the belief that exercise-induced muscle cramps in a single muscle are solely caused by dehydration and blood electrolyte imbalance. Dehydration and electrolyte imbalance affect the entire body, not just a single muscle. Additionally, exercise-induced muscle cramps can occur without any changes in blood electrolyte concentrations, and static stretching of the cramping muscle often relieves the cramp, suggesting that muscle fatigue and neural control may play a role in the development of cramps.

Question 9

If you continue to increase the firing rate (of action potentials)of a motor neuron,then all of the skeletal muscle fibers it innervates will eventually summate to reach tetanus.

Accepted Answer

This is due to the process of temporal summation, where each subsequent action potential would cause a greater release of calcium ions in the muscle fibers, leading to stronger and more sustained contractions until tetanus is reached.

Question 10

High activity of the enzyme ATPase is found in both slow-twitch (type I)and fast-twitch (type IIx)fibers.

Accepted Answer

High activity of the enzyme ATPase is found in fast-twitch fibers (type II), especially type IIx, which are adapted for rapid, powerful movements and fatigue quickly. Slow-twitch fibers (type I) are more efficient at using oxygen to generate ATP for continuous, extended muscle contractions over a long time, and thus, have lower ATPase activity compared to type IIx fibers.

Quiz 9: Skeletal Muscle: Structure and Function

During muscle relaxation (following a muscle contraction),calcium is moved back into the sarcoplasmic reticulum via simple diffusion.

In contrast to power athletes,endurance athletes typically possess a low percentage of slow fibers and a high percentage of fast fibers.

Age-related loss of skeletal muscle mass is called sarcopenia.

Abundant evidence indicates that rigorous exercise training can result in a conversion of muscle fiber type.

The force velocity curve describes the relationship between speed of muscle shortening (i.e. ,velocity of movement) and muscle force production.Which of the following statements are true about the influence of muscle fiber type on the force velocity curve?

The peak power generated by any skeletal muscle increases with increasing velocities of movement up to a movement speed of 200-300 degrees per second.Which of the following factors can explain this observation?

A popular belief among many athletes and coaches is that exercise-induced muscle cramps in a single muscle (e.g. ,gastrocnemius) results from dehydration and blood electrolyte imbalance.Which of the following observations DO NOT support this position?

If you continue to increase the firing rate (of action potentials)of a motor neuron,then all of the skeletal muscle fibers it innervates will eventually summate to reach tetanus.

High activity of the enzyme ATPase is found in both slow-twitch (type I)and fast-twitch (type IIx)fibers.