Deck 9: Skeletal Muscle: Structure and Function

Question 1

A muscular contraction that results in a movement of body parts is called a(n)

A)isometric contraction.
B)static contraction.
C)isotonic or dynamic contraction.
D)muscle twitch.

Answer 1

C

Question 2

The specific tension (i.e. ,force production per cross sectional area of the fiber)differs between fiber types.Which of the following answers is correct in regard to specific force production?

A)type I is greater than type IIa and IIx
B)type IIx is greater than type I and IIa
C)type IIx is greater than type I
D)type IIa is greater than type IIx

Answer 2

C

Question 3

Calcium is stored in muscle within the

A)Golgi organs.
B)H zone.
C)sarcoplasmic reticulum.
D)sarcolemma.

Answer 3

C

Question 4

The connecting point between a motor neuron and muscle cell is called the

A)end-plate potential.
B)motor unit.
C)sarcolemma.
D)neuromuscular junction.

Question 5

Skeletal muscle fibers that contain moderate-to-high numbers of mitochondria could be classified as

A)type I fibers
B)type IIa fibers
C)either type I or type IIa
D)type IIx

Question 6

The formation of cross-bridges that initiates the contractile process in skeletal muscle is triggered by

A)calcium binding to myosin.
B)calcium binding to tropomyosin.
C)calcium binding to troponin.
D)ATP binding to the myosin cross-bridges.

Question 7

The cell membrane around a muscle fiber is called the

A)soma.
B)plasma membrane.
C)mucous membrane.
D)sarcolemma.

Question 8

The amount of force exerted during muscular contraction is dependent on the

A)type of motor units recruited ONLY.
B)type of motor units recruited,the initial length of the muscle,and the nature of the neural stimulation.
C)length of the muscle fibers ONLY.
D)nature of the neural stimulation ONLY.

Question 9

Fast-twitch fibers (i.e. ,type IIx)contain a relatively

A)large number of mitochondria and low ATPase activity.
B)small number of mitochondria and low ATPase activity.
C)small number of mitochondria and high ATPase activity.
D)moderate numbers of mitochondria and low ATPase activity

Question 10

Postactivation potentiation is defined as

A)the increase in muscle force production that occurs following consumption of a high carbohydrate meal.
B)the increase in muscle force production that occurs following a bout of non-fatiguing,submaximal contractions.
C)the increase in muscle force production that occurs following a bout of fatiguing,maximal contractions.
D)none of the above answers are correct

Question 11

Disease-related muscle wasting is referred to as

A)cachexia.
B)proteolysis.
C)myobiogenesis.
D)None of the above answers are correct

Question 12

Which of the following has been shown to cause muscle fatigue?

A)the accumulation H⁺
B)the accumulation of ATP
C)the accumulation of inorganic phosphate
D)both A and C are correct

Question 13

The two principal contractile proteins found in skeletal muscle are

A)actin and troponin.
B)actin and myosin.
C)troponin and tropomyosin.
D)myosin and tropomyosin.

Question 14

Which of the following events occurs first during a voluntary muscle contraction?

A)The T-tubules depolarize,causing calcium to be released from the sarcoplasmic reticulum.
B)Calcium is resequestered (taken up)into the sarcoplasmic reticulum.
C)Tropomyosin moves,exposing the actin active sites.
D)The innervating alpha-motor neuron reaches an action potential.

Question 15

The breakdown of ATP in muscle is accomplished via the enzyme

A)lactate dehydrogenase.
B)succinate dehydrogenase.
C)ATPase.
D)phosphofructokinase.

Question 16

A highly successful endurance athlete would likely have ________________ compared to a sedentary person.

A)a higher percentage of type IIB fibers
B)a higher percentage of type I fibers
C)a higher percentage of type IIx fibers
D)an equal percentage of type I and type IIx fibers

Question 17

Satellite cells

A)contribute to muscle growth by dividing and contributing nuclei to existing muscle fibers.
B)reside above the sarcolemma.
C)are undifferentiated cells that play a key role in muscle growth and repair.
D)all of the above answers are correct

Question 18

The layer of connective tissue that surrounds the outside of skeletal muscle (i.e. ,just below the fascia)is called the

A)epimysium.
B)perimysium.
C)endomysium.
D)basement membrane.

Question 19

Which type of muscle fiber has been shown to be the most efficient?

A)type I.
B)type IIa.
C)type IIx.
D)type I and type IIx have equal efficiency.

Question 20

The motor neuron and all the muscle fibers it innervates is called a ______.

A)motor junction.
B)motor unit.
C)motor end plate.
D)motor nerve.

Question 21

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

Question 22

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

Question 23

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

Question 24

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

Question 25

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

Question 26

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.

Question 27

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

Question 28

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

Question 29

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.

Question 30

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