Deck 6: Contraction of Skeletal Muscle

Question 1

During the contraction of a skeletal muscle fiber, the actin and myosin filaments slide past each other. Which of the following represents expected changes in the widths of I bands and A bands during the contraction process?

Answer 1

D

Question 2

A 28-year-old man has been training as a distance runner for the past 6 years. Compared with a sprinter, which of the following is most likely to be decreased in the skeletal muscles of this athlete during resting conditions?

A)Capillary density
B)Glycolytic enzyme content
C)Mitochondrial volume density
D)Myoglobin content
E)Oxidative capacity

Answer 2

A

Question 3

The skeletal muscle sarcomere normally has a narrow range of lengths in vivo, but sarcomere length can vary greatly in vitro under nonphysiological conditions. The diagram shows sarcomeres at various lengths. At which length can the sarcomere exert its maximum force during an isometric contraction?


A. $1.6 \mu \mathrm { m }$
B. $2.1 \mu \mathrm { m }$
C. $2.8 \mu \mathrm { m }$
D. $3.0 \mu \mathrm { m }$
E. $3.5 \mu \mathrm { m }$

Answer 3

B

Question 4

A 29-year-old woman has been training as a distance runner for the past 5 years. Which set of changes best describes the skeletal muscles of this woman compared with a sprinter? $$\begin{array} { l l l l } \underline{\text { Capillary Density }} & \underline{\text { Oxidative Capacity} } & \underline{\text { Myoglobin Content }} & \underline{\text { Fiber Diameter} } \\\text { A. Decreased } & \text { Decreased } & \text { Decreased } & \text { Decreased } \\\text { B. Decreased } & \text { Decreased } & \text { Increased } & \text { Increased } \\\text { C. Increased } & \text { Increased } & \text { Decreased } & \text { Decreased } \\\text { D. Increased } & \text { Increased } & \text { Increased } & \text { Decreased } \\\text { E. Increased } & \text { Increased } & \text { Increased } & \text { Increased }\end{array}$$

Question 5

The diagram shows force-velocity relationships for three different skeletal muscles. Which of the follopving curves most likely correspond to glycolytic, oxidative, and mixed muscle types?


$\begin{array}{c}\begin{array}{l} \underline{\text { Glycolytic}}\\A. \quad \mathrm{X} \\B.\quad \mathrm{X} \\C. \quad\mathrm{Y}\\D.\quad \mathrm{Y}\\E.\quad \mathrm{Z}\\F. \quad\mathrm{ Z } \end{array}\begin{array}{l} \underline{\text { Oxidative} } \\\mathrm{Y} \\\mathrm{Z} \\\mathrm{X} \\\mathrm{Z} \\\mathrm{X} \\\mathrm{Y}\end{array}\begin{array}{l}\text { Mixed } \\\hline \underline{ \mathrm{Z}} \\\mathrm{Y} \\\mathrm{Z} \\\mathrm{X} \\\mathrm{Y} \\\mathrm{X}\end{array} \end{array}$

Question 6

High-frequency stimulation of a skeletal muscle causes tetanic contraction because the intracellular concentration of which of the following substances increases and remains at high levels?

A)Adenosine triphosphate
B)Calcium
C)Potassium
D)Sodium
E)Troponin

Question 7

The diagram shows the relationship between contraction velocity and force. Which of the following muscles is most likely to correspond to muscle number 1 shown on the diagram (assume that all muscles shown are at their normal resting lengths).


A.

B.

C.

D.

E.

Question 8

When a person lifts a 25-pound weight, what type(s) of muscle contraction are involved?

A)Isometric contraction only
B)Isotonic contraction only
C)Isometric contraction followed by isotonic contraction
D)Isotonic contraction followed by isometric contraction

Question 9

The diagram shows the relationship between muscle tension and sarcomere length for muscle. Which point on the curve represents tension development at a normal resting length for skeletal muscle?

Question 10

The diagram shows the relationship between muscle tension and sarcomere length for muscle. Which point 'on the curve represents tension development at a normal resting length for skeletal muscle?

Question 11

A 24-year-old medical student goes to the local gym to lift weights. She begins by bench-pressing 100 pounds as a warm-up procedure and then gradually increases the weight. Which of the following occurs as she adds more weight?

A)Decreased frequency of motor nerve action potentials
B)Decreased velocity of motor nerve action potentials
C)Increased frequency of motor nerve action potentials
D)Increased velocity of motor nerve action potential
E)Involvement of fewer motor units

Question 12

The increase in muscle mass that typically occurs with weight training is most likely caused by an increase in the number of which of the following?

A)Capillaries
B)Mitochondria
C)Muscle fibers
D)Myofibrils

Question 13

The color of a type I skeletal muscle fiber can be attributed to a relative abundance of which of the following compared to type II muscle fiber?

A)Blood capillaries
B)Mitochondria
C)Myoglobin
D)Myosin adenosine triphosphatase
E)Oxidative enzymes

Question 14

The diagram shows the relationship between contraction velocity and force. Which of the following muscles is most likely to correspond to muscle number 2 shown on the diagram (assume that all muscles shown are at their normal resting lengths)?


A.

B.

C.

D.

Question 15

A 45-year-old man goes to the local gym to lift weights. He begins by bench-pressing 130 pounds as a warm-up procedure and then gradually increases the weight. Which of the following sets of changes occurs as he adds more weight?
$\begin{array} { l l l } & \underline{\text { Activation of Motor Units } }&\underline{ \text { Frequency of Motor Nerve Action Potentials} } \\ \text { A. } & \text { Decreased } & \text { Decreased } \\ \text { B. } & \text { Decreased } & \text { Increased } \\ \text { C. } & \text { Decreased } & \text { No change } \\ \text { D. } & \text { Increased } & \text { Decreased } \\ \text { E. } & \text { Increased } & \text { Increased } \\ \text { F. } & \text { Increased } & \text { No change } \end{array}$

Question 16

The dark color of red skeletal muscle (slow twitch muscle) can be attributed to a relative abundance of which of the following compared with white skeletal muscle (fast twitch muscle)?

A)Blood capillaries
B)Mitochondria
C)Myoglobin
D)Myosin adenosine triphosphatase
E)Oxidative enzymes

Question 17

A 24-year-old woman is admitted to the emergency department after an automobile accident in which lacerations to the left wrist severed a major tendon. The severed ends of the tendon were overlapped by 6 cm to facilitate suturing and reattachment. Which of the following characteristics would be expected after 6 weeks compared with the preinjured muscle? Assume that series growth of sarcomeres cannot be completed within 6 weeks. $\quad$$\underline{\text {Passive Tension}}$ $\quad$ $\underline{\text {Maximal Active Tension}}$
A. $\text {Decrease }$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text {Decrease}$
B. $\text { Decrease}$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Increase}$
C. $\text { Increase}$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Increase}$
D. $\text { Increase}$$\quad$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { Decrease}$
E. $\text {No change}$$\quad$$\quad$$\quad$$\quad$$\quad$$\text { No change}$

Question 18

The length-tension diagram shown was obtained from a skeletal muscle with equal numbers of red and white fibers. Supramaximal tetanic stimuli were used to initiate an isometric contraction at each muscle length studied. The resting length was 20 $\mathrm { cm }$ . What is the maximum amount of active tension this muscle is capable of generating at a preload of 100 grams?

A. 145 to 155 grams
B. 25 to 35 grams
C. 55 to 65 grams
D. 95 to 105 grams
E. Cannot be determined

Question 19

The length-tension diagram shown was obtained from a skeletal muscle with equal numbers of red and white fibers. Supramaximal tetanic stimuli were used to initiate an isometric contraction at each muscle length studied. What are the values (in grams) of preload, active tension, and total tension when the muscle length is $60 \mathrm {~cm}$ ?


$\begin{array} { l ccc } &\underline{ \text { Preload }} & \underline{\text { Active Tension }} &\underline{ \text { Total Tension }} \\ \text { A. } & 100 & 200 & 300 \\ \text { B. } & 100 & 300 & 200 \\ \text { C. } & 150 & 250 & 300 \\ \text { D. } & 200 & 100 & 300 \\ \text { E. } & 200 & 200 & 300 \end{array}$

Question 20

A physiology experiment is conducted in which a skeletal muscle twitch is initiated with an electrical stimulator. Which factor contributes to the termination of a typical skeletal muscle twitch?

A)Calcium uptake by sarcoplasmic reticulum
B)Closure of transverse tubules
C)Depletion of calcium stores from sarcoplasmic reticulum
D)Exhaustion of muscle adenosine triphosphate stores
E)Stimulation of dihydropyridine (DHP) receptors

Question 21

The relatively high maximum velocity of shortening of a skeletal muscle containing predominately type II fibers can be partially attributed to a relative abundance of which of the following substances, compared to a muscle containing predominately type I fibers?

A)Blood capillaries
B)Mitochondria
C)Myoglobin
D)Myosin adenosine triphosphatase
E)Oxidative enzymes

Question 22

A nerve that normally innervates a predominately type I muscle is anastomosed (connected) to a predominately type II muscle. Which of the following is most likely to increase in the predominately type II muscle after transinnervation surgery?

A)Glycolytic capacity
B)Fiber diameter
C)Mitochondrial content
D)Maximum velocity of contraction