Chapter 06

Hall: Guyton and Hall Textbook of Medical Physiology, 12th Edition Chapter 06: Contraction of Skeletal Muscle Test Bank 1.

A 28-year-old man has been training as a distance runner for the past six years. Compared with a sprinter, which of the following is 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

ANS: A 2. A physiology experiment is conducted in which a skeletal muscle twitch is initiated using 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 ATP stores E. Stimulation of dihydropyridine (DHP) receptors ANS: A 3. A 24-year-old medical student goes to the local gym to lift weights. She begins by benchpressing 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 ANS: C 4. 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 six weeks compared with the preinjured muscle? Assume that series growth of sarcomeres cannot be completed within six weeks. Passive tension A. Decrease

Maximal active tension Decrease

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.

200 Test Bank B. C. D. E.

Decrease Increase Increase No change

6-2

No

Increase Increase Decrease change

ANS: D 5. During the contraction of a skeletal muscle fiber, the actin and myosin filaments slide past each other. Which of the following represent expected changes in the widths of I-bands and A-bands during the contraction process? I-band width A-band width A. ↑ ↔ B. ↓ ↑ C. ↓ ↓ D. ↓ ↔ 150 ↑ E. ↔ ANS: D 6. When a person lifts a 25-pound involved? A. Isometric contraction only B. Isotonic contraction only C. Isometric contraction D. Isotonic contraction

weight, what type or types of muscle contraction are

followed by isotonic contraction followed by isometric contraction

ANS: C 7. The length-tension diagram shown was obtained from a skeletal muscle with equal numbers of red and white fibers. Supramaximal tetanic Tension stimuli were used to initiate an (grams) isometric contraction at each 100 muscle length studied. The resting length was 20 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 to105 grams E. Cannot be determined

0

10

20 30 Length (cm)

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.

40

50 Test Bank

6-3

ANS: C 8. 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? C ANS: C

B

Tension

D A

E Length

0 9. The diagram shows the relationship between muscle tension and sarcomere length for muscle. Which point on the curve represents tension development C at a normal resting length for cardiac muscle? ANS: B

B Tension D

A

E Length

10. A 29-year-old woman has been training as a distance runner for the past five years. Which set of changes best describes the skeletal muscles of this woman compared with a sprinter? Capillary density Oxidative capacity Myoglobin content Fiber diameter

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.

400 Test Bank A. B. C. D. E.

6-4 Decreased Decreased Decreased Increased Increased Decreased Increased Decreased Increased Increased

Decreased

Decreased

Decreased

Increased

Increased

Decreased

Increased

Increased

Increased

Increased

ANS: D 11. The length-tension diagram shown on the right was obtained 300 from a skeletal muscle with equal numbers of red and white Tension fibers. Supramaximal tetanic stimuli were used to initiate an (grams) 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 cm? Preload Active tension Total tension A. 100 200 B. 100 300 C. 150 250 D. 200 100 E. 200 200

0

20

40 60 Length (cm)

300 200 300 300 300 200

ANS: A 12. A 45-year-old man goes to the pressing 130 pounds as a warmweight. Which of the following Activation of motor potentials A. Decreased B. Decreased C. Decreased D. Increased

local gym to lift weights. He begins by benchup procedure and then gradually increases the sets of changes occur as he adds more weight? units Frequency of motor nerve action Decreased Increased No change Decreased

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.

80

100 Test Bank E. F.

6-5 Increased Increased

Increased No change

ANS: E

13.

The skeletal muscle sarcomere normally has a narrow range of lengths in vivo, but sarcomere length can vary greatly in vitro under non0 shows physiological conditions. The diagram sarcomeres at various lengths. At which length can the sarcomere exert its maximum force during an isometric contraction? A. 1.6 µm B. 2.1 µm C. 2.8 µm D. 3.0 µm E. 3.5 µm

ANS: B

14.

1.6 2.02.3 µm µmµm

3.7 µm

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 1 all muscles shown are at their normal resting lengths). Contraction velocity A. 4 5 B. 3 0

0

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.

Force

2

Test Bank

6-6

C. D. E. ANS: E

15.

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 Contraction that all muscles shown are at their normal resting velocity lengths)?

1

4

A. B. C.

5

3 0

2

0

Force

D. E. ANS: D 16.

The diagram shows force-velocity relationships for three different skeletal muscles. Which of the following curves most likely correspond to glycolytic, oxidative, and mixed muscle types? Contraction Glycolytic Oxidative Mixed velocity A. X Y Z B. X Z Y C. Y X Z D. Y Z X E. Z X Y F. Z Y X

ANS: B

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X Y Z 0

0

Force

Test Bank 17.

6-7

The dark color of red skeletal muscle (slow twitch muscle) can be attributed to a relative abundance of which of the following compared to white skeletal muscle (fast twitch muscle)? A. Blood capillaries B. Mitochondria C. Myoglobin D. Myosin ATPase E. Oxidative enzymes

ANS: C

Copyright © 2011, 2006 by Saunders, an imprint of Elsevier Inc.