1. 6
The Muscular System 1

2. 1. Which muscle type(s) are under voluntary control?
Skeletal
Smooth
Cardiac
All of the above
A. Skeletal

3. 1. Which muscle type(s) are under voluntary control?
Answer:
a. Skeletal
Explanation:
Skeletal muscle is the only muscle type that is voluntary.

4. 2. What are muscle groups that work together for a common action or movement called?
Antagonistic
Origins
Insertions
Synergistic
D. synergistic

5. 2. What are muscle groups that work together for a common action or movement called?
Answer:
d. Synergistic
Explanation:
Skeletal muscles often occur in groups that work together to perform the same action, termed “synergistic” muscles. Antagonistic muscles act in opposition. Origin and insertion describe muscle attachment to the bone.

6. 3. What is the structural and contractile unit of a skeletal muscle called?
Myofilament
Myofibril
Sarcoplasmic reticulum
Sarcomere
D. sarcomere

7. 3. What is the structural and contractile unit of a skeletal muscle called?
Answer:
d. Sarcomere
Explanation:
Myofilaments are parts of a sarcomere; myofibrils contain sarcomeres; and the sarcoplasmic reticulum is a separate organelle.

8. 4. What is the specialized organelle that stores calcium in a skeletal muscle cell called?
Golgi complex
Rough ER
Sarcomere
Sarcoplasmic reticulum
D. Sarcoplasmic reticulum

9. 4. What is the specialized organelle that stores calcium in a skeletal muscle cell called?
Answer:
d. Sarcoplasmic reticulum
Explanation:
The sarcoplasmic reticulum stores calcium and is a specialized type of smooth endoplasmic reticulum. Golgi complex and Rough ER are organelles involved with other functions while the Sarcomere is the structural and contractile unit of a skeletal muscle.

10. 5. Which of the following are types of myofilaments found in sarcomeres?
Myosin and actin
Sarcoplasmic reticulum and calcium
ATP and calcium
Smooth ER and sarcoplasmic reticulum
A. Myosin and actin

11. 5. Which of the following are types of myofilaments found in sarcomeres?
Answer:
a. Myosin and actin
Explanation:
Thick filaments are made of myosin, while the thin filaments are made mostly of actin.

12. 6. Which of the following occur during the power stroke of muscle contraction?
Acetylcholine binds to receptors.
Myosin heads pull on actin filaments.
Calcium is pumped out of the sarcomere.
ATP is split by the myosin head into ADP and Pi.
B. Myosin heads pull on actin filaments.

13. 6. Which of the following occur during the power stroke of muscle contraction?
Answer:
b. Myosin heads pull on actin filaments.
Explanation:
According to the sliding filament model, myosin heads bind with actin and then move, pulling actin toward the midline of the sarcomere, thus shortening the sarcomere.

14. 7. Acetylcholine is secreted by which of the following structures?
Sarcoplasmic reticulum
Sarcomere
Motor neuron
Troponin-tropomyosin complex
C. Motor neuron

15. 7. Acetylcholine is secreted by which of the following structures?
Answer:
c. Motor neuron
Explanation:
When a nerve impulse arrives at the neuromuscular junction, the motor neuron releases acetylcholine. Acetylcholine diffuses across the synaptic cleft and binds to protein receptors in the plasma membrane of the muscle cell.

16. 8. What process is involved during rigor mortis?
The muscles’ proteins, actin and myosin, gradually break down, allowing the muscles to become stiff.
Without ATP, cross-bridges cannot be broken, and within 3 to 4 hours after death the muscles become stiff.
There is an excess of ATP and within 3 to 4 hours after death the muscles become stiff as they go into tetanus.
B. Without ATP, cross-bridges cannot be broken, and within 3 to 4 hours after death the muscles become stiff

17. 8. What process is involved during rigor mortis?
Answer:
b. Without ATP, cross-bridges cannot be broken, and within 3 to 4 hours after death the muscles become stiff.
Explanation:
After a person dies, ATP is no longer being produced; without ATP, cross-bridges cannot be broken, and within 3 to 4 hours after death the muscles become stiff. The muscles’ proteins gradually break down, allowing the muscles to relax again after 2 to 3 days.

18. 9. Which of the following is the most powerful?
Fast-twitch muscles
Mixed muscles
Slow-twitch muscles
Slow-twitch and fast-twitch muscles have the same strength.
A. Fast-twitch muscles

19. 9. Which of the following is the most powerful?
Answer:
a. Fast-twitch muscles
Explanation: Fast-twitch muscle cells are bigger in diameter and contract more rapidly and powerfully than slow-twitch cells. But fast-twitch muscle cells have far less endurance than slow-twitch cells.

20. 10. What is the name of the process used by the nervous system to increase the strength of muscle contraction by stimulating more motor units?
Summation
Tetanus
Oxygen debt
Recruitment
D. Recruitment

21. 10. What is the name of the process used by the nervous system to increase the strength of muscle contraction by stimulating more motor units?
Answer:
d. Recruitment
Explanation:
A motor unit is a motor neuron and all of the muscle cells that it stimulates. Recruiting more motor units results in the contraction of more muscle cells and thus a more powerful contraction.

22. 11. The primary source of ATP is a series of chemical reactions called _____, which use _____ and _____.
mitochondria; lactic acid; calcium
sarcomeres; myosin; actin
aerobic respiration; oxygen; glucose
aerobic respiration; calcium; acetylcholine
C. aerobic respiration; oxygen; glucose

23. 11. The primary source of ATP is a series of chemical reactions called _____, which use _____ and _____.
Answer:
c. aerobic respiration; oxygen; glucose
Explanation:
Aerobic respiration occurs in the mitochondria and uses oxygen and glucose to make ATP.