Chapter 10

Every skeletal muscle fiber is supplied by a motor neuron at the NMJ. Watch this video (http://o (uscfiber) to leam more about what happens at the neuromuscular junction. (a) What is the definition of a motor unit? (b) What is the structural and functional difference between a large motor unit and a small motor unit? Can you give an example of each? (c) Why is the neurotransmitter acetylcholine degraded after binding to its receptor?

Muscle that has a striped appearance is described as being a. elastic b. nonstriated c. excitable d. striated

Which element is important in directly triggering contraction? a. sodium (Na \(^{+}\) ) b. calcium (Ca \(^{+t}\) ) c. potassium (K \(^{+}\) ) d. chloride (Cl)

Which of the following properties is not common to all three muscle tissues? a. excitability b. the need for ATP C. at rest, uses shielding proteins to cover actinbinding sites d. elasticity

The correct order for the smallest to the largest unit of organization in muscle tissue is a. fascicle, filament, muscle fiber, myofibril b. filament, myofibril, muscle fiber, fascicle c. muscle fiber, fascicle, filament, myofibril d. myofibril, muscle fiber, filament, fascicle

Depolarization of the sarcolemma means a. the inside of the membrane has become less negative as sodium ions accumulate b. the outside of the membrane has become less negative as sodium ions accumulate c. the inside of the membrane has become more negative as sodium ions accumulate d. the sarcolemma has completely lost any electrical charge

In relaxed muscle, the myosin-binding site on actin is blocked by a. titin b. troponin c. myoglobin d. tropomyosin

According to the sliding filament model, binding sites on actin open when a. creatine phosphate levels rise b. ATP levels rise c. acetylcholine levels rise d. calcium ion levels rise

The cell membrane of a muscle fiber is called a. myofibril b. sarcolemma c. sarcoplasm d. myofilament

Muscle relaxation occurs when a. calcium ions are actively transported out of the sarcoplasmic reticulum b. calcium ions diffuse out of the sarcoplasmic reticulum c. calcium ions are actively transported into the sarcoplasmic reticulum d. calcium ions diffuse into the sarcoplasmic reticulum

During muscle contraction, the cross-bridge detaches when a. the myosin head binds to an ADP molecule b. the myosin head binds to an ATP molecule c. calcium ions bind to troponin d. calcium ions bind to actin

Thin and thick filaments are organized into functional units called a. myofibrils b. myofilaments c. T-tubules d. sarcomeres

During which phase of a twitch in a muscle fiber is tension the greatest? a. resting phase b. repolarization phase C. contraction phase d. relaxation phase

Muscle fatigue is caused by a. buildup of ATP and lactic acid levels b. exhaustion of energy reserves and buildup of lactic acid levels c. buildup of ATP and pyruvic acid levels d. exhaustion of energy reserves and buildup of pyruvic acid levels

A sprinter would experience muscle fatigue sooner than a marathon runner due to a. anaerobic metabolism in the muscles of the sprinter b. anaerobic metabolism in the muscles of the marathon runner c. aerobic metabolism in the muscles of the sprinter d. glycolysis in the muscles of the marathon runner

What aspect of creatine phosphate allows it to supply energy to muscles? a. ATPase activity b. phosphate bonds c. carbon bonds d. hydrogen bonds

Drug \(X\) blocks ATP regeneration from \(A D P\) and phosphate. How will muscle cells respond to this drug? a. by absorbing ATP from the bloodstream b. by using ADP as an energy source c. by using glycogen as an energy source d. none of the above

The muscles of a professional sprinter are most likely to have a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers c. 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers

The muscles of a professional marathon runner are most likely to have a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers C. 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers d. 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers

Which of the following statements is true? a. Fast fibers have a small diameter. b. Fast fibers contain loosely packed myofibrils. c. Fast fibers have large glycogen reserves. d. Fast fibers have many mitochondria.

Which of the following statements is false? a. Slow fibers have a small network of capillaries. b. Slow fibers contain the pigment myoglobin. C. Slow fibers contain a large number of mitochondria. d. Slow fibers contract for extended periods.

Cardiac muscles differ from skeletal muscles in that they a. are striated b. utilize aerobic metabolism c. contain myofibrils d. contain intercalated discs

If cardiac muscle cells were prevented from undergoing aerobic metabolism, they ultimately would a. undergo glycolysis b. synthesize ATP C. stop contracting d. start contracting

Smooth muscles differ from skeletal and cardiac muscles in that they a. lack myofibrils b. are under voluntary control c. lack myosin d. lack actin

Which of the following statements describes smooth muscle cells? a. They are resistant to fatigue. b. They have a rapid onset of contractions. c. They cannot exhibit tetanus. d. They primarily use anaerobic metabolism.

From which embryonic cell type does muscle tissue develop? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells

Which cell type helps to repair injured muscle fibers? a. ganglion cells b. myotube cells c. myoblast cells d. satellite cells

Why is elasticity an important quality of muscle tissue?

What would happen to skeletal muscle if the epimysium were destroyed?

Describe how tendons facilitate body movement.

What are the opposite roles of voltage-gated sodium channels and voltage-gated potassium channels?

How would muscle contractions be affected if skeletal muscle fibers did not have T-tubules?

What causes the striated appearance of skeletal muscle tissue?

Why does a motor unit of the eye have few muscle fibers compared to a motor unit of the leg?

What factors contribute to the amount of tension produced in an individual muscle fiber?

Why do muscle cells use creatine phosphate instead of glycolysis to supply ATP for the first few seconds of muscle contraction?

Is aerobic respiration more or less efficient than glycolysis? Explain your answer.

What changes occur at the cellular level in response to endurance training?

What changes occur at the cellular level in response to resistance training?

What would be the drawback of cardiac contractions being the same duration as skeletal muscle contractions?

How are cardiac muscle cells similar to and different from skeletal muscle cells?

Describe the differences between single-unit smooth muscle and multiunit smooth muscle.

Why is muscle that has sustained significant damage unable to produce the same amount of power as it could before being damaged?

Which muscle type(s) (skeletal, smooth, or cardiac) can regenerate new muscle cells/fibers? Explain your answer.