Question 1

Which dietary supplement is most likely to contribute to greater skeletal muscle ATP availability in the first few seconds of skeletal muscle contraction?

Accepted Answer

A)   fatty acids
B)   sports drinks with electrolytes and mineral spirits
C)   sugar
D)   protein
E)   creatine

Question 2

Which best describes "rigor mortis"?

Accepted Answer

A)   Lack of ATP following death causes cross-bridges to remain tightly bound to actin.
B)   Lack of ATP following death causes calcium to remain in the cytosol, continuously stimulating cross-bridge cycling.
C)   Repeated, high-frequency action potentials to a skeletal muscle fiber causes sustained contraction following death.
D)   Following death, calcium-activated proteases degrade all proteins in skeletal muscle fibers, making muscles limp.
E)   Build-up of K+ in T-tubules causes constant, tetanic contractions of skeletal muscles that last for about 12 hours following death.

Question 3

The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is called disuse atrophy.

Accepted Answer

A) True 
 B)False

Question 4

In skeletal muscle cells, calcium initiates contraction by binding to:

Accepted Answer

A)   tropomyosin.
B)   actin.
C)   troponin.
D)   myosin.
E)   the thick filament.

Question 5

Which of the following statements regarding myosin in skeletal muscle is TRUE?

Accepted Answer

A)   Myosin cross-bridge heads contain two binding sites, one for actin and one for tropomyosin.
B)   Myosin is an ATPase.
C)   The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle.
D)   All of the myosin cross-bridge heads in a thick filament are oriented and rotate in the same direction.
E)   Troponin covers the binding site on myosin molecules until Ca2+ binds to troponin to remove it from its blocking position.

Question 6

Myasthenia gravis is a collection of muscle disorders that cause muscle fatigue and weakness. What is the major mechanism?

Accepted Answer

A)   overproduction of acetylcholinesterase
B)   autoimmune destruction of nicotinic acetylcholine receptors
C)   demyelination of axons in motor pathways
D)   autoimmune destruction of L-type Ca2+ channels.
E)   a tumor that overproduces acetylcholine

Question 7

In cardiac muscle cells the release of Ca2+ through L-type Ca2+ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca2+ necessary for excitation-contraction coupling.

Accepted Answer

A) True 
 B)False

Question 8

In smooth muscle cells that can produce action potentials, cell membrane depolarization usually opens voltage-sensitive sodium channels.

Accepted Answer

A) True 
 B)False

Question 9

The difference in color between white muscle and red muscle is accounted for by the greater abundance of glycogen in white muscle.

Accepted Answer

A) True 
 B)False

Question 10

Which of the following is NOT a determinant of whole-muscle tension?

Accepted Answer

A)   the number of muscle fibers contracting
B)   the tension produced by each contracting fiber
C)   the numbers of motor units recruited
D)   the frequency of motor neuron stimulation
E)   the proportion of the muscle fibers within each motor unit that are contracting at any given time

Question 11

The term "twitch" refers to the mechanical response of a muscle fiber during one cross-bridge cycle.

Accepted Answer

A) True 
 B)False

Question 12

When a muscle has been repeatedly contracting at a moderate intensity for an extended period of time (more than a few minutes) , what is the primary source of ATP?

Accepted Answer

A)   transfer of energy and phosphate from creatine phosphate to ADP
B)   glycolysis
C)   oxidative phosphorylation
D)   breakdown of myosin
E)   uptake of ATP from the blood plasma

Question 13

A skeletal muscle generates its greatest twitch tension when it is stretched to twice its resting length.

Accepted Answer

A) True 
 B)False

Question 14

The larger the diameter of a skeletal muscle fiber, the greater the tension it can generate.

Accepted Answer

A) True 
 B)False

Question 15

When the load on a skeletal muscle is less than the tension the muscle generates, a concentric isotonic contraction results.

Accepted Answer

A) True 
 B)False

Question 16

Which type of skeletal muscle fiber typically has a smaller diameter?

Accepted Answer

A)   Type I
B)   Type II

Question 17

"Excitation-contraction coupling" refers to the binding of energized myosin to actin.

Accepted Answer

A) True 
 B)False

Question 18

Which of these would increase the tension generated in a skeletal muscle?

Accepted Answer

A)   increasing the frequency of firing in alpha motor neurons innervating the muscle
B)   stretching the muscle to very long lengths
C)   resting the muscle for several weeks
D)   switching off fast-glycolytic motor units and activating an equal number of slow-oxidative motor units
E)   increasing the amplitude of action potentials in the alpha motor neurons that innervate the muscle

Question 19

During concentric isotonic contraction of a skeletal muscle fiber, which of these occurs?

Accepted Answer

A)   sarcomeres lengthen
B)   A bands shorten
C)   I bands shorten
D)   A bands lengthen
E)   thin filaments shorten

Question 20

An action potential in the motor end plate rapidly spreads to the interior regions of a muscle cell by means of the:

Accepted Answer

A)   Z lines.
B)   sarcoplasmic reticulum.
C)   H zone.
D)   transverse tubules.
E)   pores in the plasma membrane.

Exam 9: Muscle

An action potential in the motor end plate rapidly spreads to the interior regions of a muscle cell by means of the:

Correct AnswerverifiedShow Answer

The difference in color between white muscle and red muscle is accounted for by the greater abundance of glycogen in white muscle.

Correct AnswerverifiedShow Answer

The larger the diameter of a skeletal muscle fiber, the greater the tension it can generate.

Correct AnswerverifiedShow Answer

Which type of skeletal muscle fiber typically has a smaller diameter?

Correct AnswerverifiedShow Answer

When the load on a skeletal muscle is less than the tension the muscle generates, a concentric isotonic contraction results.

Correct AnswerverifiedShow Answer

The decrease in mass and strength of muscle as a result of damage to the nerves innervating the muscle is called disuse atrophy.

Correct AnswerverifiedShow Answer

Which of the following is NOT a determinant of whole-muscle tension?

Correct AnswerverifiedShow Answer

In smooth muscle cells that can produce action potentials, cell membrane depolarization usually opens voltage-sensitive sodium channels.

Correct AnswerverifiedShow Answer

Which best describes "rigor mortis"?

Correct AnswerverifiedShow Answer

Which dietary supplement is most likely to contribute to greater skeletal muscle ATP availability in the first few seconds of skeletal muscle contraction?

Correct AnswerverifiedShow Answer

In skeletal muscle cells, calcium initiates contraction by binding to:

Correct AnswerverifiedShow Answer

Myasthenia gravis is a collection of muscle disorders that cause muscle fatigue and weakness. What is the major mechanism?

Correct AnswerverifiedShow Answer

"Excitation-contraction coupling" refers to the binding of energized myosin to actin.

Correct AnswerverifiedShow Answer

During concentric isotonic contraction of a skeletal muscle fiber, which of these occurs?

Correct AnswerverifiedShow Answer

Which of these would increase the tension generated in a skeletal muscle?

Correct AnswerverifiedShow Answer

The term "twitch" refers to the mechanical response of a muscle fiber during one cross-bridge cycle.

Correct AnswerverifiedShow Answer

A skeletal muscle generates its greatest twitch tension when it is stretched to twice its resting length.

Correct AnswerverifiedShow Answer

In cardiac muscle cells the release of Ca2+ through L-type Ca2+ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca2+ necessary for excitation-contraction coupling.

Correct AnswerverifiedShow Answer

When a muscle has been repeatedly contracting at a moderate intensity for an extended period of time (more than a few minutes) , what is the primary source of ATP?

Correct AnswerverifiedShow Answer

Which of the following statements regarding myosin in skeletal muscle is TRUE?

Correct AnswerverifiedShow Answer

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In cardiac muscle cells the release of Ca²⁺ through L-type Ca²⁺ channels depolarizes the sarcoplasmic reticulum and inhibits the release of any additional Ca²⁺ necessary for excitation-contraction coupling.

Correct Answer
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