Question 1

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.F) B) and C)
G) A) and E)

Question 2

The force-generating sites in a myofibril are the Z lines.

Accepted Answer

A) True 
 B)False

Question 3

Actin is an ATPase enzyme.

Accepted Answer

A) True 
 B)False

Question 4

Which is a TRUE statement about excitation-contraction coupling?

Accepted Answer

A)  In skeletal muscle cells,it requires the influx of extracellular calcium ion.
B)  In smooth muscle cells,it must be preceded by an action potential in the cell membrane.
C)  In all kinds of muscle it requires the entry of calcium from the extracellular fluid.
D)  Calcium-induced calcium-release plays a role in cardiac muscle cells,as well as in some smooth muscle cells.
E)  In skeletal muscle cells,EC coupling begins when an action potential propagates along the sarcoplasmic reticulum membrane.F) B) and E)
G) B) and D)

Question 5

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 acetylcholineF) A) and D)
G) A) and B)

Question 6

Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular junctions,while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.

Accepted Answer

A) True 
 B)False

Question 7

During skeletal-muscle contraction,the distance between the Z lines of a sarcomere decreases because of shortening of the filaments.

Accepted Answer

A) True 
 B)False

Question 8

The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules.

Accepted Answer

A) True 
 B)False

Question 9

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 10

Fast-glycolytic muscle fibers differ from slow-oxidative fibers in that:

Accepted Answer

A)   fast-glycolytic fibers rely on creatine phosphate as an ATP source for the first few seconds of contraction butSlow-oxidative fibers do not.
B)   fast-glycolytic fibers have a smaller diameter than slow-oxidative fibers.
C)   fast-oxidative fibers can generate greater maximal tension than slow-oxidative fibers.
D)   fast-oxidative fibers generate less lactic acid than slow-oxidative fibers.E) B) and D)
F) None of the above

Question 11

The name given to the repeating functional units that cause striations in a skeletal muscle myofibril is "sarcomere."

Accepted Answer

A) True 
 B)False

Question 12

Which type of skeletal muscle fibers is generally recruited first?

Accepted Answer

A)  Type I
B)  Type IIC) A) and B)
D) undefined

Question 13

During isometric contraction of a skeletal-muscle fiber,tension increases but the fiber length stays the same.

Accepted Answer

A) True 
 B)False

Question 14

John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest.Jim is a marathon runner who specializes in long,steady runs.Compared to Jim,John is likely to have:

Accepted Answer

A)  legs with a larger diameter.
B)  legs with a smaller diameter.
C)  hypertrophy of type I muscle fibers.
D)  a higher density of capillaries in his legs.
E)  lower concentrations of glycolytic enzymes in his leg muscles.F) B) and E)
G) A) and D)

Question 15

Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.

Accepted Answer

A) True 
 B)False

Question 16

The optimal length (Lo) of a skeletal muscle cell is:

Accepted Answer

A)  the length at which the muscle can generate its maximum tetanic tension.
B)  the shortest length the muscle can achieve while attached to bone,because the amount of overlap between thick and thin filaments is maximal then.
C)  generally the length attained when the joint it crosses is fully extended.
D)  the only length at which any tension can be generated by the muscle cell.
E)  the length at which thin filaments from opposite sides of a sarcomere overlap.F) D) and E)
G) A) and B)

Question 17

Which of the following statements regarding contraction in skeletal and smooth muscle is TRUE?

Accepted Answer

A)  In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding directly to myosin.
B)   In skeletal muscle,calcium ions bind to a regulatory protein on thin filaments; in smooth muscle,calcium ions bind to a regulatory protein on thick filaments.
C)  In skeletal muscle,calcium initiates contraction by binding to myosin light-chain kinase,while in smooth muscle calcium initiates contraction by binding directly to tropomyosin.
D)  In skeletal muscle,calcium initiates contraction by binding to troponin,while in smooth muscle calcium initiates contraction by binding to calmodulin.
E)   All of the choices are true.F) D) and E)
G) All of the above

Question 18

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 19

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 20

Which of the following statements about different kinds of skeletal-muscle fibers is TRUE?

Accepted Answer

A)  Slow-oxidative fibers have a greater abundance of glycogen than do fast-glycolytic fibers.
B)  Fast-glycolytic fibers have a greater abundance of myoglobin than do slow-oxidative fibers.
C)  A fast-glycolytic fiber can generate greater tension than a slow-oxidative fiber.
D)  Fast-glycolytic fibers and slow-oxidative fibers are innervated by alpha motor neurons of the same diameter.
E)  To generate ATP,fast-glycolytic fibers depend mainly on oxidative phosphorylation while slow-oxidative fibers depend mainly on glycolysis.F) A) and E)
G) None of the above

Exam 9: Muscle

Which of the following statements about different kinds of skeletal-muscle fibers is TRUE?

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

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

Correct AnswerverifiedShow Answer

The optimal length (Lo) of a skeletal muscle cell is:

Correct AnswerverifiedShow Answer

Which is a TRUE statement about excitation-contraction coupling?

Correct AnswerverifiedShow Answer

Fast fibers can be distinguished from slow fibers by the rate at which their myosin-ATPases split ATP.

Correct AnswerverifiedShow Answer

During isometric contraction of a skeletal-muscle fiber,tension increases but the fiber length stays the same.

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 statements regarding myosin in skeletal muscle is TRUE?

Correct AnswerverifiedShow Answer

John is a sprinter who specializes in quick and powerful bursts of speed followed by periods of rest.Jim is a marathon runner who specializes in long,steady runs.Compared to Jim,John is likely to have:

Correct AnswerverifiedShow Answer

During skeletal-muscle contraction,the distance between the Z lines of a sarcomere decreases because of shortening of the filaments.

Correct AnswerverifiedShow Answer

Organophosphate "nerve gases" induce paralysis by blocking neural stimulation of the neuromuscular junctions,while botulinum toxin produces the same effect by inhibiting acetylcholinesterase.

Correct AnswerverifiedShow Answer

Which type of skeletal muscle fibers is generally recruited first?

Correct AnswerverifiedShow Answer

Which of the following statements regarding contraction in skeletal and smooth muscle is TRUE?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Fast-glycolytic muscle fibers differ from slow-oxidative fibers in that:

Correct AnswerverifiedShow Answer

Actin is an ATPase enzyme.

Correct AnswerverifiedShow Answer

The name given to the repeating functional units that cause striations in a skeletal muscle myofibril is "sarcomere."

Correct AnswerverifiedShow Answer

The site of Ca2+ storage in muscle cells is the lateral sacs of the transverse tubules.

Correct AnswerverifiedShow Answer

The force-generating sites in a myofibril are the Z lines.

Correct AnswerverifiedShow Answer

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The optimal length (L_o) of a skeletal muscle cell is:

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The site of Ca²⁺ storage in muscle cells is the lateral sacs of the transverse tubules.

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