Question 1

A lack of ATP in the muscle cell will lead to

Accepted Answer

A)  calcium build-up in the cytosol.
B)  myosin heads becoming "stuck" in a bound configuration with actin.
C)  troponin unbinding from tropomyosin.
D)  frequent twitches with short periods of relaxation in between.
E)  sustained flaccid paralysis.F) A) and E)
G) None of the above

Question 2

A Ca²⁺-binding protein in smooth muscle is calmodulin.

Accepted Answer

A) True 
 B)False

Question 3

Which of these is a major difference between smooth muscle and skeletal muscle?

Accepted Answer

A)  Myosin is the main regulatory protein in smooth muscle.
B)  Myosin is the main regulatory protein in skeletal muscle.
C)  Skeletal muscle usually exhibits spontaneous activity,while smooth muscle cannot contract spontaneously. 
D)  Only skeletal muscle requires increased calcium ion concentration in the cytosol for contraction.
E)  Only skeletal muscle has both actin and myosin.F) None of the above
G) A) and B)

Question 4

Endurance exercise,such as long-distance swimming,causes a preferential increase in glycolytic enzymes and increased mass of the exercising muscles.

Accepted Answer

A) True 
 B)False

Question 5

The myosin in smooth muscle cells differs from that in skeletal muscle in that smooth muscle myosin requires phosphorylation before it can bind to actin.

Accepted Answer

A) True 
 B)False

Question 6

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

Accepted Answer

A) True 
 B)False

Question 7

Type 2 muscle fibers typically have the fewer mitochondria than type 1.

Accepted Answer

A) True 
 B)False

Question 8

You have designed a drug that is supposed to bind to the myosin binding sites on actin.You inject it into a relaxed muscle,but find that none of the drug bound.Which of the following explains why?

Accepted Answer

A)  There are no myosin binding sites on actin.
B)  Troponin molecules are covering myosin binding sites on actin.
C)  The myosin binding sites are covered by ATP.
D)  The myosin binding sites on actin are covered by tropomyosin.
E)  None of the choices are correct.F) C) and D)
G) A) and E)

Question 9

In skeletal muscle cells,calcium initiates contraction by binding to

Accepted Answer

A)  tropomyosin.
B)  actin.
C)  troponin.
D)  myosin.
E)  the thick filament.F) None of the above
G) C) and E)

Question 10

Ca²⁺ or any other positive ion can enable cross-bridge cycling to begin.

Accepted Answer

A) True 
 B)False

Question 11

What is the best description of a tetanic contraction in a skeletal muscle cell?

Accepted Answer

A)  A single action potential in the motor neuron causes a sustained contraction.
B)  Multiple action potentials in the motor neuron cause a sustained contraction.
C)  The action potential in the muscle cell is prolonged to last as long as the contraction.
D)  Repeated action potentials from the motor neuron summate into a sustained depolarization of the motor end plate,causing a sustained contraction.
E)  A very large amplitude action potential in the motor neuron causes a very strong contraction in the skeletal muscle cell.F) All of the above
G) A) and E)

Question 12

What is the definition of a "motor unit"?

Accepted Answer

A)  A single motor neuron plus all the muscle fibers it innervates
B)  A single muscle fiber plus all of the motor neurons that innervate it
C)  All of the motor neurons supplying a single muscle
D)  A pair of antagonistic muscles
E)  All of the muscles that affect the movement of any given jointF) All of the above
G) A) and D)

Question 13

What protein is the principal component of skeletal muscle thick filaments?

Accepted Answer

A)  Actin
B)  Myosin
C)  Troponin
D)  Calmodulin
E)  TropomyosinF) C) and D)
G) A) and E)

Question 14

Characteristics of slow-oxidative fibers include numerous mitochondria,abundant myoglobin,and large stores of glycogen.

Accepted Answer

A) True 
 B)False

Question 15

The muscles in your fingers have a predominance of fast-glycolytic fibers,whereas the muscles of your feet have a predominance of slow-oxidative fibers.Which of the following statements accurately describes their differences?

Accepted Answer

A)  The muscle fibers of the feet have a greater abundance of glycogen than do the muscle fibers of the hands.
B)  Muscle fibers of the feet have a greater abundance of myoglobin than do muscle fibers of the hands.
C)  Muscle fibers of the hands can generate greater tension than muscle fibers of the feet.
D)  Muscle fibers in both locations are innervated by alpha motor neurons of the same diameter.
E)  More oxidative phosphorylation occurs in the hands than the feet.F) None of the above
G) All of the above

Question 16

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 E)

Question 17

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

Accepted Answer

A) True 
 B)False

Question 18

What would be the result if the administration of a drug sequesters all the ATP in a cell?

Accepted Answer

A)  All cross-bridges will remain tightly bound to actin.
B)  Calcium will remain in the cytosol,continuously stimulating cross-bridge cycling.
C)  Repeated,high-frequency action potentials will be fired at a skeletal muscle fiber causing sustained contraction.
D)  Calcium-activated proteases degrade all proteins in skeletal muscle fibers,making muscles limp.
E)  A build-up of K⁺ in T-tubules will cause constant,tetanic contractions of skeletal muscles.F) None of the above
G) B) and D)

Question 19

Which of the following statements regarding skeletal muscle is TRUE?

Accepted Answer

A)  Skeletal muscle fibers have pacemaker activity.
B)  Skeletal muscle fibers are joined together by gap junctions.
C)  A given skeletal muscle fiber will contract when excitatory nervous stimuli sufficiently exceed inhibitory nervous stimuli at the motor end plate.
D)  A given skeletal muscle fiber will contract if excitatory synaptic inputs sufficiently exceed inhibitory synaptic inputs on the motor neuron that innervates that fiber and the motor neuron fires an action potential.
E)  Skeletal muscle contraction is inhibited by inhibitory motor neurons that synapse onto skeletal muscle fibers.F) A) and B)
G) A) and C)

Question 20

Compared to type 1 (slow oxidative) skeletal muscle fibers,how are type 2X (fast-glycolytic) skeletal muscle fibers different?

Accepted Answer

A)  Type 2X fibers have more abundant mitochondria.
B)  Type 2X fibers fatigue more readily.
C)  Type 2X fibers have more abundant myoglobin.
D)  Type 2X fibers are smaller in diameter.
E)  Type 2X motor units contain fewer fibers per alpha motor neuron.F) C) and D)
G) B) and E)

Exam 9: Muscle

You have designed a drug that is supposed to bind to the myosin binding sites on actin.You inject it into a relaxed muscle,but find that none of the drug bound.Which of the following explains why?

Correct AnswerverifiedShow Answer

Which of the following statements regarding skeletal muscle is TRUE?

Correct AnswerverifiedShow Answer

A Ca²⁺-binding protein in smooth muscle is calmodulin.

Correct AnswerverifiedShow Answer

In skeletal muscle cells,calcium initiates contraction by binding to

Correct AnswerverifiedShow Answer

What is the definition of a "motor unit"?

Correct AnswerverifiedShow Answer

Type 2 muscle fibers typically have the fewer mitochondria than type 1.

Correct AnswerverifiedShow Answer

The myosin in smooth muscle cells differs from that in skeletal muscle in that smooth muscle myosin requires phosphorylation before it can bind to actin.

Correct AnswerverifiedShow Answer

Which of these is a major difference between smooth muscle and 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

The muscles in your fingers have a predominance of fast-glycolytic fibers,whereas the muscles of your feet have a predominance of slow-oxidative fibers.Which of the following statements accurately describes their differences?

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

What would be the result if the administration of a drug sequesters all the ATP in a cell?

Correct AnswerverifiedShow Answer

What protein is the principal component of skeletal muscle thick filaments?

Correct AnswerverifiedShow Answer

Ca²⁺ or any other positive ion can enable cross-bridge cycling to begin.

Correct AnswerverifiedShow Answer

A lack of ATP in the muscle cell will lead to

Correct AnswerverifiedShow Answer

Characteristics of slow-oxidative fibers include numerous mitochondria,abundant myoglobin,and large stores of glycogen.

Correct AnswerverifiedShow Answer

Compared to type 1 (slow oxidative) skeletal muscle fibers,how are type 2X (fast-glycolytic) skeletal muscle fibers different?

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

Endurance exercise,such as long-distance swimming,causes a preferential increase in glycolytic enzymes and increased mass of the exercising muscles.

Correct AnswerverifiedShow Answer

What is the best description of a tetanic contraction in a skeletal muscle cell?

Correct AnswerverifiedShow Answer

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