Question 1

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.

Question 2

How is the length of a skeletal muscle cell related to the force it can generate?

Accepted Answer

A)  The tension in a skeletal muscle cell is greatest when contractions occur at either very short or very long lengths.
B)  Skeletal muscle cells generate the same amount of force,regardless of their length.
C)  The shorter a skeletal muscle cell is when it begins to contract,the stronger the force generation will be.
D)  The longer a skeletal muscle cell is when it begins to contract,the stronger the force generation will be.
E)  Skeletal muscle cells generate the most force when the contraction occurs at an intermediate length.

Question 3

Multiunit smooth-muscle cells

Accepted Answer

A)  generally have individual innervation of each cell.
B)  have many gap junctions between cells.
C)  respond to stretch by relaxing.
D)  can only be excited,and not inhibited.
E)  have abundant T-tubules.

Question 4

Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca2+.

Accepted Answer

A) True 
 B)False

Question 5

Fast myosin ATPase activity is typical of which type of skeletal muscle fibers?

Accepted Answer

A)  Type I
B)  Type II

Question 6

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 7

If a biopsy of the quadriceps (thigh extensor) muscles were taken from gold medal-winning speed skaters in the 4 events below,which would most likely have the SMALLEST percentage of type I muscle fibers?
Rev: 11_02_2012

Accepted Answer

A)  10,000 meters
B)  5,000 meters
C)  1,000 meters
D)  500 meters

Question 8

The energy for muscle contraction is provided indirectly by the hydrolysis of ATP.

Accepted Answer

A) True 
 B)False

Question 9

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 10

Flexor muscles generally pull on bone and decrease the angle at a joint,whereas extensor muscles push the bone to increase the angle.

Accepted Answer

A) True 
 B)False

Question 11

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

Accepted Answer

A)  Type I
B)  Type II A

Question 12

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 John's muscles,how are Jim's most likely to differ?

Accepted Answer

A)  Jim's muscles will have more glycogen stored in his type II b muscle fibers.
B)  Jim's muscles will have more mitochondria in his type I and II a muscle fibers.
C)  Jim's muscles will have less myoglobin in his type I muscle fibers.
D)   Jim's type II b fibers will be larger in diameter.
E)  Jim will have a greater proportion of type II muscle fibers and a lower proportion of type I fibers than John.

Question 13

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 joint

Question 14

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.

Question 15

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

Accepted Answer

A) True 
 B)False

Question 16

Neuronal stimulation of skeletal muscle is always excitatory,whereas neuronal stimulation of smooth muscle may be excitatory or inhibitory.

Accepted Answer

A) True 
 B)False

Question 17

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 18

Why does breathing continue to be rapid and deep for a time after heavy exercise?
8-7-2013

Accepted Answer

A)   Extra oxygen is needed to eliminate lactic acid and restore muscle creatine phosphate and glucose concentrations.
B)  The respiratory system is slow to increase and decrease its function before and after exercise,which is why it takes awhile for breathing to slow down.
C)  Lactic acid that builds up during heavy exercise must be exhaled into the air,so heavy breathing must continue for awhile after exercise to eliminate it.
D)  The ATP level in muscle cells falls drastically during heavy exercise,and extra oxygen is needed to restore it.
E)  The extra ventilation is not needed to replenish energy stores in muscle fibers,but rather simply to restore the blood pH to normal after the production of excess lactic acid during the exercise. A

Question 19

Which type of skeletal muscle fiber typically has less myoglobin?

Accepted Answer

A)  Type I
B)  Type II

Question 20

Which of the following statements is FALSE?

Accepted Answer

A)  Synaptic input onto skeletal muscle cells is always excitatory,whereas inputs to smooth muscle cells may be either excitatory or inhibitory.
B)  A single smooth-muscle cell may be innervated by both a sympathetic neuron and a parasympathetic neuron.
C)  Contractile activity of smooth-muscle cells does not normally require Ca2+.
D)  In the absence of any neural input,skeletal muscle cannot generate tension.
E)  Ca2+ that activates contraction of smooth muscles can come from either the ECF or from the sarcoplasmic reticulum. C

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

How is the length of a skeletal muscle cell related to the force it can generate?

Correct AnswerverifiedShow Answer

Multiunit smooth-muscle cells

Correct AnswerverifiedShow Answer

Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca2+.

Correct AnswerverifiedShow Answer

Fast myosin ATPase activity is typical of which type of skeletal muscle fibers?

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

If a biopsy of the quadriceps (thigh extensor) muscles were taken from gold medal-winning speed skaters in the 4 events below,which would most likely have the SMALLEST percentage of type I muscle fibers? Rev: 11_02_2012

Correct AnswerverifiedShow Answer

The energy for muscle contraction is provided indirectly by the hydrolysis of ATP.

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

Flexor muscles generally pull on bone and decrease the angle at a joint,whereas extensor muscles push the bone to increase the angle.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedA

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 John's muscles,how are Jim's most likely to differ?

Correct AnswerverifiedShow Answer

What is the definition of a "motor unit?"

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Neuronal stimulation of skeletal muscle is always excitatory,whereas neuronal stimulation of smooth muscle may be excitatory or inhibitory.

Correct AnswerverifiedShow Answer

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

Correct AnswerverifiedShow Answer

Why does breathing continue to be rapid and deep for a time after heavy exercise? 8-7-2013

Correct AnswerverifiedA

Which type of skeletal muscle fiber typically has less myoglobin?

Correct AnswerverifiedShow Answer

Which of the following statements is FALSE?

Correct AnswerverifiedC

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Binding of myosin to actin in skeletal muscle cells does not normally take place in the absence of Ca²⁺.

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A

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C