Question 1

Movements of the body are usually smooth and occur at differing rates because

Accepted Answer

A)   they are a mixture of isotonic and isometric contractions.
B)   motor units contract out of phase at their own particular rates.
C)   most muscle contractions closely resemble individual muscle twitches.
D)   muscles of different sizes contract at different rates.
E)   of the all or none principle.F) B) and D)
G) D) and E)

Question 2

-What does "B" represent on the diagram?

Accepted Answer

A)   myosin myofilament
B)   actin myofilament
C)   sarcomere
D)   Z disk
E)   cross-bridgeF) A) and B)
G) B) and C)

Question 3

Which of the following events occurs on the postsynaptic membrane?

Accepted Answer

A)   acetylcholine production
B)   rapid degradation of acetylcholine
C)   release of neurotransmitter
D)   neurotransmitter combines with a receptor molecule
E)   release of calcium ionsF) B) and D)
G) B) and C)

Question 4

Myosin phosphatase

Accepted Answer

A)   activates myosin kinase.
B)   forms the cross-bridge.
C)   removes phosphate from myosin.
D)   binds to calcium-calmodulin complex.
E)   opens calcium channels.F) B) and D)
G) D) and E)

Question 5

Skeletal muscle fibers

Accepted Answer

A)   possess striations.
B)   can contract but are not extensible or excitable.
C)   do not require nerve innervation to contract.
D)   increase dramatically in number after birth.
E)   are found in the walls of the stomach.F) B) and E)
G) A) and C)

Question 6

Which of the following events occurs during the lag phase of a muscle twitch?

Accepted Answer

A)   Muscle fibers shorten.
B)   Cross-bridges form, move, release, and reform many times.
C)   The action potential is propagated from presynaptic to postsynaptic membrane.
D)   Calcium is pumped back into the sarcoplasmic reticulum.
E)   All of these events occur in the lag phase.F) B) and D)
G) A) and B)

Question 7

In smooth muscle, cross-bridging occurs due to

Accepted Answer

A)   calcium binding to troponin.
B)   calcium binding to calmodulin.
C)   myosin kinase adding a phosphate to myosin heads.
D)   both calcium binding to troponin and calmodulin.
E)   both calcium binding to calmodulin and myosin kinase adding a phosphate to myosin heads.F) C) and E)
G) A) and C)

Question 8

What is tropomyosin?

Accepted Answer

A)   a protein found along the groove of the F-actin double helix
B)   a T tubule and two adjacent terminal cisternae
C)   the combination of myosin heads with active sites on actin molecules
D)   the movement of myosin head while attached to actin myofilament
E)   after exercise, the oxygen taken in that exceeds the oxygen required for resting metabolismF) C) and D)
G) A) and E)

Question 9

Which of the following situations occurs in electrically excitable cells?

Accepted Answer

A)   When Na+ ion channels open, K+ ion channels close.
B)   The sodium-potassium pump moves sodium into the cell.
C)   Depolarization causes voltage-gated sodium ion channels to open.
D)   Sodium ion channels are opened by high extracellular calcium levels.
E)   The opening and closing of ligand-gated channels cause depolarization.F) A) and D)
G) C) and E)

Question 10

Which of the following statements concerning smooth muscle is true?

Accepted Answer

A)   It contains many sarcomeres.
B)   Caveolae seem to take the place of the myofibrils.
C)   A calcium-calmodulin complex initiates cross-bridge formation.
D)   The cells are large and multinuclear.
E)   It has a well developed sarcoplasmic reticulum.F) B) and C)
G) A) and E)

Question 11

A muscle fiber will respond to a stimulus when that stimulus reaches the _____ level.

Accepted Answer

A)   threshold
B)   relaxation
C)   rigor mortis
D)   recruitment
E)   restingF) B) and D)
G) All of the above

Question 12

A myofibril is the

Accepted Answer

A)   cell membrane of a muscle fiber.
B)   cytoplasm of muscle cells.
C)   structural and functional unit of the skeletal muscle cell.
D)   contractile thread that extends the length of the muscle fiber.
E)   protein strand composed of actin.F) C) and D)
G) A) and D)

Question 13

-What does "B" represent on the diagram?

Accepted Answer

A)   threshold
B)   depolarization
C)   depolarization phase of action potential
D)   repolarization phase of action potentialE) B) and C)
F) A) and B)

Question 14

Which of the following will respond to a threshold stimulus with an all-or-none contraction?

Accepted Answer

A)   a single muscle fiber
B)   a single motor unit
C)   a whole muscle
D)   a single muscle fiber and a single motor unit
E)   a single muscle fiber, a single motor unit, and a whole muscleF) A) and C)
G) B) and D)

Question 15

Which of the following would occur as a result of a single muscle contraction?

Accepted Answer

A)   tetanus
B)   tone
C)   treppe
D)   twitch
E)   paralysisF) A) and E)
G) A) and D)

Question 16

During the contraction phase of a muscle twitch,

Accepted Answer

A)   acetylcholine stimulates the pre-synaptic terminal.
B)   sodium ions diffuse into the muscle fiber.
C)   actin-myosin cross-bridges form.
D)   calcium ions are transported back to the sarcoplasmic reticulum.
E)   the action potential travels down the T tubule.F) A) and E)
G) B) and E)

Question 17

In excitation-contraction coupling,

Accepted Answer

A)   calcium ions must bind with myosin to expose active sites on actin.
B)   myosin heads bind to exposed active sites on actin.
C)   cross-bridges form between myosin heads and calcium ions.
D)   movement of the troponin-tropomyosin complex causes actin myofilaments to slide.
E)   ATP binds to actin myofilaments.F) B) and E)
G) A) and E)

Question 18

Muscle atrophy

Accepted Answer

A)   involves an increase in the number of muscle fibers.
B)   is characterized by a decrease in muscle size.
C)   results from aerobic exercise.
D)   causes an increase in blood flow to the affected muscle.
E)   is characterized by an increase in muscle size.F) B) and E)
G) A) and B)

Question 19

If sodium ions cannot enter a muscle fiber in response to a stimulus,

Accepted Answer

A)   contraction cannot occur.
B)   relaxation cannot occur.
C)   sodium ions will be released from the sarcoplasmic reticulum instead.
D)   the active sites are left exposed.
E)   the action potential travels into the muscle anyway.F) B) and E)
G) A) and E)

Question 20

Identify the statement concerning general functional characteristics of muscle that is true.

Accepted Answer

A)   Muscle tissue shortens forcefully but lengthens passively.
B)   Muscle tissue shortens passively but lengthens forcefully.
C)   Muscle tissue can get shorter, but can not get longer.
D)   Muscle tissue can get longer, but can not get shorter.
E)   None of these statements are true.F) A) and E)
G) B) and E)

Exam 9: Muscular System: Histology and Physiology

During the contraction phase of a muscle twitch,

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-What does "B" represent on the diagram?

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Identify the statement concerning general functional characteristics of muscle that is true.

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What is tropomyosin?

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If sodium ions cannot enter a muscle fiber in response to a stimulus,

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Which of the following will respond to a threshold stimulus with an all-or-none contraction?

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In smooth muscle, cross-bridging occurs due to

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Skeletal muscle fibers

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Which of the following situations occurs in electrically excitable cells?

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Movements of the body are usually smooth and occur at differing rates because

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A myofibril is the

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Which of the following events occurs during the lag phase of a muscle twitch?

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A muscle fiber will respond to a stimulus when that stimulus reaches the _____ level.

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Muscle atrophy

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Which of the following would occur as a result of a single muscle contraction?

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Myosin phosphatase

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Which of the following statements concerning smooth muscle is true?

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In excitation-contraction coupling,

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Which of the following events occurs on the postsynaptic membrane?

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-What does "B" represent on the diagram?

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