Muscular System: Histology and Physiology

Question 1

Which of these is true of skeletal muscle?

a. spindle-shaped cells
b. under involuntary control
c. many peripherally located nuclei per muscle fiber
d. forms the walls of hollow internal organs
e. may be autorhythmic

Answer 1

many peripherally located nuclei per muscle fiber

Question 2

Which of these is not a major property of muscle?

a. contractility
b. elasticity
c. excitability
d. extensibility
e. secretability

Answer 2

secretability

Question 3

Given these structures:

(1) whole muscle
(2) muscle fiber (cell)
(3) myofilament
(4) myofibril
(5) muscle fasciculus

Choose the arrangement that lists the structures in the correct order from largest to smallest.

Answer 3

1,5,2,4,3

Question 4

Each myofibril

a. is made up of many muscle fibers.
b. contains sarcoplasmic reticulum.
c. is made up of many sarcomeres.
d. contains T tubules.
e. is the same thing as a muscle fiber.

Answer 4

is made up of many sarcomeres

Question 5

Myosin myofilaments are

a. attached to the Z disk.
b. found primarily in the I band.
c. thinner than actin myofilaments.
d. absent from the H zone.
e. attached to filaments that form the M line.

Answer 5

attached to filaments that form the M line

Question 6

Which of these statements about the molecular structure of myofila-ments is true?

a. Tropomyosin has a binding site for Ca2+.
b. The head of the myosin molecule binds to an active site on G actin.
c. ATPase is found on troponin.
d. Troponin binds to the rodlike portion of myosin.
e. Actin molecules have a hingelike portion, which bends and straightens during contraction.

Answer 6

the head of the myosin molecule binds to an active site on G actin

Question 7

The part of the sarcolemma that invaginates into the interior of skel-etal muscle fibers is the

Answer 7

T tubule system

Question 8

During the depolarization phase of an action potential, the permeabil-ity of the plasma membrane to

Answer 8

Na+ increases

Question 9

During repolarization of the plasma membrane,

Answer 9

K+ moves to the outside of the cell

Question 10

Given these events:
(1) Acetylcholine is broken down into acetic acid and choline.
(2) Acetylcholine diffuses across the synaptic cleft.
(3) An action potential reaches the terminal branch of the motor neuron.
(4) Acetylcholine combines with a ligand-gated ion channel.
(5) An action potential is produced on the muscle fiber’s plasma membrane.
Choose the arrangement that lists the events in the order they occur at a neuromuscular junction.

Answer 10

3,2,4,5,1

Question 11

Acetylcholinesterase is an important molecule in the neuromuscular junction because it

a. stimulates receptors on the presynaptic terminal.
b. synthesizes acetylcholine from acetic acid and choline.
c. stimulates receptors within the postsynaptic membrane.
d. breaks down acetylcholine.
e. causes the release of Ca2+ from the sarcoplasmic reticulum.

Answer 11

breaks down acetylcholine

Question 12

Given these events:
(1) The sarcoplasmic reticulum releases Ca2+.
(2) The sarcoplasmic reticulum takes up Ca2+.(3) Calcium ions diffuse into the sarcoplasm.
(4) An action potential moves down the T tubule.
(5) The sarcomere shortens.
(6) The muscle relaxes.
Choose the arrangement that lists the events in the order they occur following a single stimulation of a skeletal muscle fiber.

Answer 12

4,1,3,5,2,6

Question 13

Given these events:
(1) Calcium ions combine with tropomyosin.
(2) Calcium ions combine with troponin.
(3) Tropomyosin pulls away from actin.
(4) Troponin pulls away from actin.
(5) Tropomyosin pulls away from myosin.
(6) Troponin pulls away from myosin.
(7) Myosin binds to actin.
Choose the arrangement that lists the events in the order they occur during muscle contraction.

Answer 13

2,3,7

Question 14

With stimuli of increasing strength, which of these is capable of a graded response?

a. neuron axon
b. muscle fiber
c. motor unit
d. whole muscle

Answer 14

whole muscle

Question 15

Considering the force of contraction of a skeletal muscle fiber, multiple-wave summation occurs because of

a. increased strength of action potentials on the plasma membrane.
b. a decreased number of cross-bridges formed.
c. an increase in Ca2+ concentration around the myofibrils.
d. an increased number of motor units recruited.
e. increased permeability of the sarcolemma to Ca2+.

Answer 15

an increase in Ca2+ concentration around the myofibrils

Question 16

Which of these events occurs during the lag (latent) phase of muscle contraction?

a. cross-bridge movement
b. active transport of Ca2+ into the sarcoplasmic reticulum
c. Ca2+ binding to troponin
d. sarcomere shortening
e. breakdown of ATP to ADP

Answer 16

Ca2+ binding to troponin

Question 17

A weight lifter attempts to lift a weight from the floor, but the weight is so heavy that he is unable to move it. The type of muscle contrac-tion the weight lifter is using is mostly

Answer 17

isometric