Deck 14: Skeletal Muscle Physiology: Frogs and Human Subjects

Question 1

A muscle twitch is .

A)a twinge that one feels in an isolated muscle
B)the maximal force a muscle can generate
C)a single contraction of skeletal muscle
D)an action potential in a muscle

Answer 1

C

Question 2

A motor unit is _.

A)a period of time during muscle contraction
B)all the axons of nerve cells that innervate a muscle
C)a single motor neuron and all the muscle cells it innervates
D)a group of linked muscle cells

Answer 2

C

Question 3

Place the following events in the correct sequence in which they occur: excitation- contraction coupling, electrical excitation of the muscle cell membrane, sliding of the myofilaments.

A)electrical excitation of the muscle cell membrane, excitation- contraction coupling, sliding of the myofilaments
B)electrical excitation of the muscle cell membrane, sliding of the myofilaments, excitation- contraction coupling
C)sliding of the myofilaments, electrical excitation of the muscle cell membrane, excitation- contraction coupling
D)excitation- contraction coupling, sliding of myofilaments, electrical excitation of the muscle cell membrane

Answer 3

A

Question 4

At this stimulus strength, all muscle cells of a particular muscle are being stimulated.

A)subthreshold stimulus
B)maximal stimulus
C)threshold stimulus

Question 5

The stimulus from motor neuron to neuromuscular junction is _, and the stimulus from axon terminal to muscle sarcolemma is .

A)chemical, electrical
B)electrical, chemical
C)chemical, chemical
D)electrical, electrical

Question 6

From your own experience, predict the relative times to fatigue of a subject's upper limb muscles as they hold a light book or a very heavy book in front of them.

A)The heavy book causes earliest fatigue.
B)Book weight is unrelated to time of fatigue.
C)It will take hours for either book to cause fatigue.
D)The light book causes earliest fatigue.

Question 7

According to its definition, muscle fatigue is .

A)a muscle that begins to "burn" as you exercise
B)a tired muscle
C)the physiological inability of a muscle to contract
D)an irreversible condition brought about by strong stimulus to a muscle

Question 8

Which event requires multiple stimuli?

A)both muscle twitch and tetanus
B)tetanus
C)muscle twitch

Question 9

When a muscle cell is at rest, there is a charge separation (voltage)across the plasma membrane called .

A)the resting membrane potential
B)depolarization
C)the battery
D)repolarization

Question 10

During an action potential in muscle, _ .

A)Na+ diffuses into the cell, then K+ diffuses out
B)K+ diffuses into the cell, then Na+ diffuses out
C)both Na+ and K+ diffuse into the cell
D)both Na+ and K+ diffuse out of the cell

Question 11

The rising phase of a muscle twitch represents .

A)the time between stimulus and active muscle contraction
B)the time of relaxation of the muscle fibers
C)the time of shortening of the sarcomeres of the muscle fibers

Question 12

Most subjects use their dominant forearm far more than their nondominant forearm. How might the dominant forearm differ physiologically or structurally from the nondominant forearm?

A)The muscle fibers may be larger, and contract more efficiently.
B)Psychological factors may result in increased force being generated.
C)There may be a great increase in the number of muscle fibers.

Question 13

An action potential is _ .

A)a refractory period of the cell membrane
B)a depolarization of the cell membrane
C)a rapid depolarization and repolarization of the cell membrane that is propagated
D)a repolarization of the cell membrane

Question 14

Your friend has a paralyzed arm. What physical events might have caused this?

A)Any of these events could have caused the paralysis: damage to the part of the brain that controls that arm, damage to the part of the spinal cord that controls that arm, or drug- induced failure at the neuromuscular junction.
B)damage to the part of the brain that controls that arm
C)damage to the part of the spinal cord that controls that arm
D)drug- induced failure at the neuromuscular junction

Question 15

When muscle is stimulated directly to contract, does the rising phase of the twitch begin immediately? If not, why not?

A)No, electrical and chemical changes at the muscle membrane must occur before contraction.
B)No, the rising phase occurs only after a substantial number of muscle fibers have contracted.
C)No, the falling phase of the twitch must occur first.
D)Yes, it does begin immediately.

Question 16

The maximum force that can be attained by a contracting muscle occurs during .

A)fused tetanus
B)a maximal twitch
C)low frequency wave summation

Question 17

Graded muscle contractions .

A)represent increasing amounts of force generated by a muscle, depend on activation of more and more motor units, and depend on increasing frequency of nerve action potentials to each motor unit
B)depend on activation of more and more motor units
C)depend on increasing frequency of nerve action potentials to each motor unit
D)represent increasing amounts of force generated by a muscle

Question 18

This ion is critical for normal excitation- contraction coupling, but is not necessary for contraction of the glycerinated muscle fibers you worked with in the lab.

A)Na+
B)K+
C)Mg2+
D)Ca2+

Question 19

In the glycerinated muscle, these substances are necessary for maximal contraction to occur.

A)ATP only
B)K+ and Mg2+
C)ATP, K⁺, and Mg²⁺ D)ATP and Ca²⁺

Question 20

The gradual activation of more and more motor units is called .

A)raw EMG
B)dynagram
C)wave summation
D)recruitment

Question 21

When the nerve to a muscle is destroyed, _.

A)the muscle will continue to contract weakly
B)the muscle can continue to contract normally or it can continue to contract weakly
C)the muscle will no longer contract
D)the muscle will continue to contract normally

Question 22

In your lab exercise, how many electrodes are used to record the electrical activity of muscles of the forearm?

A)3
B)2
C)4
D)1

Question 23

In your laboratory experiments, you most often observed .

A)isometric contractions
B)both isotonic and isometric contractions
C)neither isotonic nor isometric contractions
D)isotonic contractions

Question 24

An electromyogram is .

A)an instrument used to record the electrical activity of muscles
B)a visual recording of the force generated by muscle contraction
C)a graphic representation of the voltage waveforms associated with muscle contraction
D)a device used to measure the force of muscle activity

Question 25

What causes muscle contractions to be graded?

A)increasing stimulus frequency
B)both increasing stimulus strength and increasing stimulus frequency
C)increasing stimulus strength