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Which of the following terms are NOT used interchangeably |
motor unit – motor neuron |
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Which of the following is NOT a phase of a muscle twitch |
shortening phase |
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Where does the acetylcholine that stimulates muscle contraction bind? |
receptors in the motor end plate |
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When acetylcholine binds to its receptors, it results in __________. |
the end plate potential, a graded depolarization, and a change in ion permeability |
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Which of the following occurs during the latent period of muscle contraction |
Calcium is released from the sarcoplasmic reticulum. |
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As the stimulus voltage was increased in this activity, which of the following occurred? |
The muscle force generated increased |
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Which of the following describes the relaxation phase? |
The sarcomeres are increasing in length, and the force generated decreases |
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Which of the following can trigger a muscle twitch? |
release of acetylcholine or electrical stimulation |
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Which of the following is proportional to the amount of tension produced by a skeletal muscle? |
the number of motor units activated |
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NO force is generated during which of the following? |
the latent period |
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What is the minimum voltage needed to generate active force in the skeletal muscle |
threshold voltage |
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A motor unit is defined as _______. |
the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates |
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In the lab, a researcher finds that the threshold stimulus to induce an action potential in a muscle fiber’s sarcolemma was 3.0 volts. Which of the following would result in muscle tension? |
3.0 volts and 4.0 volts |
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Increasing the applied voltage in the simulation corresponds to which in vivo event? |
motor unit recruitment |
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As the stimulus voltage increased, the resulting muscle tension _______. |
increased to a point until it reached a plateau |
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Which of the following occurs during the contraction phase? |
Cross-bridge cycling is taking place. |
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Treppe is the phenomenon that results in _______. |
a progressive increase in the force generated with repetitive stimulation |
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When the frequency of stimulation of a muscle is great enough, _______. |
wave summation results and muscle twitches overlap. |
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When wave summation occurs, _______. |
the muscle force generated increases |
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Why does wave summation occur? |
Muscle fibers are partially contracted when the next stimulus arrives. |
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Which of the following produced an increase in stimulus intensity? |
increasing the voltage applied |
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Which of the following produced an increase in stimulus frequency? |
clicking the mouse in rapid succession |
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Which of the following does NOT describe treppe? |
An increase in stimulus intensity is required to see the effect. |
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Which of the following does NOT describe tetanus? |
The muscle relaxes fully between contractions. |
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Which of the following is true of the maximum stimulus frequency? |
No greater muscle force can be generated and the muscle has reached maximal tetanic tension. |
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Muscle twitches overlap with _______. |
both fused and unfused tetanus |
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Which of the following would result in fused or unfused tetanus? |
increasing the stimulus frequency |
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To transition from unfused tetanus to fused tetanus, _______. |
stimulus frequency increased |
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Which of the following describes the relationship between stimulus frequency and muscle tension? |
When stimulus frequency increases, muscle tension increases to a maximum value. |
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At what stimulus frequency was maximal tetanic tension developed? |
146 stimuli/sec |
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Which of the following occurs if the load attempted is equal to or greater than the force generated by a muscle? |
Isometric muscle contraction occurs |
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The resting length of the muscle _______. |
occurs when the muscle is relaxed |
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The graph of the length-tension relationship illustrates _______. |
the optimal sarcomere length for muscle contraction and the amount of overlap between the thick and thin filaments in the resting muscle |
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Which of the following is generated when cross-bridges form between actin and myosin? |
active force |
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Which of the following describes the relationship between length and tension? |
The active force can increase or decrease, depending on the starting resting length of the muscle. |
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Why does the active force of skeletal muscle change with the muscle’s resting length? |
The number of cross-bridges between actin and myosin varies. |
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Which starting length of the muscle provided the maximum total force? |
the longest starting length |
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At which muscle length was the passive force the greatest? |
100 mm |
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Which of the following occurs during isotonic concentric contraction? |
The length of the muscle decreases with contraction. |
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Which of the following occurs during the latent period of isotonic concentric contraction? |
Muscle tension is produced, and the weight will not move. |
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The speed of muscle contraction is called the _______. |
shortening velocity |
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For a weight to be lifted, which of the following must occur? |
An isotonic muscle contraction with a force greater than the load. |
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When the load to be lifted increases in weight, the latent period _______. |
increases |
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The shortest duration of muscle contraction occurs with _______. |
heaviest load |
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The velocity of shortening _______. |
decreased as the weight increased and increased as the weight decreased |
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As the weight increased, the distance the weight was lifted _______. |
decreased until the weight was not moved at all |
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