Which of the following terms are NOT used interchangeably?
motor unit – motor neuron
Which of the following is NOT a phase of a muscle twitch?
shortening phase
Where does the acetylcholine that stimulates muscle contraction bind?
receptors in the motor end plate
When acetylcholine binds to its receptors, it results in __________.
the end plate potential, a graded depolarization, and a change in ion permeability
Which of the following occurs during the latent period of muscle contraction?
Calcium is released from the sarcoplasmic reticulum.
As the stimulus voltage was increased in this activity, which of the following occurred?
The muscle force generated increased.
Which of the following describes the relaxation phase?
The sarcomeres are increasing in length, and the force generated decreases.
Which of the following can trigger a muscle twitch?
release of acetylcholine or electrical stimulation
Which of the following is proportional to the amount of tension produced by a skeletal muscle?
the number of motor units activated
NO force is generated during which of the following?
the latent period
What is the minimum voltage needed to generate active force in the skeletal muscle?
threshold voltage
A motor unit is defined as _______.
the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates
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
Increasing the applied voltage in the simulation corresponds to which in vivo event?
motor unit recruitment
As the stimulus voltage increased, the resulting muscle tension _____.
increased to a point until it reached a plateau
Which of the following occurs during the contraction phase?
Cross-bridge cycling is taking place.
Treppe is the phenomenon that results in _______.
a progressive increase in the force generated with repetitive stimulation
When the frequency of stimulation of a muscle is great enough, _______.
wave summation results and muscle twitches overlap.
When wave summation occurs, _______.
the muscle force generated increases
Why does wave summation occur?
Muscle fibers are partially contracted when the next stimulus arrives.
Which of the following produced an increase in stimulus intensity?
increasing the voltage applied
Which of the following produced an increase in stimulus frequency?
clicking the mouse in rapid succession
Which of the following does NOT describe treppe?
An increase in stimulus intensity is required to see the effect.
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.
The resting length of the muscle _______.
occurs when the muscle is relaxed
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
Which of the following is generated when cross-bridges form between actin and myosin?
active force
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.
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.
Which starting length of the muscle provided the maximum total force?
the longest starting length
At which muscle length was the passive force the greatest?
100 mm

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