Lab Quiz

Skeletal Muscle Physiology Lab Quiz

This activity contains 25 questions.

	Refer to Activity 2: Determining the Latent Period. The latent period between time of innervation and time of contraction is:   0.55 msec. 1.36 msec. 1.84 msec. 2.78 msec. 3.12 msec.

	Refer to Activity 2. During the latent period, what is actually happening?   The electrochemical impulse is being transmitted. The muscle is recruiting myosin to the site of contraction. The sarcoplasmic reticulum is releasing calcium into the sarcoplasm. The actin and myosin filaments are sliding. Nothing is occurring.

	Refer to Activity 3: Investigating Graded Muscle Response to Increased Stimulus Intensity. What is the minimal or threshold stimulus?   0.2 volts 0.4 volts 0.6 volts 0.8 volts 1.0 volt

	Refer to Activity 3. The maximal stimulus is approximately:   10 volts 8 volts 6 volts 4 volts 2 volts

	Refer to Activity 3. The increase in force is a result of:   (a) more voltage being delivered to the whole muscle. (b) more muscle fibers being activated. (c) more calcium being absorbed. both (a) and (b) all of the above

	Refer to Question #5. This increase represents which type of summation?   Multiple motor unit summation Incomplete tetanus Complete tetanus Twitch Wave summation

	Refer to Activity 4: Investigating Treppe. With each subsequent stimulus, the force produced _____________ , provided the stimuli are delivered relatively close together.   decreases slightly increases slightly remains the same decreases greatly increases greatly

	Refer to Activity 5: Investigating Wave Summation. The peak force produced in the second contraction is ___________ that produced by the first stimulus.   greater than less than equal to produced by a different contraction mechanism than

	Refer to Activity 5. When the Single Stimulus button is clicked several times in rapid succession, the total force production:   Is even greater. decreases. remains the same. increases to a certain point, then plateaus. decreases, then begins to increase after several seconds.

	Refer to Activity 5. At Active Force = 2 gms, when the Single Stimulus button is clicked rapidly several times,   a smooth sustained contraction is produced. the twitch tracing rises and falls. the twitch tracing continues to rise. the force generated does not change. the twitch tracing plateaus.

	Refer to Activity 5. At Active Force = 3 gms,   the trace produces a single twitch. the trace is more erratic. the trace shows a flat line. the trace is smoother. the trace does not change from Active Force = 2 gms.

	Refer to Question #11. To this point, the maximal stimulus has been used. If a lower voltage were used,   the force produced would be the same. there would not be enough stimulus to produce a contraction. the force produced would be greater. more muscle fibers would be recruited for contraction. the force produced would be lower.

	Human skeletal muscles work to achieve a smooth, steady contraction at all desired levels of force through   (a) stimulus frequency. (b) calcium concentrations. (c) recruitment of motor units. both (a) and (b) both (a) and (c)

	Refer to Activity 6: Investigating Fusion Frequency. The appearance for the multiple stimulus tracings shows that at ________ the force rises and falls.   10 stimuli/sec 20 stimuli/sec 30 stimuli/sec 40 stimuli/sec 50 stimuli/sec

	Refer to Activity 6. When the stimulation rate is changed by 10 stimuli/sec up to 150 stimuli/sec, how do the tracings change?   The active force produced by the muscles stays the same. The active force produced by the muscles decreases. The tracings become smoother. The tracings become more erratic. The force and tracings do not change.

	Refer to Activity 6. The fusion frequency or the tetanus is achieved at ________ stimuli/sec.   100 120 140 160 180

	Refer to Activity 6. At Force = 2 gms, what is the stimulus intensity that produces smooth, sustained force?   100 stimuli/sec and 1.0 volt. 120 stimuli/sec and 1.2 volts. 140 stimuli/sec and 1.4 volts. 160 stimuli/sec and 1.6 volts. 180 stimuli/sec and 1.8 volts.

	Refer to Activity 6. At Force = 3 gms, what is the stimulus intensity that produced smooth, sustained force?   100 stimuli/sec and 1.8 volts. 120 stimuli/sec and 1.6 volts. 140 stimuli/sec and 1.4 volts. 160 stimuli/sec and 1.2 volts. 180 stimuli/sec and 1.0 volts.

	Refer to Activity 6. To achieve smooth contractions at different force levels, what is needed?   (a) An increase in the stimulation rate. (b) A decrease in voltage. (c) An increase in voltage. Both (a) and (b) Both (a) and (c)

	Refer to Activity 7: Investigating Muscle Fatigue. Why does the force decrease with time?   The muscle is in aerobic respiration. ATP is used up faster than it is produced. The voltage is decreased. The stimulus stops. The Krebs cycle shuts down.

	Refer to Activity 8: Investigating Isometric Contraction. What happens to the passive forces as the muscle length is increased from 50 mm to 100 mm?   The passive force remains at zero. The passive force increases sharply. The passive force decreases sharply. The passive force turns into active force. The passive force recruits more motor units.

	Refer to Activity 8. What happens to the active force as the muscle length is increased from 50 mm to 100 mm?   The active force increases steadily until 55 mm and then falls with increasing length. The active force increases steadily until 65 mm and then falls with increasing length. The active force increases steadily until 75 mm and then falls with increasing length. The active force increases steadily until 85 mm and then falls with increasing length. The active force increases steadily until 95 mm and then falls with increasing length.

	Refer to Activity 9: Investigating the Effect of Load on Skeletal Muscle. From the plot results, which of the following is true about the resistance and initial velocity?   As the resistance decreases, the initial velocity of shortening decreases. As the resistance decreases, the initial velocity of shortening increases. As the resistance increases, the initial velocity of shortening decreases. As the resistance increases, the initial velocity of shortening increases. There is no change.

	Can a completely isometric contraction be set up?   Yes No

	Can a completely isotonic contraction be set up?   Yes No

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