2.1 Skeletal Muscle Physiology
1. Which of the following terms are NOT used interchangeably?
motor unit - motor neuron
2. Which of the following is NOT a phase of a muscle twitch?
shortening phase
3. Where does the acetylcholine that stimulates muscle contraction bind?
receptors in the motor end plate
4. When acetylcholine binds to its receptors, it results in __________.
the end plate potential, a graded depolarization, and a change in ion permeability
5. Which of the following occurs during the latent period of muscle contraction?
Calcium is released from the sarcoplasmic reticulum.
6. As the stimulus voltage was increased in this activity, which of the following occurred?
The muscle force generated increased.
7. Which of the following describes the relaxation phase?
The sarcomeres are increasing in length, and the force generated decreases
8. Which of the following can trigger a muscle twitch?
release of acetylcholine or electrical stimulation
2.2 Skeletal Muscle Physiology
1. Which of the following is proportional to the amount of tension produced by a skeletal muscle?
the number of motor units activated
2. NO force is generated during which of the following?
the latent period
3. What is the minimum voltage needed to generate active force in the skeletal muscle?
threshold voltage
4. A motor unit is defined as _______.
the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates...
5. 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
6. Increasing the applied voltage in the simulation corresponds to which in vivo event?
motor unit recruitment
7. As the stimulus voltage increased, the resulting muscle tension _______.
increased to a point until it reached a plateau
8. Which of the following occurs during the contraction phase?
Cross-bridge cycling is taking place.
2.3 Skeletal Muscle Physiology
1. Treppe is the phenomenon that results in _______.
a progressive increase in the force generated with repetitive stimulation
2. When the frequency of stimulation of a muscle is great enough, _______.
wave summation results and muscle twitches overlap.
3. When wave summation occurs, _______.
the muscle force generated increases
4. Why does wave summation occur?
Muscle fibers are partially contracted when the next stimulus arrives.
5. Which of the following produced an increase in stimulus intensity?
increasing the voltage applied
6. Which of the following produced an increase in stimulus frequency?
clicking the mouse in rapid succession
7. Which of the following does NOT describe treppe?
An increase in stimulus intensity is required to see the effect.
2.4 skeletal muscle physiology
1. Which of the following does NOT describe tetanus?
The muscle relaxes fully between contractions.
2. 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.
3. Muscle twitches overlap with _______.
both fused and unfused tetanus
4. Which of the following would result in fused or unfused tetanus?
increasing the stimulus frequency
5. To transition from unfused tetanus to fused tetanus, _______.
stimulus frequency increase
6. Which of the following describes the relationship between stimulus frequency and muscle tension?
When stimulus frequency increases, muscle tension increases to a maximum value.
7. At what stimulus frequency was maximal tetanic tension developed?
146 stimuli/sec
2.5 Skeletal Muscle Anatomy
1. Which of the following is matched correctly?
complete tetanus - fused tetanus
2. Which of the following situations delay the development of muscle fatigue the longest?
Consistent interruptions of muscle stimulation
3. Which of the following molecules is NOT thought to accumulate during muscle fatigue?
ATP
4. During muscle fatigue, the ____________ decreases.
force of contraction
5. In this activity, why did the muscle force decrease over time?
Muscle fatigue developed
6. Which of the following describes how increasing the duration of the rest period affected muscle tension?
Increasing the duration of the rest period increased the duration of the subsequent maximal tension.
7. What might be occurring on a molecular level during the rest periods?
Intracellular ADP and inorganic phosphate are decreasing.
2.6 Skeletal Muscle Physiology
1. 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.
2. The resting length of the muscle _______.
occurs when the muscle is relaxed
3. 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
4. Which of the following is generated when cross-bridges form between actin and myosin?
active force
5. 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.
6. 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.
7. Which starting length of the muscle provided the maximum total force?
the longest starting length
8. At which muscle length was the passive force the greatest?
100 mm
2.7 Skeletal Muscle Physiology
1. Which of the following occurs during isotonic concentric contraction?
The length of the muscle decreases with contraction.
2. Which of the following occurs during the latent period of isotonic concentric contraction?
.Muscle tension is produced, and the weight will not move.
3. The speed of muscle contraction is called the _______.
shortening velocity
4. For a weight to be lifted, which of the following must occur?
An isotonic muscle contraction with a force greater than the load.
5. When the load to be lifted increases in weight, the latent period _______.
remains unchanged
6. The shortest duration of muscle contraction occurs with _______.
the heaviest load
7. The velocity of shortening _______.
decreased as the weight increased and increased as the weight decreased
8. As the weight increased, the distance the weight was lifted _______.
decreased until the weight was not moved at all
Muscle Lab Review Sheet
1. In Activity 7, which weight resulted in the highest initial velocity of shortening?
0.5g
2. Which of the following statements are correct? (more than one can be correct)
(Both Are Correct)
In vivo, wave summation is achieved by the nervous system increasing firing rate of motor neurons.
In vivo, motor unit recruitment is caused by neural activation of increasingly large numbers of motor units serving the muscle.
3. In Activities 3 and 4, what was the effect of increasing the frequency of stimulation? (choose all that apply)
(Both Are Correct)
The active force generated increased
the force wave becomes smoother
4. Active force decreases until the optimal length is obtained, then increases as muscle length continues to increase beyond optimal length.
False
5. Active force _____________ as muscle length decreases below the optimal length.
Decreases
6. From Activity 2, when voltage was increased, force _______________.
Increased
7. A motor unit consists of a motor neuron and all the muscle cells it innervates.
True
8. When the nerve supply to a muscle is destroyed or badly damaged, the muscle will become flaccid, paralyzed, and eventually atrophy since nerve stimulation is necessary for muscles to remain viable.
True
9. Wave summation is achieved by increasing force of stimulation. Motor unit recruitment is achieved by increasing frequency of stimulation.
False
10. If you were a physical therapist applying a constant voltage to the forearm, what might you observe if you gradually increased the frequency of stimulatory impulses, keeping the voltage constant each time?
You would observe an increase in the duration of forearm muscle contraction.
11. In Activity 1, how long was the latent period? _______ msec (choose the answer closest to the value you measured)
3.20
12. In Activity 3, stimulating the muscle multiple times in a short period with complete relaxation between stimuli causes the force generated to decrease slightly with each subsequent stimulus.
False
13. The maximal response is the level of contraction produced by the maximal stimulus.
True
14. In vivo, increasing force is achieved by neural activation of an increasingly large number of motor units serving the muscle
True
15. Wave summation and motor unit recruitment both cause an increase in active muscle force generated.
True
16. Whole muscle contraction is a graded response.
True
17. When we see the slightest evidence of force production on a tracing, the stimulus applied must have reached tetanus.
False
18. What are the two experimental ways in which mode of stimulation can affect muscle force?
(Both Are Correct)
Stimulus Rate
Stimulus Intensity
19. The weakest stimulation that will elicit the strongest contraction that a muscle is capable of is called the threshold stimulus.
False
20. In Activity 6, at what length (mm) of the muscle does the passive force start to increase?
80
Q 2.1 Muscle Lab Quiz
1. In activity 2, what was the threshold stimulus (voltage)?
0.8
2. Optimum resting length will result in maximum force production.
True
3. You pick up a very light object and hold it at arm's length for several minutes. How is your nervous system accomplishing this?
Frequent Neural Impulses to A Few Motor Units
4. In Activity 7, when the 0.5 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.100
5. When a muscle doesn't have time to relax because of high frequency stimulation
Tetanus
6. What is the correct order of the phases of a muscle twitch?
Latent, Contraction. Relaxation
7. During the latent period, what occurs in the muscle?
Chemical changes occur intracellularly in preparation for contraction
8. In activity 2, what was the maximal stimulus (voltage)?
8.5
9. Increasing the intensity (voltage) of the stimulus going to a muscle
Affects The Strength Of The Contraction
10. Strong muscle contraction implies that many motor units are activated and each unit has maximally contracted.
True
Q 2.2 Muscle Lab Quiz
1. You pick up a very light object and hold it at arm's length for several minutes. How is your nervous system accomplishing this?
Frequent neural impulses to a few motor units
2. Choose all of the following that are correct about the oscilloscope display in the computer simulation.
(Both Are Correct)
time (msec) was displayed on the horizontal axis
force (in grams) produced by muscle contraction was displayed on the vertical axis
3. Muscle fatigue results when all of the muscle cell'sATP is consumed.
False
4. In Activity 7, when the 1.0 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.057
5. When a muscle doesn't have time to relax because of high frequency stimulation
Tetanus
6. In Activity 7, when the 2.0 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.00
7. In Activity 7, isotonic contraction was tested by keeping both ends of the muscle in a fixed position.
False
8. In activity 2, what was the threshold stimulus (voltage)?
0.8
9. You begin stimulating a muscle at 1.0 V and increase the voltage by 0.2 V up to 6.0 V in an attempt to elicit a response. According to the data collected, the muscle first generates active force at 1.8 V and no significant difference in the active force generated is seen after 4.6 V. Based on this experiment, what is the minimal (threshold) stimulus for this muscle?
1.8 V
10. In activity 1, the latent period was approximately _______ msec.
3.2
1. Which of the following terms are NOT used interchangeably?
motor unit - motor neuron
2. Which of the following is NOT a phase of a muscle twitch?
shortening phase
3. Where does the acetylcholine that stimulates muscle contraction bind?
receptors in the motor end plate
4. When acetylcholine binds to its receptors, it results in __________.
the end plate potential, a graded depolarization, and a change in ion permeability
5. Which of the following occurs during the latent period of muscle contraction?
Calcium is released from the sarcoplasmic reticulum.
6. As the stimulus voltage was increased in this activity, which of the following occurred?
The muscle force generated increased.
7. Which of the following describes the relaxation phase?
The sarcomeres are increasing in length, and the force generated decreases
8. Which of the following can trigger a muscle twitch?
release of acetylcholine or electrical stimulation
2.2 Skeletal Muscle Physiology
1. Which of the following is proportional to the amount of tension produced by a skeletal muscle?
the number of motor units activated
2. NO force is generated during which of the following?
the latent period
3. What is the minimum voltage needed to generate active force in the skeletal muscle?
threshold voltage
4. A motor unit is defined as _______.
the axon terminals of a single motor neuron and all of the muscle fibers that it stimulates...
5. 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
6. Increasing the applied voltage in the simulation corresponds to which in vivo event?
motor unit recruitment
7. As the stimulus voltage increased, the resulting muscle tension _______.
increased to a point until it reached a plateau
8. Which of the following occurs during the contraction phase?
Cross-bridge cycling is taking place.
2.3 Skeletal Muscle Physiology
1. Treppe is the phenomenon that results in _______.
a progressive increase in the force generated with repetitive stimulation
2. When the frequency of stimulation of a muscle is great enough, _______.
wave summation results and muscle twitches overlap.
3. When wave summation occurs, _______.
the muscle force generated increases
4. Why does wave summation occur?
Muscle fibers are partially contracted when the next stimulus arrives.
5. Which of the following produced an increase in stimulus intensity?
increasing the voltage applied
6. Which of the following produced an increase in stimulus frequency?
clicking the mouse in rapid succession
7. Which of the following does NOT describe treppe?
An increase in stimulus intensity is required to see the effect.
2.4 skeletal muscle physiology
1. Which of the following does NOT describe tetanus?
The muscle relaxes fully between contractions.
2. 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.
3. Muscle twitches overlap with _______.
both fused and unfused tetanus
4. Which of the following would result in fused or unfused tetanus?
increasing the stimulus frequency
5. To transition from unfused tetanus to fused tetanus, _______.
stimulus frequency increase
6. Which of the following describes the relationship between stimulus frequency and muscle tension?
When stimulus frequency increases, muscle tension increases to a maximum value.
7. At what stimulus frequency was maximal tetanic tension developed?
146 stimuli/sec
2.5 Skeletal Muscle Anatomy
1. Which of the following is matched correctly?
complete tetanus - fused tetanus
2. Which of the following situations delay the development of muscle fatigue the longest?
Consistent interruptions of muscle stimulation
3. Which of the following molecules is NOT thought to accumulate during muscle fatigue?
ATP
4. During muscle fatigue, the ____________ decreases.
force of contraction
5. In this activity, why did the muscle force decrease over time?
Muscle fatigue developed
6. Which of the following describes how increasing the duration of the rest period affected muscle tension?
Increasing the duration of the rest period increased the duration of the subsequent maximal tension.
7. What might be occurring on a molecular level during the rest periods?
Intracellular ADP and inorganic phosphate are decreasing.
2.6 Skeletal Muscle Physiology
1. 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.
2. The resting length of the muscle _______.
occurs when the muscle is relaxed
3. 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
4. Which of the following is generated when cross-bridges form between actin and myosin?
active force
5. 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.
6. 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.
7. Which starting length of the muscle provided the maximum total force?
the longest starting length
8. At which muscle length was the passive force the greatest?
100 mm
2.7 Skeletal Muscle Physiology
1. Which of the following occurs during isotonic concentric contraction?
The length of the muscle decreases with contraction.
2. Which of the following occurs during the latent period of isotonic concentric contraction?
.Muscle tension is produced, and the weight will not move.
3. The speed of muscle contraction is called the _______.
shortening velocity
4. For a weight to be lifted, which of the following must occur?
An isotonic muscle contraction with a force greater than the load.
5. When the load to be lifted increases in weight, the latent period _______.
remains unchanged
6. The shortest duration of muscle contraction occurs with _______.
the heaviest load
7. The velocity of shortening _______.
decreased as the weight increased and increased as the weight decreased
8. As the weight increased, the distance the weight was lifted _______.
decreased until the weight was not moved at all
Muscle Lab Review Sheet
1. In Activity 7, which weight resulted in the highest initial velocity of shortening?
0.5g
2. Which of the following statements are correct? (more than one can be correct)
(Both Are Correct)
In vivo, wave summation is achieved by the nervous system increasing firing rate of motor neurons.
In vivo, motor unit recruitment is caused by neural activation of increasingly large numbers of motor units serving the muscle.
3. In Activities 3 and 4, what was the effect of increasing the frequency of stimulation? (choose all that apply)
(Both Are Correct)
The active force generated increased
the force wave becomes smoother
4. Active force decreases until the optimal length is obtained, then increases as muscle length continues to increase beyond optimal length.
False
5. Active force _____________ as muscle length decreases below the optimal length.
Decreases
6. From Activity 2, when voltage was increased, force _______________.
Increased
7. A motor unit consists of a motor neuron and all the muscle cells it innervates.
True
8. When the nerve supply to a muscle is destroyed or badly damaged, the muscle will become flaccid, paralyzed, and eventually atrophy since nerve stimulation is necessary for muscles to remain viable.
True
9. Wave summation is achieved by increasing force of stimulation. Motor unit recruitment is achieved by increasing frequency of stimulation.
False
10. If you were a physical therapist applying a constant voltage to the forearm, what might you observe if you gradually increased the frequency of stimulatory impulses, keeping the voltage constant each time?
You would observe an increase in the duration of forearm muscle contraction.
11. In Activity 1, how long was the latent period? _______ msec (choose the answer closest to the value you measured)
3.20
12. In Activity 3, stimulating the muscle multiple times in a short period with complete relaxation between stimuli causes the force generated to decrease slightly with each subsequent stimulus.
False
13. The maximal response is the level of contraction produced by the maximal stimulus.
True
14. In vivo, increasing force is achieved by neural activation of an increasingly large number of motor units serving the muscle
True
15. Wave summation and motor unit recruitment both cause an increase in active muscle force generated.
True
16. Whole muscle contraction is a graded response.
True
17. When we see the slightest evidence of force production on a tracing, the stimulus applied must have reached tetanus.
False
18. What are the two experimental ways in which mode of stimulation can affect muscle force?
(Both Are Correct)
Stimulus Rate
Stimulus Intensity
19. The weakest stimulation that will elicit the strongest contraction that a muscle is capable of is called the threshold stimulus.
False
20. In Activity 6, at what length (mm) of the muscle does the passive force start to increase?
80
Q 2.1 Muscle Lab Quiz
1. In activity 2, what was the threshold stimulus (voltage)?
0.8
2. Optimum resting length will result in maximum force production.
True
3. You pick up a very light object and hold it at arm's length for several minutes. How is your nervous system accomplishing this?
Frequent Neural Impulses to A Few Motor Units
4. In Activity 7, when the 0.5 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.100
5. When a muscle doesn't have time to relax because of high frequency stimulation
Tetanus
6. What is the correct order of the phases of a muscle twitch?
Latent, Contraction. Relaxation
7. During the latent period, what occurs in the muscle?
Chemical changes occur intracellularly in preparation for contraction
8. In activity 2, what was the maximal stimulus (voltage)?
8.5
9. Increasing the intensity (voltage) of the stimulus going to a muscle
Affects The Strength Of The Contraction
10. Strong muscle contraction implies that many motor units are activated and each unit has maximally contracted.
True
Q 2.2 Muscle Lab Quiz
1. You pick up a very light object and hold it at arm's length for several minutes. How is your nervous system accomplishing this?
Frequent neural impulses to a few motor units
2. Choose all of the following that are correct about the oscilloscope display in the computer simulation.
(Both Are Correct)
time (msec) was displayed on the horizontal axis
force (in grams) produced by muscle contraction was displayed on the vertical axis
3. Muscle fatigue results when all of the muscle cell'sATP is consumed.
False
4. In Activity 7, when the 1.0 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.057
5. When a muscle doesn't have time to relax because of high frequency stimulation
Tetanus
6. In Activity 7, when the 2.0 g weight was attached to the muscle, what was the initial velocity of shortening (cm/sec)?
0.00
7. In Activity 7, isotonic contraction was tested by keeping both ends of the muscle in a fixed position.
False
8. In activity 2, what was the threshold stimulus (voltage)?
0.8
9. You begin stimulating a muscle at 1.0 V and increase the voltage by 0.2 V up to 6.0 V in an attempt to elicit a response. According to the data collected, the muscle first generates active force at 1.8 V and no significant difference in the active force generated is seen after 4.6 V. Based on this experiment, what is the minimal (threshold) stimulus for this muscle?
1.8 V
10. In activity 1, the latent period was approximately _______ msec.
3.2