Biology

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Muscle Physiology Lab Assignment

Part I: Muscle Twitch

The latent period is the time from the initial stimulation to the start of the muscle contraction. The

delay occurs as the neurotransmitter delivers the action potential and engages the myofilaments

(actin and myosin) in the muscle fiber. The contraction phase involves the shortening of the fiber

and the creation of tension or force within the muscle. The myosin pulls on the actin to shorten the

fiber. See Figure 3. The relaxation phase occurs when the neurotransmitter is broken down and the

actin and myosin go back to their resting positions. This decreases the tension and force in the

muscle. Muscle twitches can be measured and recorded. The information can be presented in a

graph called a myogram. Myograms graphically show the relationships between different kinds of

muscle contractions and the force they create in a variety of muscles. Study the data for the three

muscles in Tables 1A, 1B, and 1C.

Data Table 1A: Muscle twitch of the lateral rectus eye muscle

Time (milliseconds)

Tension (kilogram-force)

0 0

1 0

2 0

3 10

4 20

5 30

6 40

7 30

8 20

9 10

10 5

11 2

12 0

Data Table 1B: Muscle twitch of the rectus femoris muscle

Time (milliseconds)

Tension (kilogram-force)

Time (milliseconds)

Tension (kilogram- force)

0 0 21 30

3 10 24 25

6 20 27 22

9 30 30 15

12 35 33 12

15 40 36 5

2

18 45 39 0

Data Table 1C: Muscle twitch of the plantaris

Time (milliseconds) Tension (kilogram-force)

0 0

5 5

10 15

15 20

20 25

25 30

30 32

35 36

40 40

45 38

50 35

55 32

60 25

65 22

70 18

75 15

80 12

85 10

90 5

95 3

100 0

1. Make a scatter plot graph in Microsoft Excel® using Data Tables 1A, 1B, and 1C that show

the twitch tension timelines of the eye, rectus femoris, and plantaris muscle fibers. For each

muscle, connect the dots together in sequence.

Graph all three sets of data on one graph. Label the three muscles on the graph.

(3 points)

2. Graph the rectus femoris muscle. Label the latent period, contraction phase and relaxation phase.

(2 points)

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Part II: Muscle Fatigue

In this exercise, muscle fatigue will be demonstrated by lifting a heavy object. A partner or family

member may be required to assist with this exercise.

1. Before beginning, set up a data table similar to the Data Table 5 in the Lab Report Assistant section

to record observations while performing the experiment.

2. Use a stopwatch.

3. Retrieve the Anatomy and Physiology textbook (or other heavy textbook).

4. Record a zero “0” in the start time column for Trial 1 into Data Table 5.

5. Stand up and extend an arm straight out in front of you (DO NOT BEND YOUR ELBOW AT ALL) so

that the arm is parallel to the floor.

6. Hold your hand out with your palm flat and fingers straight. Place your A&P text in your hand and

immediately start the stopwatch.

7. Hold the book straight out in front of you until the arm starts to ache or burn. Ask the partner to

record this time into Data Table 5 as “Aching/Burning Feeling Begins.”

8. When the arm begins to drop, ask the partner to record the final time as “Arm Begins to Drop

(seconds).”

9. Put down the book and begin the rest period. Rest for one minute.

10. Repeat Steps 4 through 9 twice more, for a total of three trials. Record the data for Trials 2 and 3

next to “2” and “3” in Data Table 5, respectively.

11. Calculate the total time in seconds required for each trial and record this under “Duration” in Data

Table 5.

Plot a graph for the total time it took for fatigue to set in for each trial. Label the horizontal axis as

“Trial” and the vertical axis as “Time in Seconds.” (2 points)

Data Table 5: Muscle Fatigue

Trial Start Time (seconds)

Aching/Burning Feeling Begins (seconds)

Arm Begins to Drop (seconds)

Duration (seconds)

1

2

3

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Part III: Isometric and Isotonic Contractions

In this activity, both isometric and isotonic contractions will be demonstrated. You may need a

partner or family member to help you with this exercise.

1. Before beginning, set up a data table similar to the Data Table 6 to record observations while

performing the experiment.

2. Retrieve a textbook or other heavy textbook.

3. Obtain the ruler with metric measurements.

4. Stand up and extend your arm straight out in front of you so that it is parallel to the floor. Do NOT

BEND YOUR ELBOW AT ALL.

5. Palpate (feel) your biceps brachii muscle. Feel the tension of the muscle and measure the length

using the ruler. Record this information into Data Table 6, “Trial 1”

6. Hold your hand out and load your arm with the textbook. Palpate the biceps brachii again and

notice the degree of muscle tension. Measure the length of the muscle. Record your observations

under “Trial 2” in Data Table 6.

7. Gently squeeze the biceps brachii muscle with your opposite hand. Repeatedly flex your arm

holding the book six times. Move the textbook at least six inches each time. Palpate the muscle

while doing the repetitions, and hold the book at the top of the repetition to measure length again

with the ruler. Record your muscle tension and length observations under “Trial 3” in Data Table 6.

Fill in the “Type of Contraction” for each trial in Data Table 6. (3 points)

Data Table 6: Isometric and Isotonic Contractions

Trial 1 Trial 2 Trial 3

Tension

Length

Type of Contraction