Muscle Physiology Lab NAME ______PER _____
Anatomy & Physiology
Note: The same subject must be used for each of the following activities. Each student collects data from the subject. Choose your subject wisely.
Purpose: To investigate differences between isometric and isotonic contractions as well as muscle fatigue and its relationship to oxygen debt, heat and cold.
Part A: Isometric and Isotonic Muscle Contractions
Materials: Tape measure, masking tape.
Your subject is first going to attempt to lift a very heavy object, and then a lighter object. Write a hypothesis below, regarding the length of the muscle change from relaxed to contracted. Your hypothesis should include what you think will happen for both of the sets of contractions.
Hypothesis:
1. Consult the information in your textbook (Table 7-10 on p. 220) showing the location of the origin and insertion of the biceps brachii muscle. Accurately mark these points with masking tape on the subject.
2. Have your subject sit relaxed in a chair and place the fingers of each hand under each side of the seat of the chair, arms and fingers relaxed.
3. Measure with a tape measure the length of the biceps when relaxed, from origin to insertion. Write down this number in the data table below.
4. Now have the subject try to lift up the chair with his or her fingers WHILE STILL SEATED IN THE CHAIR. Tell the subject to “just pull up trying to lift yourself off the floor.” While the muscle is working re-measure the length of the biceps muscle. Record the data on the data table below under “heavy object”.
5. Now have the subject sit relaxed with one with one arm resting on the table or desktop. With the tape measure, measure the length of the biceps muscle and record on the data table below under “light object”.
6. On the palm of the hand, balance an object such as a textbook and have the subject lift by flexing the elbow. Raise the object and again measure the length of the biceps.
7. Compare the muscle lengths for both situations from number 4 and 6. Compare the results to your hypothesis. Explain the data in your formal write-up.
Data Table A:
What is the origin of Biceps?What is the insertion of Biceps?
Length of Biceps Relaxed 1
Length of Biceps Heavy Object
Length of Biceps Relaxed 2
Length of Biceps Light Object
Part B: Demonstration of Muscle Fatigue
Materials: 5-lb weight, stopwatch or clock, blood pressure cuff.
1. Place the subject’s hand palm up on the table with his/her entire hand extending over the edge of the table. Place the 5-lb weight in their hand and allow the wrist to hyperextend as far as possible – relaxing the muscles of the forearm.
2. Count and record the number of full lifts the subject can do over a period of 30 seconds as they raise and lower the weight as quickly as possible using the wrist only. (IMPORTANT: Make sure for each lift the wrist fully flexes and fully hyperextends back to the starting position – don’t cut the movement short). Repeat ten times WITHOUT RESTING BETWEEN TRIALS, and record the data for each 30-second interval in the table below.
3. REST for a few minutes, and then place a blood pressure cuff around the upper arm of the subject. Inflate the cuff until the radial pulse cannot be felt, indicating that the blood supply to the hand has been cut off. WORK QUICKLY AT THIS POINT.
4. Have the subject lift the weight as quickly as possible for THREE 30 second trials without stopping between trials. Record the data for each 30-second interval and immediately loosen and remove the blood pressure cuff.
5. Use graph paper to plot your data from the first and second set of trials recorded in the data table below. Use black for the first set of trials (with oxygen) and gray for the second set (without oxygen). Plot the number of lifts per trial on the vertical (y) axis and the trial number on the horizontal (x) axis. How did the results compare to one another? Include your answer in the conclusion of your formal write-up.
Data Table B:
Trial # (30 seconds)with oxygen / # of lifts / With Blood Pressure Cuff (no oxygen) / # of lifts
1 / 1
2 / 2
3 / 3
4 / STOP
5
6
7
8
9
10
Part C: The Effect of Heat and Cold on Muscle Contractions
Materials: plastic tub, ice water, hot water, clock.
1. You will be repeating the first exercise (number 3) from Part B without the blood pressure cuff after immersing the subject’s forearm in hot water for 2 full minutes. Write your data in the table below.
2. Rest the subject’s arm for a few minutes. Now repeat the procedure after immersing the forearm in ice cold water for 2 full minutes. Record data in the table below.
3. Add to the graph from Part B the new sets of data, using red for the hot water and blue for the cold water. How did the results compare to one another? Include your answer in the conclusion of your formal write-up.
Data Table C:
Trial # / # of lifts “HOT” / # of lifts “COLD”1
2
3
4
5
6
7
8
9
10
Discussion Questions (include the answers in your discussion/conclusion of your formal write up):
1. What is the difference between isometric and isotonic muscle contractions?
2. Explain how the bicep length changed between the relaxed state, lifting the heavy object, and lifting the light object. Why does the biceps muscle change length?
3. How did your results compare for Part B, when your muscles were getting oxygen instead of being deprived of oxygen? Why did you get this result?
4. What happens in your muscles when you work with lack of oxygen?
5. How did your data change from when you exposed the muscle to cold versus hot water? Why do the muscles respond this way?
6. What activities force your muscles to work without the maximum supply of oxygen?