Contracting Muscle
Rubber Ball
Submerging my Hand in Icewater
Muscle Contraction Cycle http://people.emich.edu/pbogle/PHED_200/outlines/chapter_08/outline.htm
Mechanism of Muscle Contraction
http://courses.cm.utexas.edu/jrobertus/ch339k/overheads-1.htm)
Muscle Function Lab
Introduction: This lab is designed to show a person how his / her muscles react to environmental changes, such as temperature, and fatigue. It is important to understand the basic function of our muscles for many reasons, including understanding how to exercise effectively, and how our bodies and muscles react to environmental changes. Here, we will test how our muscles contract normally, and how these contractions change when introduced to other circumstances, such as fatigue from overuse and drastic temperature changes.
1. Muscle Action: Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and observe what happens to the hardness of the
muscles in your cheek.
They become hard.
2. With the thumb and little finger of one hand, span the opposite arm's
biceps (front muscle of the upper arm) from the elbow to as close to the
shoulder as possible. Bend the arm and observe the change in the length of
the muscle. It shortens / contracts.
3. Wrap a strip of paper around your upper arm and mark the circumference
of your arm on the paper. Clench your fist tightly and mark the new
circumference on the paper. Observe what happens to the circumference of
the muscle. Increases.
Effect of Temperature on Muscle Action
1. Count the number of times you can make a fist in 20 seconds. Start with
your hand completely outstretched and make a tight fist each time. Do it
as rapidly as you can. Record the count: 24.
2. Now submerge your hand in a dishpan of water to which has been added
snow or ice so that the temperature is near the freezing point. Leave your
hand in the water for one full minute.
3. Remove your hand and immediately count how many forceful fists you can
make in 20 seconds. Record in Figure 1.
Number of Fists “Normal”: 24
Number of Fists “Ice Water”: 20
4. Effect of Fatigue on Muscle Action
1. Count how many times you can tightly squeeze a rubber ball in your hand
in 20 seconds. Record figure: 45
2. Repeat the squeezing nine more times and record results. Do not rest
between trials.
Number of rubber ball squeezes in 20 seconds / 10 Repetitions
1st: 45
2nd: 45
3rd: 44
4th: 43
5th: 44
6th: 44
7th: 41
8th: 41
9th: 40
10th: 39
ANALYSIS OF DATA:
1. What are the three changes you observed in a muscle while it is working (contracted)?
A. When you flex a muscle, it becomes larger and / or harder.
B. Your body temperature directly affects the ability of the muscle to perform: when the muscle is submerged in ice water, (and you get over the physical pain), :) the muscle is unable to perform as efficiently and as much as it could at normal temperature.
C. When you use a muscle repeatedly in a period of time, it becomes fatigued, and is unable to perform as efficiently and as much as it could at rest.
2. What effect did the cold temperature have on the action of your hand muscles? Explain.
- First, I was very surprised at the amount of pain that was involved in holding my hand in ice water for a full minute. I kept wanting to take it out of the water! But I held it in, and I felt the “pins and needles” pain go up my arm! (Sensory neurons!) :) After I took it out and repeated the exercise of fist clenching, I found that it was much more difficult to make the fist than it was before, and it occurred at a much slower rate. (I was only able to make 20 fists as opposed to 24) 3. (Graph)
4. What effect did fatigue have on the action of your hand muscles? Explain. Fatigue makes your muscles tired. A tired muscle cannot perform as well or do as many repetitions as it can when it is rested. The first time I squeezed the ball in 20 seconds, when my muscle was rested, I squeezed it 45 times. That number gradually dropped as I continued the repetitions. By the tenth repetition, I could only squeeze it 39 times.
* Conclusion:
Muscles contract and break down ATP for the energy they need. When this happens, heat is released throughout the body. When you submerge your hand in ice water, it becomes harder to contract your muscles. This must mean that ATP does not break down well in a cold environment, so it is harder to contract your muscles, and therefore harder to spread heat throughout your body. Muscle contractions keep blood moving, so when you contract them less, there is less blood flow, also making it harder to contract the muscle.
Muscle Function Lab
Introduction: This lab is designed to show a person how his / her muscles react to environmental changes, such as temperature, and fatigue. It is important to understand the basic function of our muscles for many reasons, including understanding how to exercise effectively, and how our bodies and muscles react to environmental changes. Here, we will test how our muscles contract normally, and how these contractions change when introduced to other circumstances, such as fatigue from overuse and drastic temperature changes.
1. Muscle Action: Place your fingers along the angle of your jaw just in front of your ear. Grit your teeth and observe what happens to the hardness of the
muscles in your cheek.
They become hard.
2. With the thumb and little finger of one hand, span the opposite arm's
biceps (front muscle of the upper arm) from the elbow to as close to the
shoulder as possible. Bend the arm and observe the change in the length of
the muscle. It shortens / contracts.
3. Wrap a strip of paper around your upper arm and mark the circumference
of your arm on the paper. Clench your fist tightly and mark the new
circumference on the paper. Observe what happens to the circumference of
the muscle. Increases.
Effect of Temperature on Muscle Action
1. Count the number of times you can make a fist in 20 seconds. Start with
your hand completely outstretched and make a tight fist each time. Do it
as rapidly as you can. Record the count: 24.
2. Now submerge your hand in a dishpan of water to which has been added
snow or ice so that the temperature is near the freezing point. Leave your
hand in the water for one full minute.
3. Remove your hand and immediately count how many forceful fists you can
make in 20 seconds. Record in Figure 1.
Number of Fists “Normal”: 24
Number of Fists “Ice Water”: 20
4. Effect of Fatigue on Muscle Action
1. Count how many times you can tightly squeeze a rubber ball in your hand
in 20 seconds. Record figure: 45
2. Repeat the squeezing nine more times and record results. Do not rest
between trials.
Number of rubber ball squeezes in 20 seconds / 10 Repetitions
1st: 45
2nd: 45
3rd: 44
4th: 43
5th: 44
6th: 44
7th: 41
8th: 41
9th: 40
10th: 39
ANALYSIS OF DATA:
1. What are the three changes you observed in a muscle while it is working (contracted)?
A. When you flex a muscle, it becomes larger and / or harder.
B. Your body temperature directly affects the ability of the muscle to perform: when the muscle is submerged in ice water, (and you get over the physical pain), :) the muscle is unable to perform as efficiently and as much as it could at normal temperature.
C. When you use a muscle repeatedly in a period of time, it becomes fatigued, and is unable to perform as efficiently and as much as it could at rest.
2. What effect did the cold temperature have on the action of your hand muscles? Explain.
- First, I was very surprised at the amount of pain that was involved in holding my hand in ice water for a full minute. I kept wanting to take it out of the water! But I held it in, and I felt the “pins and needles” pain go up my arm! (Sensory neurons!) :) After I took it out and repeated the exercise of fist clenching, I found that it was much more difficult to make the fist than it was before, and it occurred at a much slower rate. (I was only able to make 20 fists as opposed to 24) 3. (Graph)
4. What effect did fatigue have on the action of your hand muscles? Explain. Fatigue makes your muscles tired. A tired muscle cannot perform as well or do as many repetitions as it can when it is rested. The first time I squeezed the ball in 20 seconds, when my muscle was rested, I squeezed it 45 times. That number gradually dropped as I continued the repetitions. By the tenth repetition, I could only squeeze it 39 times.
* Conclusion:
Muscles contract and break down ATP for the energy they need. When this happens, heat is released throughout the body. When you submerge your hand in ice water, it becomes harder to contract your muscles. This must mean that ATP does not break down well in a cold environment, so it is harder to contract your muscles, and therefore harder to spread heat throughout your body. Muscle contractions keep blood moving, so when you contract them less, there is less blood flow, also making it harder to contract the muscle.
When the nervous system stimulates a muscle, sarcolemma (the cell's plasma membrane) forms T tubules that penetrate, or dip down into, the cell so that they come into contact but do not fuse with expanded portions of the sarcoplasmic reticulum. These expanded portions of the sarcoplasmic reticulum are calcium storage sites, and calcium is essential for muscle contraction, so it is released from the sarcoplasmic reticulum. Myofibrils, found in the sarcoplasmic reticulum are the contractile portions of the muscle fibers. Motor neurons stimulate the muscle fibers to contract, as the sarcomeres in the myofibrils shorten. Muscle relaxes when Ca2+ returns to sarcoplasmic reticulum. During the 10 repetitions of squeezing the ball, we were specifically told not to rest between the repetitions, so calcium did not have a chance to return to the sarcoplasmic reticulum. Therefore, the amount of calcium that is released becomes less because you are using it faster than it is being replenished. It seems that when you repeat this process several times, the muscle slows down. Perhaps the motor nuerons cannot act as quickly so the impulse travels more slowly. When submerged in ice water, perhaps the actin-myosin units (sarcomeres) take longer to shorten, and therefore longer to contract.
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