UNIT 3- MUSCLE LAB
The purpose of this lab was to observe the changes in muscle contractions under cold temperature and fatigue. Below I will explain the specific steps I took to observe these conditions, and the muscle's reaction. During contraction of a muscle, the control is made by the Central Nervous System: brain and spinal cord. While studying these chapters and researching, I have learned that during a muscle contraction, the length of the muscle changes, depending on the proteing sliding inside of the muscle fiber. Hopefully this lab will give you a better understanding of what is going on in the muscles while they are contracted, cooled, and fatigued.

The beginning of the procedure was to feel the muscle on your jaw, while clenching down. The brain sent signal for the action potential(communication method from neurons to tissues-muscles and glands) to stimulate the muscle fibers to act. This tightening, I believe is the work of the muscle fibers.

The next step was to measure my upper arm and mark the circumference, while relaxed. Next, I clenched my fist which raised my circumference to a minimal size.

The following steps: Making a tight fist with my hand outstretched 20 times. Result 39 times. Next I submerged my hand in near freezing water for one minute(which was 40 seconds, because it was too cold for me!) I quickly removed my frozen hand and repeated step one. Result 23 times. Therefore, when your extremity is cold it constricts the blood flow, causing my muscles to tense making it harder to clench my fist.

The next steps were to find the effect Fatigue has on muscles. During this exercise I squeezed a tennis ball in my hand 53 times in 20 seconds. I repeated this 9 more times and recorded my results (the graph to the right). Obviously during the repetitious fist clenching, squeezing a tennis ball became tiring and hard after several attempts. When a muscle becomes fatigued, the messages sent down the axon terminal become weak as our muscles tire.

1. What are the 3 changes you observed in a muscle while it is working? First the muscle acts in a strong/fast motion. As it works, the muscle slows down and becomes tired. The weak movements eventually occur when the muscle is worn to its limits.

2. What effect did cold temperature have on the action of your hand muscle? I briefly stated this while talking about the exercise. Submerging an extremity in cold water and then trying to move it, basically constricts the blood flow. This causes the muscle in the hand to tense and move slower than usual. Once the numbness wears off and the constant muscle movement continues; it helps dilate the cells and allow the extremity to move faster/easier.

In conclusion, this exercise shows that increase fatigue and cold wears a muscle down, lowering its ability to function to its fullest. In order for a muscle contraction to occur the 2 proteins, discussed in the review, actin and myosin are released and end up shortening the muscle fibers. The book talks about the release of Ca2+, which causes a contraction. This helps explain when the muscle is cold, contracted, and fatigued the muscle fibers are shorter than usual, taking longer for the energy molecule ATP to form. ATP helps keep the two proteins actin and myosin from binding to each other. At a cellular level, such as the contraction of the muscles, ATP is typically produced for muscle contraction. The amount of exercise or strength a muscle endures causes Ca 2+ to be released, actin and myosin slide around the muscle fiber, and the energy molecule ATP contracts the muscle. The numerous cells inside the muscles work hard during rest and during exercise. This lab proved that muscles become fatigued with lack of oxygen and energy it needs to release the necessary impulses to stay strong.