Muscles Lab Report

Contractility of ASM requires an increased levels of intracellular Ca2+. When surface receptors are not activated, Ca2+ levels are low. Upon activation of these cell surface receptors by contractile agonists e.g. acetylcholine, serotonin and histamine, intracellular Ca2+ increases causing a contraction (9). Smooth muscle cell contraction is controlled by both receptor and mechanical activation of proteins actin and myosin and also changes to membrane potential.

Using electrodes on the bicep to record the motor unit recruitment during all four conditions: control, stretching, cardio, and aerobic stretching. As shown in figure 5, the control group and the stretching are similar in the amount of EMG amplitude (mV). However, when comparing stretching with both cardio and aerobic stretching there is an increase as the intensity of the warm-up. Moreover, aerobic stretching has the highest EMG amplitude, which shows that there is motor unit cycling. Motor cycling provides a more efficient performance on the bicep because more of the muscle is being used (Widmaier, et al.,

Oxygen debt in the muscles is reached when oxygen levels are much lower than required during strenuous physical activity, causing lactate fermentation to occur in the cells leading to muscle fatigue. The results found in the experiment were the number of squeezes in the first trial for the dominant and non-dominant hands were significantly higher than the remaining ones. The results also showed as the trials continued, the number of muscle contractions decreased steadily which supported the hypothesis. However, there were some increased numbers for the dominant hand from trial 4 to 5 and trial 9 to 10. The non-dominant hand expressed similar unexpected results from trial 6 to 7 and trial 9 and 10. The reasons for these results might be due to the finger muscles being worked at the high intensity for a long period of time causing the muscles to consume higher amounts of oxygen thus producing more ATP production. This would cause the muscles to create more contractions towards the end of the trials. The unexpected results could also be caused by experimental errors such as faulty clothespins. The springs connecting the two ends of the clothespin was tight causing the number of contractions as the trials progressed having a more significant decrease. This is because the amount of energy required to open and close the clothespin would be higher, causing the lactate threshold to occur quicker. Due to this, the number of squeezes would decrease drastically as the trials progressed, in contrast to if the springs were normal. This would change the results by the difference between the trials not being evident therefore, not demonstrating the effects of muscle fatigue. Another factor that altered this experiment was the participant’s condition, Palmar Hyperhidrosis –excessive sweating on the palms – which

* Electromyogram- Measures electrical activity of muscles at rest and during contraction. These studies measure how well and fast the nerves can send electrical signals.

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Smooth muscle contraction occurs when calcium is present in the smooth muscle cell and binds onto calmodulin to activate myosin light chain kinase (Wilson et al., 2002). Phosphorylation of myosin light chains result in myosin ATPase activity thus cross-bridge cycling occurs causing the muscle to contract (Horowitz et al., 1996). There are two known models of excitation and contraction in smooth muscle, electromechanical coupling (EMC) and pharmomechanical coupling

Statistics uses math to determine whether or not an experiment happened by chance. In other words, it determines the probability of your results being by chance or if it is factual data. The mathematical ways of determining probably include looking at mean, standard deviation, mode, and median. This experiment will use statistics to test the probability.

Introduction: Exercise is a physical activity or particular movement that is used in order to become healthier and stronger. (1) Exercise, in all of its forms, has various effects on the different systems in the human body. One of the main benefits is cardiovascular health, including circulation and heart health. Exercise uses a lot of energy, which the cells derive from oxidising glucose. Meaning that the heart has to work harder to pump more blood throughout the body and the heart has to beat faster in order to achieve a high effort. (2) The heart benefits from exercise include being able to pump more blood through the body and continue working at a higher level with less strain. (3)

The EMG signal that is observed through the placement of electrodes on the skin is closely coupled with the generation of muscle force. In normal conditions, the force-EMG relationship is either linear or the increase in EMG at low force levels is less than proportional (Semmler 2014). However, a different force-EMG relationship was observed following eccentric exercise,

Every time our body moves, our muscles contract. As the muscle contracts, the muscle becomes fatigued; unable to maintain force output. There are two types of fatigue; central and peripheral (1). Central fatigue involves the central nervous system, whereas peripheral fatigue includes fatigue outside of the central nervous system in the muscles (5). Changes to these systems affect the rate at which the muscle fatigues, including the speed of contraction, the strength of the load, and feedback (5). Therefore, the purpose of this study was to determine whether increased force would influence the time of fatigue, with and without visual feedback. It was hypothesized that as the magnitude of force increased, the time to fatigue would decrease, whereas while the magnitude of force decreased, the time to fatigue would increase. Overall, visual feedback would have increased time to fatigue, compared to non-visual feedback, which would have decreased time to fatigue.

Review Sheet Results 1. Describe how increasing the stimulus frequency affected the force developed by the isolated whole skeletal muscle in this activity. How well did the results compare with your prediction? Your answer: When the stimulus frequency was at the lowest the force was at its lowest level out of all of the experiments. As the stimulus frequency was increased to 130, s/s the force increased slightly but fused tetanus developed at the higher frequency. When the stimulus frequency was increased to the amounts of 146-150 s/s, the force reached a plateau and maximal tetanic tension occurred, where no further increases in force occur from additional stimulus frequency. 2. Indicate what type of force was developed by the isolated skeletal muscle in this activity at the following stimulus frequencies: at 50 stimuli/sec, at 140 stimuli/sec, and above 146 stimuli/sec. Your answer: At 50- Unfused

higher the hertz, the more cycles the sound wave goes through a second. The higher the

To determine the current at which stimulation was maximal, the stimulator was set to 0 Amps and the muscle was stimulated. Then the current was increased by 0.1 Amps and the muscle and force chart were observed. This was repeated until the contraction force stopped increasing, which in this case was at 1.5 Amps. Then the tetanus frequency was determined. First the current was set to 1.5 Amps.

3. How can you explain the increase in force that you observe? the increase is how many volts went into the muscle.

This is because once a contraction has started, the action potential has already fired, stimularing the muscle fibers. Once they