1. As you increase voltage to the muscle describe how it responds to the increased stimulus. As the voltage was increased from threshold to maximum voltage, there was a greater force in the muscle contraction. Once the maximum voltage (2500 mv) was reached, even if there was an increase in voltage, the force of the muscle contraction remained the same. 2. What was the smallest voltage required to produce a contraction (the threshold voltage)? What proportion of the fibers in the muscle do you think were contracting to produce this small response? 0.2500V , a small contraction of all the muscle fibers 3. What was the smallest voltage required to produce the maximum (largest) contraction? What proportion of the fibers in the …show more content…
Increases in force as it stretches. 7. What effect does stretching the muscle have on contraction strength? Is this effect linear? The further the muscle is stretched the bigger the force it exerts. This is a linear effect. 8. What stretch resulted in the highest contraction force? What happens to the muscle at the highest stretch levels? The 10mm stretch. It contracts more vigorously. 9. Describe how the isolated muscle behaved as the stimulus interval was decreased progressively. As the intervals were reduced the twitches got closer together. Each curve, which represents a response to the stimuli, got closer until they finally became one. This represents summation which is when the muscle is unable to completely relax before the next stimulus occurs. As a result, individual twitches begin to combine, and the contraction becomes sustained. 10. How does varying the frequency effect contraction force? Which interval caused the greatest contraction? The shorter the intervals the greater the force. The 20ms interval causes the greatest force. 11. Describe how the isolated muscle behaved as the stimulus interval was further decreased. As the intervals were reduced the twitches got closer together. Each curve, which represents a response to the stimuli, got closer until they finally became one. This represents summation which is when the muscle is unable to completely relax before
The more stimuli per second, the greater the force generated by the muscle due to a
This activity is the critical driving force of muscle contraction. The stream of action potentials along the muscle fiber surface is terminated as Acetylcholine at the neuromuscular junction is broken down by acetyl cholinesterase. The release of Calcium ions is ceased. The action of the myosin molecule heads is obstructed because of the change in the configuration of troponin and tropomyosin due to the absence of calcium ions. This will eventually cause the contraction to be ceased. Together with these physical processes, an external stretching force such as gravity pulls the muscle back to its normal length.
3. Considering your answers to Questions 1 and 2, why did activity in Annie’s motor nerves produce a skeletal muscle response that fatigued during repetitive stimulation?
1. Predict if healthy muscle or muscle with MH will contract with the most force.
contraction, and this reduction in tension production is the cause of the loss of strength. Her muscles are actually
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
As a result of the contractions in the Muscle- Skeletal Longitudinal Section cells and the Muscle- Skeletal Cross Section cells, it allows your muscle to be able to contract in response to nerve stimuli. This means that the movements of most of these muscles are not involuntary, you can control them. Therefore, once the stimulation stops, the muscles relax.
Next with a stimulation duration of 50us, the stimulus amplitude should be set to the maximal tolerable stimulus intensity. With stimulus frequency of 2Hz, observe and record the leg movement, increase it by 5Hz but should not exceed 50Hz. With the electrodes connected to the analogy output channel and ground of the DAQ board. With the corresponding LabVIEW program, the frequency and amplitude (voltage) of the stimulation supplied to the leg can be controlled. With this the “sweet spot” of the lowest amplitude and best frequency to cause evoked movement can be found and recorded. Now the stimulation frequency should be set to 10Hz and the duration of stimulation pulse to 5ms or less. The range if leg movement changes can be observed as amplitude changes. Electrical stimulation in increments of 0.01V should be delivered and the minimal voltage required to generate muscle twitch should be recorded. The pulse duration should then be increased by durations of 10ms and the minimum voltage should be recorded this should be repeated for a variety of pulse
In this exercise, you examined the effect of increasing stimulus intensity on the nerve. What other stimulus parameter
1. How is there a lower metabolic cost but with the higher forces during eccentric contraction?
3. Perform ten resistance training exercises and describe which phase of the exercise is the eccentric, concentric and isometric phase of the movement. At which phase is the muscle the strongest? Why?
5. What effect did temperature have on muscle contraction? Do some outside Internet research (cite your sources) and explain.
9. Strong involuntary muscle reactions to shocks can occur in a amperage ranges as low as __________________.
Hence, this would allow for an influx of sodium into the cell down its electrochemical gradient. It would also allow for the flow of potassium outward, as it has a 140mM concentration inside the cell and wants to shift down its concentration gradient to 5.4mM. Therefore, this great driving force for the influx of sodium and efflux of potassium helps to explain the findings at this point. As Table 1 shows, the findings within this figure are statistically supported. The fact that there is not significant difference between the findings of this experiment and the calculated Nernst at the 10, 20 and 40mM of potassium is an indicator that sodium is the largest determinant of the resting membrane potential. However, some findings defy the expectations, as the last two concentrations elicit a resting membrane potential significantly more negative than expected. This can be explained by the fact that at this point, each muscle at their respective muscle groups has been protruded many
3. How can you explain the increase in force that you observe? the increase is how many volts went into the muscle.