October 2, 2012
Skeletal Muscle physiology exercise
name each phase of a typical muscle twitch and on the following line. Describe what is happening in each phase. a) latent- is a short period between the time of stimulation and the beginning of contraction b). Contraction – at this stage the muscle reaches its peak in contraction. Relaxation -Muscle is shortened, returns to zero and back initial length.
In activity 2 how long was the latent period? It was 2.2 msec. Describe the chemical changes that are occurring during this period. Calcium levels are low since muscle contraction is not at its peak. Preparing on the contraction Ca begin the process of sending Acetylcholine binding to sarcoplasm.
The Graded Muscle Response to Increased Stimulus Intensity
From activity 3, describe the effect of increasing the voltage. What happened to the force generated and why did this change occur? Higher voltage results in higher force and a higher contractile force. How does this change occur in vivo? T the more stimulus of muscle require more work on the cells which required more Ca2t to facilitate this stimulus increase. In activity 4, you looked at the effect of stimulating the muscle times in a short period with complete relaxation between the stimuli. Describe the force of contraction with each subsequent stimulus. Answer: The force of contraction is higher with each subsequent stimulus.
Describe the chemical changes that are thought to correlate to this change in vivo. Answer: This requires more Ca t2 in the sarcoplasm and more activity on the thin filament for cross-bridge attachments.
In activity 5, what was the effect of increasing the frequency of stimulation. Answer: Increase frequency of stimuli result in increased muscle tension
Compare and contrast wave summation with recruitment ( multiple motor unit summation). How are they similar? How was each achieved in the stimulation? Answers to both questions are this. Muscles are stimulated to contract by electrical signals usually from the brain. These waves of
electricity can be piled on top of each other, causing increased strength and duration of muscle contraction. Motor recruitment involves sending signals to multiple parts of the muscle at once, resulting in one quick, strong contraction. Summation is similar in that it increase contractile force.
Explain how wave summation and recruitment are achieved in vivo? Answer: In order for a muscle to contract electrical shock or nerve impulse must cause voltage-sensitive tubule proteins (T-tubules) of sarcoplasmic reticulum to change shape and allow Ca2t into cytosol. Ca2t binds to troponin ( changing its shape) allowing myosin ( make thick filaments) to attach to actin ( makes thin filaments). Myosin pulls itself along actin via ATP hydrolysis, this called a cross-bridge cycle, basically shortening of muscle. Before the contraction stops, another stimulus is sent to the muscle allowing more Ca2t into the cytosol which keeps allowing cross-bridge cycle wave summation. Means the contractions are added together, thus increasing the force of the second stimuli force will increase until the muscle reaches it threshold.
In activity 6, explain how you were able to achieve smooth contraction at a given force level. Answer: Smooth contraction at a given force level are obtain by increasing the force of stimulation for a high force level or decreasing the force of stimulation for a low level.
In activity 7, explain why the the force muscle decreased over time during uninterrupted stimulation. Describe the multiple causes of the phenomenon which occurs in vivo with prolonged use of muscle. Answer: ATP consumption is greater than its production, lactic acid build-up then causes pH to decrease which results in enzyme activity and this is why...