The acetylcholine binds with receptors on the muscle membrane which are in close proximity to the neuron (the motor end plate). The binding of the acetylcholine to the muscle membrane allows for the initiation of an action potential (which promotes the passing of an electrical current) on the muscle membrane. A special enzyme, acetylcholinesterase, breaks down the released acetylcholine so that it cannot continue to bind to the muscle membrane. In this way, the nerve controls the action of the muscle such that the muscle can only generate a current when the nerve has first generated a current. )Describe the process of excitation-contraction coupling in skeletal muscle fibers. AP propagates along sarc olemma and down T- tubule Release of Ca2 from SR into sarcoplasm Ca2 binds to troponin which removes tropomyosin from actin binding sites Contraction begins Calcium influx Ca binds to Troponin, actin site exposed Myosin binds to actin Cross bridge/powerstroke
The period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle cell and the start of muscle contraction. Although no force is generated during the latent period, chemical changes (including the release of calcium from the sarcoplasmic reticulum) occur interacellularly in preparation for contraction. Contraction The amount of time that starts at the end of the latent period and ends when muscle tension peaks. Relaxation phase Is the period of time from peak tension until the end of the muscle contraction. )Does the duration of the latent period change with different stimulus voltages? How well did the results compare with your prediction? No it does not… we originally guess that it would change, but were wrong. 6)At the threshold stimulus, do sodium ions start to move into or out of the cell to bring about depolarization? Into the cell Activity 2: The Effect of Stimulus Voltage on Skeletal Muscle Contraction Describe the effect of increasing stimulus voltage on isolated skeletal muscle. Specifically, what happened to the muscle force with stronger electrical stimulations and why did this change occur?
How well did the results compare with your prediction? As the stimulus increased the muscle tension also increased but not in proportion. The threshold voltage was 0. 8 and it yielded a significant increase in muscle tension but as the stimuli continued the muscle force increased in smaller and smaller amounts until it reached a plateau when all the motor units available were activated. 1)How is this change in whole-muscle force achieved in vivo? 2)What happened in the isolated skeletal muscle when the maximal voltage was applied? Activity 3: The Effect of Stimulus Frequency on Skeletal Muscle Contraction