Skeletal Muscle Lab

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Skeletal Muscle Lab

Introduction: Motor neurons and muscle fibers are the building blocks of motor units and where they intersect is called the neuromuscular junciton. The region where the flattened end of a motor neuron transmits neural impulses to a muscle is the motor end-plate. The end plate potentials depolarizes skeletal muscle fibers caused by neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction. The process of contraction of the muscle cell is called excitation-contraction coupling. In this experiment, when we used a single electrical stimulus, it resulted in a muscle twitch with three phases: latent period, contraction phase, and the relaxation phase.

Activity 1: Figure 1: Identifying the latent period

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The Latent Period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle contraction. The length of the latent period was 2.78msec. When we increased the stimulus voltage from 3v to 9v and then to 10v, the latent period remained the same at 2.78msec. Thus, the latent period does not change with different stimulus.

Activity 2: Figure 2: Identifying the Threshold Voltage

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The threshold is the minimal stimulus needed to cause a depolarization of the muscle plasma membrane. It is the point at which sodium ions start to move into the cell for membrane depolarization. When we stimulated the voltage of 0, the active force showed a straight line such as depicted in figure 2. We kept on increasing the threshold hold voltage until it showed a value greater than 0. The threshold voltage value was .8v to have the active force be greater than 0. The graph generated at the threshold differed from the graphs generated at voltages below the threshold because the active force was greater than 0 at .8v compared to 0v.

Activity 3: Figure 3: Effect of increasing the stimulus intensity

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|Table 1: Activity 3 | | | | | | | | | | |Voltage |Length |Active Force |Passive Force |Total Force | |0.5 |75 |0 |0 |0 | |1 |75 |0.15 |0 |0.15 | |1.5 |75 |0.43 |0 |0.43 | |2 |75 |0.66 |0 |0.66 | |2.5 |75 |0.87 |0 |0.87 | |3 |75 |1.04 |0 |1.04 | |3.5 |75 |1.19 |0 |1.19 | |4 |75 |1.32 |0 |1.32 | |4.5 |75 |1.42 |0 |1.42 | |5 |75 |1.51 |0 |1.51 | |5.5 |75 |1.59 |0 |1.59 | |6 |75 |1.65 |0 |1.65 | |6.5 |75 |1.7 |0 |1.7 | |7 |75 |1.74 |0 |1.74 | |7.5 |75 |1.78 |0 |1.78 | |8 |75 |1.81 |0 |1.81 | |8.5 |75 |1.82 |0 |1.82 | |9 |75 |1.82 |0 |1.82 | |9.5 |75 |1.82 |0 |1.82...
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