Essay on Skeletal Muscle Physiology

5322 Words May 27th, 2011 22 Pages
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Skeletal Muscle Physiology
O B J E C T I V E S 1. To define these terms used in describing muscle physiology: multiple motor unit summation, maximal stimulus, treppe, wave summation, and tetanus. 2. To identify two ways that the mode of stimulation can affect muscle force production. 3. To plot a graph relating stimulus strength and twitch force to illustrate graded muscle response. 4. To explain how slow, smooth, sustained contraction is possible in a skeletal muscle. 5. To graphically understand the relationships between passive, active, and total forces. 6. To identify the conditions under which muscle contraction is isometric or isotonic. 7. To describe in terms of length and force the
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During contraction, the myofilaments are sliding past each other, and the muscle shortens. Relaxation takes place when contraction has ended and the muscle returns to its normal resting state and length. The first activity you will conduct simulates an isometric, or fixed length, contraction of an isolated skeletal muscle. This activity allows you to investigate how the strength and frequency of an electrical stimulus affect whole muscle function. Note that these simulations involve indirect stimulation by an electrode placed on the surface of the muscle. This differs from the situation in vivo where each fiber in the muscle receives direct stimulation via a nerve ending. In other words, increasing the intensity of the electrical stimulation mimics how the nervous system increases the number of motor units activated.

left of the oscilloscope display is an indicator of passive force. After the muscle is stimulated, the Measure button at the right edge of the electrical stimulator becomes active. When the Measure button is clicked, a vertical orange line will be displayed at the left edge of the oscilloscope display. Clicking the arrow buttons below the Measure button moves the orange line horizontally across the screen. The Time window displays the difference in time between the zero point on the

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