Biol 216 8 Muscles 65-96.pdf - Muscle Fiber Responses...

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5/23/17 1 Muscle Fiber Responses: Muscle Twitch A single action potential arriving at a neuromuscular junction causes a muscle twitch Re-stimulation of a muscle fiber before it relaxes completely causes a second twitch, which is added to the first, causing a summed, stronger contraction 5/23/17 65 Muscle Fiber Responses:Tetanus Rapid arrival of APs causes twitches (contractions) to sum to a peak level of contraction called tetanus Tetanus : increasing the force of contraction of individual fibers 5/23/17 66
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5/23/17 2 9-67 Muscle Fiber Responses:Tetanus Rapid arrival of APs causes twitches (contractions) to sum to a peak level of contraction called tetanus Tetanus : increasing the force of contraction of individual fibers Note: Tetanus also refers to a medical condition characterized by a prolonged contraction of skeletal muscle fibers caused by the bacterium: Clostridium tetani . Infection generally occurs through wound contamination and often involves a cut or deep puncture wound. As the infection progresses, muscle spasms develop in the jaw (thus the name "lockjaw") and elsewhere in the body.Infection can be prevented by proper immunization . 5/23/17 a. Single twitches b. Summed twitches c. Tetanus Tetanus Twitch summation Stimulation ceases or fatigue begins Single twitch Relative tension Contractile activity Action potentials Time If a muscle fiber is restimulated after it has completely relaxed, the second twitch is the same magnitude as the first twitch. If a muscle fiber is restimulated before it has completely relaxed, the second twitch is added on to the first twitch, resulting in summation. If a muscle fiber is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli, a peak level of continuous contraction known as tetanus occurs. Membrane potential (mV) 5/23/17 68
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5/23/17 3 Types of Muscle Fibers 1. Slow muscle fibers [SO: slow oxidative] 2. Fast aerobic ( or fast oxidative glycolytic fibers) [FOG] 3. Fast anaerobic fibers [fast glycolytic FC] 5/23/17 69 Types of Muscle Fibers (1) Muscle fibers differ in number of mitochondria and capacity to produce ATP 1.
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