Heatproduction

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Unformatted text preview: is stopped. • The accumulation of lactic acid causes hard breathing and enough discomfort that to stop muscle activity until homeostasis is restored. Muscle Tissue and Homeostasis • Muscle Fatigue­ the inability of muscles to maintain its strength of contraction – related to • • • • insufficient energy insufficient oxygen depletion of glycogen build up of lactic acid – lactic acid increase causes a decrease in the pH ( increase in hydrogen ion concentration) – thus, muscle fatigue is viewed as a homeostatic mechanism to prevent pH levels from dropping below the normal acceptable range for the cellular environment. • Heat Production­ – 85% of the energy of muscle contraction is given off as heat to help maintain body temperature. • shivering when cold Kinds of Muscular Contraction Twitch Contraction­ a brief contraction of all the muscle fibers in a motor unit in response to a single action potential. • Four phases – latent period­ calcium is released from the sarcoplasmic reticulum and myosin head activity begins – contraction phase – relaxation phase – refractory period­ period of lost excitability (cardiac muscles have a long refractory period) Refrractory Refactory Peeriod P riod Kinds of Muscular Contration Tetanus­ sustained muscle contraction • incomplete tetanus­ when concurrent stimuli is applied such that the muscle only partially relaxes (wave summation) • complete tetanus­ stimuli is applied such that the muscle does not relax all – most muscle action is of this type Kinds of Muscular Contraction Isotonic Contraction­ the muscle shortens and pulls on another structure, such as bone. • Tension remains constant and energy is expended Isometric Contraction­ there is minimal shortening of the muscle. • Tension increa...
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