BIOL273 Chapter Notes - Chapter 3: Calcium Atpase, Neuromuscular Junction, Endoplasmic Reticulum
11 Sep 2016
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Relaxation: to end contraction, calcium must be removed from cytosol. Sarcoplasmic reticulum pumps ca2+ back into lumen using ca2+ atpase. As the concentration decreases, calcium releases from troponin, which allows tropomyosin to slide back and block actin"s myosin binding site. As crossbridges release, muscle fibre relaxes with help of elastic fibres in the sarcomere and in the connective tissue of the muscle. Fatigue: a reversible condition in which a muscle is no longer able to generate or sustain the expected power out. Central fatigue mechanism: arises in central nervous system. Peripheral fatigue mechanism: arises anywhere between neuromuscular junction and contractile elements of muscle. Possible cause of central fatigue is low ph due to acid production during atp hydrolysis but homeostatic mechanisms usually monitor the level of ph, so this would only apply in causes of maximum exertion. Neural causes of fatigue could arise from communication failure at the neuromuscular junction or from failure of the cns command neurons.
