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lecture29 - Ca pump in SR no longer removes Ca 2 Nov...

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1 Nov 11­11:05 AM Nov 11­12:12 PM Muscle Relaxing factor in muscle Tropomyosin can block the access of myosin to actin. Position of tropomyosin is controlled by troponin C, hwich interacts with the other troponin components to cause the tropomyosin to move so that myosin can interact with actin. Troponin C becomes activated by the presence of Ca++ ions. When Ca is removed, the tropomyosin shifts position and myosin can no longer bind to actin. >>>muscle relaxes. Maintained by a pumping system in the sarcoplasmic reticulum that controls the cellular concentration of Ca++ Ca++ pump ­ removes Ca++ from the cytoplasm into the SR Ca Channel (ryanodine) that is voltage sensitive, and opens in response to a voltage change carried to the SR by the Tubule system. Calsequestrin in the cisterna of the SR. When an animal dies ­­ ATP synthesis stops ­ cell uses up its stores of ATP Myosin bound to actin can't release
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Unformatted text preview: Ca++ pump in SR no longer removes Ca++ 2 Nov 11­12:26 PM Cells Cells contain actin, soluble and fiber forms Cells contain myosin (cytoplasmic myosin) ­­allows cellular shape change and motility. Look at Smooth muscle. Actin and Myosin Myosin Light Chain ­ in smooth muscle, the MLC, controls the access of the myosin to actin. Ability of MLC to interact with actin depends on its phosphorylation state. In order for smooth muscle to contract, it is necessary for MLC to be phosphorylated The enzyme that carries this out is Myosin Light Chain Kinase (Kinase is an enzyme that causes phosphorylation) ­­MLCK MLCK is inactive, and needs to be activated in order for the muscle to contract. Activation occurs through binding to a small protein ­ calmodulin. ­­ Calmodulin binds Ca++ and is only able to activate MLCK when it has bound Ca++ Nov 11­12:41 PM 3 Nov 10­11:55 AM...
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lecture29 - Ca pump in SR no longer removes Ca 2 Nov...

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