BMS 420 Lecture Notes - Sinus Rhythm, Cardiac Output, Electrocardiography
Document Summary
T tubules extend from sarcolemma and permit extracellular ions and fluid to diffuse near intracellular structures. Sarcoplasmic reticulum stores substantial amounts of ca++ which is released when ryanodine receptors are stimulated by extracellular ca++ which flow through l type voltage sensitive dihydropyridine receptors. Ryanodine receptors activated by calcium, initiate calcium release. Intercalated discs allow low resistance for charge to flow from cell to cell. Ca++ enters cytoplasm via vg l-type ca++ channels which interact with ryanodine receptors on. Tropomyosin is associated with three regulatory proteins: tn-t, tn-c, and tn-i. Ca++ binds to tn-c which in presence of atp changes conformation of troponin. Myosin and actin cross-bridge when myosin binding sites exposed on actin. Serca-resequesters ca++ via phosphorylation of phospholamban (serca = spendoreticulum. Calsequestrin is the primary calcium storage protein in the sr. + ions per molecule during diastole which prevents ca++ precipitation. Ca++ releases from tn-c and inhibition of binding sites occurs relaxation.
