Contraction ceases only once calcium has beenremoved from the cytosolThis occurs through two mechanism:l. calcium is pumped out of the cell via theelectrogenic Na-Ca exchanger, which pumps twocalcium ion out for every three sodium ions in.2. calcium is re-uptaked into sarcoplasmicreticulum stores by a Ca ATPase pump
Contraction ceases only once calcium has been removed from the cytosol This occurs through two mechanism: 1. calcium is pumped out of the cell via the electrogenic Na-Ca exchanger, which pumps two calcium ion out for every three sodium ions in. 2. calcium is re-uptaked into sarcoplasmic reticulum stores by a Ca ATPase pump
Ca++ is removedby re-uptake intoNa+/Ca++Na+/K+Voltage-sensitiveslowthe sarcoplasmicreticulum and byCa++ channelATPaseenchangeextrusion from theNa+K+Ca++Ca++Na+cell by this systemMembraneofATPcardiacmuscleSodium balanceCa++is restored byK+Ca++Na+Na+Na+/K+ATPase口Ca++ storesCa++ entry from outside the cell triggers the(sarcoplasmicrelease ofa much larger quantity of Ca++from thereticulum)sarcoplasmic reticulum八Free Ca++Increased Ca++ concentrationAactinactininitiates the contractile processMyosin
Membrane of cardiac muscle ATP Voltage-sensitive slow Ca++ channel Na+/Ca++ enchange Ca++ Ca++ Ca++ Ca++ Na+ Na+ Na+ Na+ K+ K+ Na+/K+ ATPase Ca++ is removed by re-uptake into the sarcoplasmic reticulum and by extrusion from the cell by this system Sodium balance is restored by Na+/K+ ATPase Ca++ stores (sarcoplasmic reticulum) Free Ca++ Myosin Ca++ entry from outside the cell triggers the release of a much larger quantity of Ca++ from the sarcoplasmic reticulum Increased Ca++ concentration actin actin initiates the contractile process
Processes of cardiac contraction1. the intracellular levels of calcium rise tolevels 10 000 times greater than those at rest.2. calcium binds to troponin C3. then modifying the position of actin andmyosin filaments, andallowing contraction
Processes of cardiac contraction 1. the intracellular levels of calcium rise to levels 10 000 times greater than those at rest. 2. calcium binds to troponin C 3. then modifying the position of actin and myosin filaments, and allowing contraction
L-Type Calcium ChannelCa2+ATPCAMPAdenylate cyclaseATPaseCa2tCa2+G-proteinRyanodineβ-AdrenergicReceptorReceptorOCa2+Ca2+ATPaseot-AdrenergicReceptorSarcoplasmicReticulumO2Ca2+3NatCa2+Angiotensin IIReceptor2K+ATPase3NaContractile Protcins
The bodyattempts to compensate for theeffects of CHF by two processes-extrinsic and intrinsicExtrinsic neurohumoral reflexes:a. Extrinsic neurohumoral reflexes aim to maintaincardiac output and blood pressureb. activation of baroreceptorsc. increased sympathetic activityincreased heart rate and vasoconstriction,increased cardiac contractility and vascular tone,increased cardiac afterload
The body attempts to compensate for the effects of CHF by two processes ——extrinsic and intrinsic Extrinsic neurohumoral reflexes: a. Extrinsic neurohumoral reflexes aim to maintain cardiac output and blood pressure b. activation of baroreceptors c. increased sympathetic activity increased heart rate and vasoconstriction, increased cardiac contractility and vascular tone, increased cardiac afterload