Electrical Activity of the Heart fully solved 2023

Electrical Activity of the HeartWhat is an action potential? - correct answer Rapid change in the transmembrane potential followed by a return to the resting membrane potential When do changes in transmembrane potential occur? - correct answer During changes in the permeability of the cell membrane to intracellular and extracellular ions Is the duration of APs in cardiac cells shorter or longer than in nerves cells or skeletal/smooth muscle? - correct answer Much longer What is the effective refractory period? - correct answer Interval from the beginning of the AP until the time the fiber can conduct another AP What is the relative refractory period? - correct answer -Interval during which an AP may be evoked; magnitude and/or rate of depolarization of AP varies -Differs depending on slow vs fast response cardiac cells What is the fast response in terms of the relative refractory period? - correct answer -When fast response is evoked during RRP of a previous excitation, characteristics vary with the membrane potential that exists at the time of stimulation -The LATER in the RRP the fiber is stimulated -> the greater is the increase in amplitude of the response and in the slope of the upstroke What is the slow response in terms of RRP? - correct answer -Post repolarization refractoriness = even after cell has completely repolarized, it may be difficult to evoke a propagated response for some time -The lengthy refractory periods also explain why conduction tends to be blocked in slow response fibers What is conduction velocity? - correct answer -Speed at which an AP is transmitted or communicated from cardiac muscle cell to cardiac muscle cell -Property of cardiac muscle cells How does a myocardial infarction affect the RMP? - correct answer Dysfunctional Na/K pump -> High levels of extracellular K -> makes RMP less negative How does renal failure affect the RMP? - correct answer Renal failure = reduction in excretion -> blood K levels increase -> extracellular K increases -> RMP becomes less negative What types of channels do slow response cells have? - correct answer -Have spontaneously opening Na channels -These allow for automaticity -Do NOT have voltage gated Na channels What is the conduction velocity of the AV node? - correct answer 0.05 m/s What is the conduction velocity of the atria/ventricles (contractile)? - correct answer 1 m/s What is the conduction velocity of Purkinje cells (conducting)? - correct answer 4 m/s What is the slow response more prone to than the fast response? - correct answer Conduction blocks What is a functional syncytium? - correct answer When a stimulus is applied to any one part of the cardiac muscle -> it is propagated to all cells and results in contraction of the entire muscle *All or nothing response* What structural features establish the electrochemical linkage between cardiac muscle cells? - correct answer -Intercalated disks -Connexons What are the 2 basic functions of the specialized cardiac muscle cells that form the conduction system of the heart? - correct answer -Initiation of cardiac APs (automaticity) -Propagation of cardiac APs throughout the heart in a coordinated and organized fashion (rhythmicity)