IBHRE Exam Questions with Answers

IBHRE Exam Questions with Answers Functional Refractory Period (FRP) - Answer-the coupling interval which first results in a measurable degree of delay in impulse conduction effective refractory period - Answer-the longest coupling interval to be associated with block resting (transmembrane) potential - Answer-the voltage difference between the inside and outside of the cell fiber (negative inside cell) action potential - Answer-the cellular characteristics of depolarization and repolarization. Consists of 5 phases (0-4) Phase 0 of action potential - Answer-the depolarization phase. during this phase, th rapid sodium channels are stimulated to open, causing the resting transmembrane potential to spike from about -90 mV to about 0 mV. Phase 1 of action potential - Answer-Early repolarization Phase 2 of action potential - Answer-the plateau phase. this phase, mediated by the slow calcium channels, essentially disrupts and delays repolarization started in phase 1 and prolongs the refractory period Phase 3 of action potential - Answer-the end of repolarization. Note: the period beginning at the end of phse 0 through the end of phase 3 is the refractory period of cardiac tissue. (opening of K+ channels, K+ out (closing of ca+ channels)) Phase 4 of action potential - Answer-the resting phase. It is during this phase that, in some cardiac cells, ions leak back and forth between membranes and cause a gradual increase in the transmembrane (resting) potential. Automaticity - Answer-The spontaneous depolarization to threshold, characteristic of cardiac pacemaker cells. AR interval - Answer-this begins when the atrial escape interval is allowed to time out completely