Answer Happy

4) 4) Which of the following is the best explanation for why cardiac contractile fibers depolarize and contract in a defined pathway, ensuring the complete contraction cycle of the heart? A) The gap junctions at the intercalated discs allow for ion flow to conduct current from one fiber to the next in a defined pathway B) The SA node delivers the contraction signal to the right atrium, then the left atrium, and then the AV node delivers the contraction signal to the right ventricle and then the left ventricle. C) The flow of blood into each chamber causes first a stretch of the fibers, followed by a reflexive contraction of the fibers, ensuring that the heart continues to contract in the absence of current. D) The contraction signal produced by the SNS targets every fiber in a specific sequence. ) 5) 5) What causes the AV node delay represented by the P-R segment on the ECG tracing? A) The internodal pathways feed into the AV node through very indirect routes. B) It takes a certain amount of time for the Cat+ signal to be transferred to atrial contractile cells. C) AV node autorhythmic cells have a higher threshold than SA node autorhythmic cells.