PHSI 208 Lecture Notes - Lecture 27: Purkinje Fibers, Atrioventricular Node, Bradycardia
Document Summary
Sa node internodal pathways av node bundle of his bundle branches purkinje fibers. Cardiac ap originates in a group of ells in the sa node (pacemaker) and spreads through a network of autorhythmic cells. The av node and pukinje fibers have slower pacemaker activity over ridden by that of the sa node. The group of autorhythmic cells w/ the most rapid pacemaker activity set the heart rate: they have different intrinsic firing rates (due to different concentration of hcn channels) If the cells in the sa node becomes damaged the av node will take over (it will spontaneously generate ap"s, and passes it to the internodal pathways and the down to the ventricles) The sa node generates electrical impulses that causes both atria to contract. The av node delays the passage of the electrical impulses to the ventricles this delay ensures that the atria have ejected all the blood into the ventricles before the ventricles contract.
