BIO310H5 Study Guide - Final Guide: Artificial Cardiac Pacemaker, Atrioventricular Node, Cardiac Muscle
Document Summary
Ganglia situated within the heart & act as pacemaker. Cells innervated by excitatory & inhibitory nerves: can alter heart rate. Specialized muscle cells capable of spontaneous activity (absence of stable rp)- weakly contractile. All cardiac cells= electrically coupled, ones with fastest intrinsic activity will stimulate whole heart & determine hr- if pacemaker stopped, other pacemaker cells will take over to produce lower hr (latent pacemaker) T wave= ventricular repolarization: where is the atrial repolarization? through qrs complex. Do not have stable resting potential: after each ap, membrane undergoes steady depolarization, = pacemaker potential. Fast depolarization brings membrane to firing level sooner & leads to faster heart rate. Acetylcholine slows heart by increasing k conductance (also reduces ca conductance) of pacemaker cells. Therefore slows down depolarization and therefore delays time to threshold. Acetylcholine released from ps neurons works on muscarinic receptors. Depolarization slower & time to reach threshold takes longer (frequency decreases)
