KINS 1224 Chapter Notes - Chapter 19.4-19.6: Reticular Formation, Limit Set, Cell Membrane
29 Jan 2018
School
Department
Course
Professor
Document Summary
19. 4 electrical and contractile activity of the heart. How the electrical events in the heart produce its cycle of contraction and relaxation. Sinus rhythm: sa node that triggers the normal heart beat. If sa node is damaged, may take over rhythm. If sa or av is not working, ectopic foci fire at 20-40 bpm. Pacemaker potential: mp starts at -60 mv and drifts upward. Slow inflow of na+ with a compensating outflow of k+ Depolarization: threshold reaches -40mv, voltage-gated channels open and ca flows in. Repolarization: k channels open and k leaves cell. When repolarization is complete, k channels close and pacemaker potential starts over. Depolarization of sa node sets off one heart beat. Impulses in av node are slower because cardiocytes are thinner and less gap junctions for the signal to be transmitter. Delay is essential because it gives ventricles time to fill with blood before they contract lows s for contract.
