Transcript Slide 1
Cardiovascular: Heart Pericardium & Heart Wall p 718 p 722 Heart Valves Mass & Heat Flow Model Flow from high pressure to low pressure Driving Force? Resistance? p 737 Heart Valves ONE WAY flow p 718 Cardiac Conduction System = specialized myocytes that do not contract, instead generate action potentials Components •Sinoatrial Node •Atrioventricular Node •Atrioventricular Bundle •Bundle Branches •Purkinje Fibers p 729 Cardiac Muscle Myocardium has two networks; •Atrial network •Ventricular network Gap Junctions allow Na+ to pass through from cell to cell, so action potential can pass from myocyte to myocyte All myocytes in a network contract as a unit SA Node Physiology Membrane starts at -60 mV and slowly depolarizes as Na+ flows in thru leak channels (pacemaker potential) At -40 mV voltage-gated FAST Ca++ channels open and Ca++ flows into myocyte p 732 SA Node Physiology At about 0 mV, K+ channels open and K+ flows out Membrane repolarizes to -60 mV, when K+ channels close and pacemaker potential resumes p 732 SA Node Physiology 0 mV is an action potential in the SA node myocytes This action potential spreads throughout entire atrial network through the gap junctions = contraction p 732 Cardiac Conduction System Action potential traveling over atrial network reaches AV node in about 50 msec (1/20th of a second) Action potential is delayed in AV node about 100 msec due to fewer gap junctions This gives ventricles time to fill with blood Cardiac Conduction System Action potential travels down AV bundle, branches, & Purkinje fibers to many areas of ventricular network starting from the apex Action potential travels from these areas to rest of network thru gap junctions = contraction p 729 Myocardium Action Potential Resting membrane potential = -90 mV p 733 Systole = period of contraction Diastole = period of relaxation End-systolic Volume (ESV) = volume of blood remaining in one ventricle at the end of systole End-diastolic Volume (EDV) = volume of blood remaining in one ventricle at the end of diastole Preload = amount of tension in ventricular myocardium right before systole Greater EDV = greater preload p 734 Cardiac Cycle p 739 Cardiac Output (CO) = volume of blood ejected from each ventricle in one minute Stroke Volume (SV) = volume of blood ejected from each ventricle in one systole Heart rate = contractions (beats) in one minute EDV minus ESV = ? SV times heart rate = ?