Cardiac Conduction System

(1) Conduction System of Heart Conduction System = Heart Beat & Pumping Cardiac Contractions = Unconscious –Autonomic Nervous System  decrease or increase heart rate depending on circumstance

(2) Depolarization of the Heart Generate Action Potential & Depolarization: –Atria  Ventricles Depolarization Path: 1.SA Node  AV Node 2.Atria Contract 3.(Delay)  AV Bundle 4.Ventricles Contract (Blood ejected out of arteries, leaving heart)

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(3) Nodes & Bundles Sinoatrial Node (SA Node) –Right atrium –Starts each heart beat & sets rate –“Pacemaker” Atrioventricular Node (AV Node) = Left atrium AV Bundle = –Bundle Branches (along septum) –Purkinje Fibers (along entire muscular wall of heart)

(4) Cardiac Cycle Diastole = Relax –Blood passively filling atria Systole = Contract –Ventricles contract –Blood Ejected out of heart

(5) Diastole 1.Ventricles relax 2. Semilunar valves closed 3. Ventricular Presure < Atrial Pressure –AV valves open –Ventricles fill with blood 4. Atria contract and force blood remaining in chambers into ventricles

(6) Systole 1.Pressure increases in ventricles -Filled with blood 2.AV valves close 3. Pressure in ventricles > Arteries leaving heart -Semilunar valves open -Blood rushes out of ventricles 4. Atria are relaxed and begin to fill back up

(7) Heart Beat You hear something like “lub” “dup” –“lub” = closing of AV valves During ventricular systole –“dup” = closing of semilunar valves During early diastole You should NOT hear blood flow –You’ll hear it if flow is interrupted by blockage _sounds/heart.wav

(8) Cardiac Output Cardiac Output –A–Amount of blood pumped out by each ventricle / 1 minute –C–Cardiac Output = Heart Rate x Stroke Volume –C–CO = (HR)(SV) Stroke Volume –V–Volume of blood pumped out by ventricle –I–Increase of SV = Increase of ventricular force + contraction Average Stroke Volume = 0.2L Average Cardiac Output = 15L/min

(9) Starling’s Law Starling’s Law of the Heart: –Degree of cardiac muscle extension before contraction –Increase Extension = Stronger Contraction –Degree of Extension  result of percent filling of ventricles