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Transcript
HEART PHYSIOLOGY What a Job! It pushes your six liters of blood through your blood vessels over 1000 times a day! Thousands of cells function as one unit! Basic Heart Anatomy Note: Right & left are named based on position in the chest & seem reversed in a diagram Superior chambers = atria Small, limited muscle Inferior chambers = ventricles Large, heavily muscled Pumping chambers Septum divides ventricles Valves Prevent back-flow of blood Two atrioventricular (AV) valves: Tricuspid Bicuspid/mitral Two semilunar valves: Pulmonary Aortic Purpose? Pulmonary circuit Between heart & lungs Why? What is the pump? Systemic circuit Between heart & rest of body Why? What is the pump? Right Atrium Receives deoxygenated blood from Superior vena cava (from body above diaphragm) Inferior vena cava (from body below diaphragm) Coronary sinus (from heart) Passes blood through tricuspid valve to RV Left Atrium Receives oxygenated blood from lungs through: Right and left superior pulmonary veins Right and left inferior pulmonary veins Passes blood through the bicuspid/mitral valve to the LV Ventricles RV pumps deoxygenated blood to lungs through pulmonary semilunar valve into pulmonary trunk LV pumps oxygenated blood to body through aortic semilunar valve to aorta Cardiac Cycle = one heartbeat Systole – contraction of the ventricles Diastole – relaxation of the ventricles Events occur in 3 phases: 1: Mid-to-Late Diastole Heart in complete relaxation Low pressure Blood flowing into atria and ventricles Semi-lunar valves closed A-V valves open END – atria contract and force remaining blood into ventricles 2: Ventricular Systole Ventricles contract, increasing pressure A-V valves close Atria begin filling with blood END – Ventricular pressure > artery pressure Blood forced out semilunar valves 3. Early Diastole Ventricles relax, dropping pressure Semi-lunar valves close END – Atrial pressure > ventricular pressure Blood is forced through AV valves Heart Rhythm 1. 2. Intrinsic Conduction System (ICS) – “specialized” tissue sets basic rhythm, ~75 beats/minute Extrinsic Control – nervous system can increase or decrease heart rate Intrinsic Conduction System Starts with autorhythmic cells: 1. SA (sinoatrial) Node – “Pacemaker” - causes the atria to contract 2. AV (atrioventricular) Node – causes ventricles to contract Continues through rest of ICS: 3. Bundle of His 4. Bundle branches 5. Purkinje fibers Depolarization Sequence 1 2 3 4 5 Electrocardiogram [ECG/EKG] Traces the flow of current through the heart Cardiac Output Stroke Volume (SV) – Blood pumped per ventricle per heartbeat Cardiac Output (CO) – Blood pumped per ventricle per minute = Heart Rate (HR) * Stroke Volume (SV) Normal Adult HR is ~75 beats/minute Average resting SV is ~70 ml/beat What is the average adult CO? Irregular Heartbeats Tachycardia Bradycardia (>100 beats/min) (<60 beats/min) Ischemia – lack of adequate blood supply Fibrillation – rapid uncoordinated shuddering of heart muscle (major cause of heart attack/death)
