UZ CVS LECTURES 2024 DR F MAUNGANIDZE PART I RECORDED LECTURE 1 [Autosaved] (1).pdf

UNIVERSITY OF ZIMBABWE FACULTY OF MEDICINE AND HEALTH SCIENCES CARDIOVASCULAR PHYSIOLOGY DR FABIAN MAUNGANIDZE  PART I THE HEART AND THE CIRCULATORY SYSTEM LECTURE 1   Weight of the heart 300g  Work: 75/min, 108000...

UNIVERSITY OF ZIMBABWE FACULTY OF MEDICINE AND HEALTH SCIENCES CARDIOVASCULAR PHYSIOLOGY DR FABIAN MAUNGANIDZE  PART I THE HEART AND THE CIRCULATORY SYSTEM LECTURE 1   Weight of the heart 300g  Work: 75/min, 108000 beats /day  35 million beats /year, 2.5 billion beats/life  70ml/beat, 7200 l/day The work of the heart in one life is equivalent to lifting 30 tons to the top of Mount Everest It’s a busy and hard working heart!  MAIN FUNCTIONS OF THE CIRCULATORY SYSTEM  Transport and distribute essential substances to the tissues.  Remove metabolic byproducts.  Adjustment of oxygen and nutrient supply in different physiologic states.  Regulation of body temperature.  Humoral communication. Systemic and Pulmonary Circulation B. Heart Chambers B. Heart Chambers  1. Right Heart  receives venous blood from systemic circulation  via superior and inferior vena cava into right atrium  pumps blood to pulmonary circulation from right ventricle  2. Left Heart  receives oxygenated blood from pulmonary circulation  pumps blood into systemic circulation  C. Heart Valves  1. Atrioventricular  tricuspid--between RA and RV; three leaflets  mitral--between LA and LV; two leaflets  2. Semilunar  pulmonic--three leaflets  aortic--three leaflets  Heart Valves  Prevent backward regurgitation  Provide low resistance to forward flow  Section 1 The Heart as a Pump 1. Cardiac Cycle  The period from the end of one heart contraction to the end of the next  Cardiac Cycle  Diastole is longer than systole  The sequence of systole and diastole Cardiac Cycle: diastole and systole Diastole Systole 2 The Phases of the Cardiac Cycle (1) Period of isometric (isovolumetric or isovolumic) contraction Events: ventricular contraction ventricular pressure rise atrioventricular valve close the ventricular pressure increase sharply Period: 0.05 sec Importance: enable the ventricular pressure to rise from 0 to the level of aortic pressure (after-load) (2) Period of ejection Events: ventricular contraction continuously the ventricular pressure rise above the arterial pressure semilumar valves open blood pours out of the ventricles  Rapid ejection period (0.10s, 60% of the stroke volume)  Reduced ejection period (0.15s, 40% of the stroke volume) (3) Period of isometric (isovolumic) relaxation Events: ventricular muscle relax the ventricular pressure fall lower than the aortic pressure aortic valve close the ventricular pressure fall sharply Period: 0.06-0.08 s Importance: Enables the ventricular pressure to fall to the level near the atrial pressure (4) Period of filling of the ventricles Events: Ventricular muscle relax continuously the ventricular pressure is equal or lower than the atrial pressure atrioventricular valve open blood accumulated in the atria rushes into the ventricular chambers quickly from the atrium to the ventricle.  Period of rapid filling. (0.11s, amount of filling, 2/3)  Period of reduced filling (0.22s, little blood fills into the ventricle) (5) Atrial systole  Significance, 30% of the filling  Be of major importance in determining the final cardiac output during high output states or in the failing heart  LEFT VENTRICULAR LEFT VENTRICULAR PRESSURE (mmHg) PRESSURE/VOLUME P/V LOOP 120 F E 80 D 40 A B C 0 50 100 150 LEFT VENTRICULAR VOLUME (ml) 2） Pressure changes in the atria, the a, c, and v waves.  a wave, the atrial contraction  c wave, bulging of the A-V valves when the ventricles begin to contract  v wave, at the end of ventricle contraction,  caused by the accumulated blood in the atria while the A-V valves are closed  END OF LECTURE 1