Cardiac Cycle-1.pptx for medical students

Medical

1. CARDIAC CYCLE

2. Introduction Definition : Cardiac cycle is defined as the sequence of c oordinated events taking place in the heart during each beat. Events: Systole (Contraction) Diastole (Relaxation)

3. Duration Heart rate: 72/minute Cardiac cycle: 0.8 second Events of cardiac cycle 1 . Atrial events 2. Ventricular events

4. Atrial events 1. Atrial systole = 0.11 (0.1) sec 2. Atrial diastole = 0.69 (0.7) sec Ventricular events 1 . Ventricular systole = 0.27 (0.3) sec 2. Ventricular diastole = 0.53 (0.5) sec

5. Ventricular Systole Time (second) 1. Isometric contraction = 0.05 2. Ejection period = 0.22 0.27 Ventricular Diastole 1. Protodiastole = 0.04 2. Isometric relaxation = 0.08 3. Rapid filling = 0.11 4. Slow filling = 0.19 5. Last rapid filling = 0.11 0.53

6. Atrial systole Duration: 0.11 second Known as last rapid filling phase or presystole Intra atrial pressure increases Contraction of atrial musculature causes the production of fourth heart sound

7. Atrial diastole Duration: 0.69 sec (0.7sec) A trial filling takes place atrial diastole (first 0.3 sec) coincides with ventricular systole > heart relaxes as a whole for 0.4 sec

8. Ventricular events ISOMETRIC CONTRACTION PERIOD characterized by increase in tension, without any change in the length of muscle fibers A lso called isovolumetric contraction Closure of atrioventricular valves at the beginning of this phase produces first heart sound . Significance : P ressure rise in ventricle, causes opening of semilunar valves

9. 2. EJECTION PERIOD Duration: 0.22 second Blood is ejected out of both the ventricles due to the opening of semilunar valves and isotonic contraction of ventricles 1. First Stage or Rapid Ejection Period S tarts immediately after the opening of semilunar valves. L arge amount of blood is rapidly ejected from both the ventricles. Duration: 0.13 second. 2. Second Stage or Slow Ejection Period B lood is ejected slowly with much less force. Duration: 0.09 second.

10. 1. PROTODIASTOLE Duration: 0.04 second first stage of ventricular diastole Events : Due to the ejection of blood, the pressure in aorta and pulmonary artery increases and pressure in ventricles drops Closure of Semilunar valves produces second heart sound

11. 2. ISOMETRIC RELAXATION PERIOD Duration: 0.08 second C haracterized by decrease in tension without any change in the length of muscle Isometric relaxation Reduces ventricular pressure O pening of atrioventricular valves, F illing of ventricles

12. 3. RAPID FILLING PHASE Duration: 0.11 second S udden rush of blood from atria into ventricles 70% of ventricular filling takes place Significance: P roduction of third heart sound

13. 4. SLOW FILLING PHASE Duration: 0.19 second ventricular filling becomes slow 20% of ventricular filling takes place

14. 5 . LAST RAPID FILLING PHASE O ccurs because of atrial systole After slow filling period, the atria contract and push a small amount of blood into ventricles ( atrial kick) 10% of ventricular filling takes place End-diastolic Volume: amount of blood remaining in each ventricle at the end of diastole. It is about 130 to 150 mL per ventricle.

15. INTRA-ATRIAL PRESSURE R esponsible for: Opening of the atrioventricular valves Ventricular filling D evelopment of venous pulse

16. Heart sounds HEART SOUNDS 1 st Heart Sound > Closure AV valves 2 nd Heart Sound > Closure of Semilunar valves 3 rd Heart Sound > Sudden rush blood from Atria to ventricles 4 th Heart Sound > Contraction of Atrial musculature

17. Thank you