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CARDIAC CYCLE.pptx

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CharlesSsekawu

The document describes the cardiac cycle and its key events. The cardiac cycle consists of systole, when the heart contracts and pumps blood, and diastole, when the heart relaxes and fills with blood. Each cycle takes approximately 0.8 seconds. Systole includes the isometric contraction, when pressure rises but volume does not change, and the ejection period, when blood is pumped out. Diastole includes isometric relaxation as pressure falls, followed by three filling phases - rapid, slow, and last rapid filling due to atrial contraction. The document provides details on the timing and mechanics of each phase of the cardiac cycle.

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CARDIAC CYCLE Dr. Ssekawu Charles
Cardiac Cycle • is defined as the succession of (sequence of) coordinated events taking place in the heart during each beat. • Each heartbeat consists of two major periods called systole and diastole. • During systole, heart contracts and pumps the blood through arteries. • During diastole, heart relaxes and blood is filled in the heart. • heart beats at a normal rate of 72/minute, duration of each cardiac cycle is about 0.8 second
EVENTS OF CARDIAC CYCLE • ATRIAL EVENTS (divided into two divisions) 1. Atrial systole = 0.11 (0.1) sec 2. Atrial diastole = 0.69 (0.7) sec. • „VENTRICULAR EVENTS (divided into two divisions) 1. Ventricular systole = 0.27 (0.3) sec 2. Ventricular diastole = 0.53 (0.5) sec. • In clinical practice, the term ‘ – systole’ refers to ventricular systole 0.27 – (divided into two subdivisions ) 1. Isometric contraction = 0.05 2. Ejection period = 0.22 – diastole’ refers to ventricular diastole 0.53 – (divided into five subdivisions) 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
CARDIAC CYCLE.pptx
NOTE • Among the atrial events, atrial systole occurs during the last phase of ventricular diastole. Atrial diastole is not considered as a separate phase, since it coincides with the whole of ventricular systole and earlier part of ventricular diastole.
DESCRIPTION OF ATRIAL EVENTS
ATRIAL SYSTOLE • also known as last rapid filling phase or presystole • considered as the last phase of ventricular diastole. • Its duration is 0.11 second. • only a small amount, i.e. 10% of blood is forced from atria into ventricles. • Atrial systole is not essential for the maintenance of circulation • persons with atrial fibrillation survive for years, without suffering from circulatory insufficiency. However, such persons feel difficult to cope up with physical stress like exercise. Pressure and Volume Changes • During atrial systole, the intraatrial pressure increases. • Intraventricular pressure and ventricular volume also increase but slightly. Fourth Heart Sound • Contraction of atrial musculature causes the production of fourth heart sound.
CARDIAC CYCLE.pptx
ATRIAL DIASTOLE • After atrial systole, the atrial diastole starts. Simultaneously, • ventricular systole also starts. • Atrial diastole lasts for about 0.7 sec (accurate duration is 0.69 sec). • This long atrial diastole is necessary because, this is the period during which atrial filling takes place. • Right atrium receives deoxygenated blood from all over the body through superior and inferior venae cavae. • Left atrium receives oxygenated blood from lungs through pulmonary veins.
Atrial Events Vs Ventricular Events
DESCRIPTION OF VENTRICULAR EVENTS
ISOMETRIC CONTRACTION PERIOD • is the first phase of ventricular systole and lasts for 0.05 second • It is the type of muscular contraction characterized by increase in tension, without any change in the length of muscle fibers. • Isometric contraction of ventricular muscle is also called isovolumetric contraction. • Immediately after atrial systole, the atrioventricular valves are closed due to increase in ventricular pressure. • Semilunar valves are already closed. • ventricles contract as closed cavities, in such a way that there is no change in the volume of ventricular chambers or in the length of muscle fibers. • Only the tension increases in ventricular musculature. • Because of increased tension in ventricular musculature during isometric contraction • the pressure increases sharply inside the ventricles.
ISOMETRIC CONTRACTION PERIOD First Heart Sound • Closure of atrioventricular valves at the beginning of this phase produces first heart sound. Significance of Isometric Contraction • The ventricular pressure increases greatly above the pressure in the aorta and pulmonary artery, the semilunar valves open. • Thus, the pressure rise in ventricle, caused by isometric contraction is responsible for the opening of semilunar valves, leading to ejection of blood from the ventricles into aorta and pulmonary artery.
EJECTION PERIOD • Due to the opening of semilunar valves and isotonic contraction of ventricles, • blood is ejected out of both the ventricles. Hence, this period is called ejection period. • Duration of this period is 0.22 second. Ejection period is of two stages 1. First Stage or Rapid Ejection Period • starts immediately after the opening of semilunar valves. • large amount of blood is rapidly ejected from both the ventricles. • It lasts for 0.13 second. 2. Second Stage or Slow Ejection Period • the blood is ejected slowly with much less force. • Duration of this period is 0.09 second.
EJECTION PERIOD End-systolic Volume • Ventricles are not emptied at the end of ejection period and some amount of blood remains in each ventricle. • Amount of blood remaining in ventricles at the end of ejection period (i.e. at the end of systole) is called endsystolic volume. • It is 60 to 80 mL per ventricle. • Measurement of end-diastolic volume End systolic volume is measured by radionuclide angiocardiography (multigated acquisition – MUGA scan) and echocardiography. • It is also measured by cardiac catheterization, computed tomography (CT) scan and magnetic resonance imaging (MRI) Ejection Fraction • refers to the fraction (or portion) of end diastolic volume that is ejected out by each ventricle per beat. • From 130 to 150 mL of end diastolic • volume, 70 mL is ejected out by each ventricle (stroke volume). • Normal ejection fraction is 60% to 65%.
PROTODIASTOLE • is the first stage of ventricular diastole, • Duration of this period is 0.04 second. • Due to the ejection of blood, the pressure in aorta and pulmonary artery increases and pressure in ventricles drops. • When intraventricular pressure becomes less than the pressure in aorta and pulmonary artery, the semilunar valves close. • Atrioventricular valves are already closed • protodiastole indicates only the end of systole and beginning of diastole. Second Heart Sound • Closure of semilunar valves during this phase produces second heart sound
ISOMETRIC RELAXATION PERIOD • is the type of muscular relaxation, characterized by decrease in tension without any change in the length of muscle fibers. • Isometric relaxation of ventricular muscle is also called isovolumetric relaxation • During isometric relaxation period, once again all the • valves of the heart are closed • both the ventricles relax as closed cavities without any change in volume or length of the muscle fiber. • Intraventricular pressure decreases during this period. • Duration of isometric relaxation period is 0.08 second. Significance of Isometric Relaxation • the ventricular pressure decreases greatly. When the ventricular pressure becomes less than the pressure in the atria, atrioventricular valves open. Thus, the fall in pressure in the ventricles, caused by isometric relaxation is responsible for the opening of atrioventricular valves, resulting in filling of ventricles.
RAPID FILLING PHASE • When atrionventricular valves are opened, • sudden rush of blood (which is accumulated in atria during atrial diastole) from atria into ventricles. • This period is called the first rapid filling period. • Ventricles also relax isotonically. About 70% of filling takes place during this phase, which lasts for 0.11 second. Third Heart Sound • Rushing of blood into ventricles during this phase causes production of third heart sound.
SLOW FILLING PHASE • After the sudden rush of blood, the ventricular filling becomes slow • It is also called diastasis. About 20% of filling occurs in this phase. • Duration of slow filling phase is 0.19 second. „LAST RAPID FILLING PHASE • Last rapid filling phase occurs because of atrial systole. • After slow filling period, the atria contract and push a small amount of blood into ventricles. • About 10% of ventricular filling takes place during this period. • Flow of additional amount of blood into ventricle due to atrial systole is called atrial kick. End-diastolic Volume • is the amount of blood remaining in each ventricle at the end of diastole. • It is about 130 to 150 mL per ventricle.
CARDIAC CYCLE.pptx
ASSIGNMENT • Intra-atrial pressure changes during cardiac cycle • Intraventricular pressure changes during cardiac cycle

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CARDIAC CYCLE.pptx

  • 2. Cardiac Cycle • is defined as the succession of (sequence of) coordinated events taking place in the heart during each beat. • Each heartbeat consists of two major periods called systole and diastole. • During systole, heart contracts and pumps the blood through arteries. • During diastole, heart relaxes and blood is filled in the heart. • heart beats at a normal rate of 72/minute, duration of each cardiac cycle is about 0.8 second
  • 3. EVENTS OF CARDIAC CYCLE • ATRIAL EVENTS (divided into two divisions) 1. Atrial systole = 0.11 (0.1) sec 2. Atrial diastole = 0.69 (0.7) sec. • „VENTRICULAR EVENTS (divided into two divisions) 1. Ventricular systole = 0.27 (0.3) sec 2. Ventricular diastole = 0.53 (0.5) sec. • In clinical practice, the term ‘ – systole’ refers to ventricular systole 0.27 – (divided into two subdivisions ) 1. Isometric contraction = 0.05 2. Ejection period = 0.22 – diastole’ refers to ventricular diastole 0.53 – (divided into five subdivisions) 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
  • 5. NOTE • Among the atrial events, atrial systole occurs during the last phase of ventricular diastole. Atrial diastole is not considered as a separate phase, since it coincides with the whole of ventricular systole and earlier part of ventricular diastole.
  • 7. ATRIAL SYSTOLE • also known as last rapid filling phase or presystole • considered as the last phase of ventricular diastole. • Its duration is 0.11 second. • only a small amount, i.e. 10% of blood is forced from atria into ventricles. • Atrial systole is not essential for the maintenance of circulation • persons with atrial fibrillation survive for years, without suffering from circulatory insufficiency. However, such persons feel difficult to cope up with physical stress like exercise. Pressure and Volume Changes • During atrial systole, the intraatrial pressure increases. • Intraventricular pressure and ventricular volume also increase but slightly. Fourth Heart Sound • Contraction of atrial musculature causes the production of fourth heart sound.
  • 9. ATRIAL DIASTOLE • After atrial systole, the atrial diastole starts. Simultaneously, • ventricular systole also starts. • Atrial diastole lasts for about 0.7 sec (accurate duration is 0.69 sec). • This long atrial diastole is necessary because, this is the period during which atrial filling takes place. • Right atrium receives deoxygenated blood from all over the body through superior and inferior venae cavae. • Left atrium receives oxygenated blood from lungs through pulmonary veins.
  • 10. Atrial Events Vs Ventricular Events
  • 12. ISOMETRIC CONTRACTION PERIOD • is the first phase of ventricular systole and lasts for 0.05 second • It is the type of muscular contraction characterized by increase in tension, without any change in the length of muscle fibers. • Isometric contraction of ventricular muscle is also called isovolumetric contraction. • Immediately after atrial systole, the atrioventricular valves are closed due to increase in ventricular pressure. • Semilunar valves are already closed. • ventricles contract as closed cavities, in such a way that there is no change in the volume of ventricular chambers or in the length of muscle fibers. • Only the tension increases in ventricular musculature. • Because of increased tension in ventricular musculature during isometric contraction • the pressure increases sharply inside the ventricles.
  • 13. ISOMETRIC CONTRACTION PERIOD First Heart Sound • Closure of atrioventricular valves at the beginning of this phase produces first heart sound. Significance of Isometric Contraction • The ventricular pressure increases greatly above the pressure in the aorta and pulmonary artery, the semilunar valves open. • Thus, the pressure rise in ventricle, caused by isometric contraction is responsible for the opening of semilunar valves, leading to ejection of blood from the ventricles into aorta and pulmonary artery.
  • 14. EJECTION PERIOD • Due to the opening of semilunar valves and isotonic contraction of ventricles, • blood is ejected out of both the ventricles. Hence, this period is called ejection period. • Duration of this period is 0.22 second. Ejection period is of two stages 1. First Stage or Rapid Ejection Period • starts immediately after the opening of semilunar valves. • large amount of blood is rapidly ejected from both the ventricles. • It lasts for 0.13 second. 2. Second Stage or Slow Ejection Period • the blood is ejected slowly with much less force. • Duration of this period is 0.09 second.
  • 15. EJECTION PERIOD End-systolic Volume • Ventricles are not emptied at the end of ejection period and some amount of blood remains in each ventricle. • Amount of blood remaining in ventricles at the end of ejection period (i.e. at the end of systole) is called endsystolic volume. • It is 60 to 80 mL per ventricle. • Measurement of end-diastolic volume End systolic volume is measured by radionuclide angiocardiography (multigated acquisition – MUGA scan) and echocardiography. • It is also measured by cardiac catheterization, computed tomography (CT) scan and magnetic resonance imaging (MRI) Ejection Fraction • refers to the fraction (or portion) of end diastolic volume that is ejected out by each ventricle per beat. • From 130 to 150 mL of end diastolic • volume, 70 mL is ejected out by each ventricle (stroke volume). • Normal ejection fraction is 60% to 65%.
  • 16. PROTODIASTOLE • is the first stage of ventricular diastole, • Duration of this period is 0.04 second. • Due to the ejection of blood, the pressure in aorta and pulmonary artery increases and pressure in ventricles drops. • When intraventricular pressure becomes less than the pressure in aorta and pulmonary artery, the semilunar valves close. • Atrioventricular valves are already closed • protodiastole indicates only the end of systole and beginning of diastole. Second Heart Sound • Closure of semilunar valves during this phase produces second heart sound
  • 17. ISOMETRIC RELAXATION PERIOD • is the type of muscular relaxation, characterized by decrease in tension without any change in the length of muscle fibers. • Isometric relaxation of ventricular muscle is also called isovolumetric relaxation • During isometric relaxation period, once again all the • valves of the heart are closed • both the ventricles relax as closed cavities without any change in volume or length of the muscle fiber. • Intraventricular pressure decreases during this period. • Duration of isometric relaxation period is 0.08 second. Significance of Isometric Relaxation • the ventricular pressure decreases greatly. When the ventricular pressure becomes less than the pressure in the atria, atrioventricular valves open. Thus, the fall in pressure in the ventricles, caused by isometric relaxation is responsible for the opening of atrioventricular valves, resulting in filling of ventricles.
  • 18. RAPID FILLING PHASE • When atrionventricular valves are opened, • sudden rush of blood (which is accumulated in atria during atrial diastole) from atria into ventricles. • This period is called the first rapid filling period. • Ventricles also relax isotonically. About 70% of filling takes place during this phase, which lasts for 0.11 second. Third Heart Sound • Rushing of blood into ventricles during this phase causes production of third heart sound.
  • 19. SLOW FILLING PHASE • After the sudden rush of blood, the ventricular filling becomes slow • It is also called diastasis. About 20% of filling occurs in this phase. • Duration of slow filling phase is 0.19 second. „LAST RAPID FILLING PHASE • Last rapid filling phase occurs because of atrial systole. • After slow filling period, the atria contract and push a small amount of blood into ventricles. • About 10% of ventricular filling takes place during this period. • Flow of additional amount of blood into ventricle due to atrial systole is called atrial kick. End-diastolic Volume • is the amount of blood remaining in each ventricle at the end of diastole. • It is about 130 to 150 mL per ventricle.
  • 21. ASSIGNMENT • Intra-atrial pressure changes during cardiac cycle • Intraventricular pressure changes during cardiac cycle