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The Circulatory System. The Heart. Lecture # 4. (Chapter 19). Blood Flow, Heart Sounds, and Cardiac Cycle Cardiac Output. The Heart. Gas exchange. Poor oxygen blood. Gas exchange. Superior vena cava . Pulmonary arteries. Coronary sinus. Reach oxygen blood. Pulmonary veins.
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The Circulatory System The Heart Lecture # 4 (Chapter 19) • Blood Flow, Heart Sounds, and Cardiac Cycle • Cardiac Output
The Heart Gas exchange Poor oxygen blood Gas exchange Superior vena cava Pulmonary arteries Coronary sinus Reach oxygen blood Pulmonary veins Inferior vena cava RIGHT ATRIUM LEFT ATRIUM To the rest of the body Aorta TISSUES RIGHT VENTRICLE LEFT VENTRICLE
Superior vena cava Heart Sounds During ventricular systole (contraction) the two AV close at the same time and produce the first sound referred aslubb. Pulmonary veins (4) Coronary sinus Lubb Pressure Pressure Lubb Inferior vena cava
Superior vena cava Heart Sounds Pulmonary veins (4) Coronary sinus Dupp Pressure Pressure Dupp When the ventricles relax (diastole) the two semilunar valves close at the same time and produce the second sound referred asdubb. Inferior vena cava
The Cardiac Cycle At the beginning of their contraction (systole) the ventricles contracts isovolumetrically (the pressure increases but the volume inside the ventricles does not changes). In the period of isovolumetric contraction, the ventricles contract and the pressure rises, but blood does not flow because all the valves are closed. Pressure Pressure
The Cardiac Cycle Pressure Pressure Once pressure in the ventricles exceeds that in the arterial trunks (pulmonary and aortic), the semilunar valves open and blood flows into the pulmonary and aortic trunks. This point marks the beginning of the period of ventricular ejection.
(b) At the start of the atrial systole, the ventricles are already filled to about 70% of their normal capacity, due to passive blood flow. At the end of the atrial systole, each ventricle contains a maximum amount of130 mL of blood: End-diastolic volume (a) (c) 1- Ventricular Filling In the period of isovolumetric contraction, the ventricles contract and the pressure rises, but blood does not flow because all the valves are closed. 2- Isovolumetric Contraction (d) (e) This point marks the beginning of the period of ventricular ejection. 4- Isovolumetric Relaxation 3- Ventricular Ejection
(f) At the start of the atrial systole, the ventricles are already filled to about 70% of their normal capacity, due to passive blood flow. (a) Atrial Systole A small amount of blood (30 %) is forced to the ventricles Ventricular contraction closes the AV valves (first sound). Isometric contraction. First Phase: Ventricular Systole Pressure increases and semilunar valves open. Ventricular ejection. Second Phase: Early: Pressure decreases in the ventricles and semi-lunar valves close (second sound). Ventricular Diastole Atria are also in diastole. Passive blood flow fills the ventricles (70%). Late: Ventricles are also in diastole. Passive blood flow fills the ventricles (70%). Atrial Diastole
Phases of the Cardiac Cycle 2 Isovolumetric contraction 3 Ventricular ejection 4 Isovolumetric relaxation 1a- Rapid filling 1- Ventricular filling 1c- Atrial systole 1b- Diastasis QRS T P The elastic recoil and expansion would cause pressure to drop rapidly and suck blood into the ventricles During diastole, ventricles expand, their pressure drops below that of the atria, AV valves open and blood flows into the ventricles Ventricles depolarize, create the QRS complex, and begin to contract Ejection of blood begins when the ventricular pressure exceeds arterial pressure and forces semilunar valves open AV valves close as ventricular blood surges back against the cusps • 1a- Rapid ventricular filling, first one-third, blood enters very quickly • 1c- Atrial systole, final one-third. Atria contract • Blood from the aorta and pulmonary briefly flows backwards • filling the semilunar valves and closing the cusps. Heart sound S2 occurs The stroke volume (SV) of about 70 mL of blood is ejected of the 130 mL in each ventricle Heart sound S1 occurs at the beginning of this phase • 1b- Diastasis, second one-third, marked by slower filling. P wave occurs at the end of diastasis Each ventricle contains 130 mL of blood: End-diastolic volume It is ‘isovolumetric’ because even though the ventricles contract, they do not eject blood • The ejection fraction is about 54% (as high as 90% in vigorous exercise) End-systolic volume (ESV) 60 mL of blood left behind
Events of the Cardiac Cycle • ventricular filling • isovolumetric contraction • ventricular ejection • isovolumetric relaxation
End-diastolic volume (EDV) It is the volume of blood that each ventricle contains at the end of ventricular filling (about 130 mL). Stroke volume (SV) It is the volume of blood that each ventricle ejects during ventricular ejection (about 70 mL). Ejection fraction It is the percentage of the end-diastolic volume that is ejected: 70/130 x 100= 53.8 % (about 54%). In vigorous exercise the ejection fraction may be as high as 90% The ejection fraction is an important measure of cardiac health. A diseased heart may eject much less than 50% of the blood it contains. End-systolic volume (ESV) It is the volume of blood left behind in the ventricles after ventricular ejection. (ESV) EDV – SV =
