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Associated Prof. of physiology

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Presentation on theme: "Associated Prof. of physiology"— Presentation transcript:

1 Associated Prof. of physiology
Cardiac cycle By Dr. Enas Albendary. References Guton& Hall 11th ed. Ganong. Several Websites Associated Prof. of physiology Dr. Enas (2009)

2 Objectives Cardiac Cycle Definition Phases
Events, their names & duration Pressure changes Atria Ventricles Aorta Volume changes ECG & Cardiac Cycle Heart Sounds & Cardiac Cycle Dr. Enas (2009)

3 Cardiac Cycle It is the cardiac events that occur from the beginning of one heart beat to the beginning of the next one. Dr. Enas (2009)

4 Heart acts as a dual pump
The cardiac cycle consists of one systole-diastole sequence of the heart,& it lasts about 0.8 sec. It starts by atrial systole (contraction). Followed by ventricular systole then diastole (relaxation) of the whole heart. Dr. Enas (2009)

5 ‘Heart’ Dual Pump Dr. Enas (2009)

6 What is the meaning of Systole and Diastole Dr. Enas (2009)

7 Phases of Cardiac Cycle
There are seven (7) phases of cardiac cycle: 1- Atrial systole.(0.1 second). Ventricular Systole: divided into 3 phases:- 2- Isovolumetric ventricular contraction.(0.05 sec.). 3- Rapid ventricular ejection.(0.15 sec.). 4- Reduced ventricular ejection.(0.1 sec.). Ventricular Diastole: divided into 3 phases:- 5- Isovolumetric ventricular relaxation.(0.06 sec.). 6- Rapid ventricular filling. (0.1 sec.). 7- Reduced ventricular filling (diastasis) (0.2 sec.). Dr. Enas (2009)

8 Phases of Cardiac Cycle
Dr. Enas (2009)

9 1- Atrial Systole In this phase , both atria contract leading to blood evacuation into the ventricles. 1- Atrial pressure:- This initially increases (due to reduction of arterial volume,then decrease again due to evacuation of blood into corresponding ventricle. 2- Ventricular pressure:- This initially increase slightly (due to entry of blood) then drop due to ventricular dilation. 3- Ventricular volume:- Increase slightly due to ventricular dilation. 4- Valves: A-V valves are open while seilunar valves are closed. 5- Aortic Pressure:-Decrease gradually due to continuous blood flow from the aorta to the periphery. 6- Heart sounds: 4th heart sound is recorded in this phase. 7- ECG :- P wave start about 0.02 before this phase . While main P wave,P-R segment & Q wave occure during it. Dr. Enas (2009)

10 2- Isometric (Isovolumetric) ventricular contraction phase
This is the early phase of vent. systole in which the ventricle contract but not ejection occurs. Its events include the following :- Ventricular pressure & volume: The ventricles contract isometrically i.e. without shortening of the cardiac muscle .So vent. pressure rises sharply while vent. Volume remain constant Valves: Vent. Press. Become greater than atrial press. Causes closure of A-V valves producing 1st heart sound while semi lunar valves are still closed. Sound: 1st heart sound due to sudden closure of A-V valves Atrial pressure: slightly increased due to bulging of A-V cusps into the atria. Aortic pressure: this decrease to a minimum of about 80 mmHg at the end of this phase (diastolic blood pressure). ECG: The Q wave starts about 0.02 second before this phase, while the R &S waves occur during it. Dr. Enas (2009)

11 3- Rapid ventricular ejection phase:
In this phase, the semilunar valves open &blood is ejected into the great arteries. Its events include : Ventricular volume & pressure : vent. Contract isotonically (i.e cardiac musc. Fibers are shortened) .So vent. Volume is rapidly decreased while its pressure is markedly increased to maximum 120 mmHg. Valves: A-V valve are still closed while semilunar valve. Will open b/c vent. Press. Will exceed aortic press. Sound: continuation of 1st heart sound. Atrial pressure: decreased b/c its widening of its cavity then increase due to its filling by venous return. Aortic pressure: is markedly increased due to ejection of blood to it & reach maxim.120mmHg.(systolic blood pressure) ECG: The S-T segment is present in this phase and T wave start in its late part. Dr. Enas (2009)

12 4- Reduced ventricular ejection phase:
The event in this phase are a continuation of those occurring in the preceding phase: Ventricular volume:- this is further decreased. Ventricular pressure:- This is slightly decreased due to ejection of most blood in preceding phase Aortic pressure:- is slightly decreased. Valves: still the semilunar valve are open &the AV valves closed. Sound: there are no sound in this phase. Atrial pressure: this is still increasing due to venous return. ECG: this show most of the ascending limb and the top of the T wave. Dr. Enas (2009)

13 5- Isovolumetric ventricular relaxation phase:
This is the early phase of ventricular distole in W’ventricles relax but no filling occurs. Its events include : Ventricular volume:- remains unchanged Ventricular pressure:- falls sharply (to 0- 5mmHg.) Aortic pressure:- is initially increase (due to elastic recoil of aorta ) then gradually decrease due to continuous flow of blood to peripheral arteries. Valves:- Semilunar valves are suddenly closed & A-V valve is still closed. Sound: the 2nd heart sound Atrial pressure: this is still increasing due to continuous venous return. ECG: most of the descending limb of the T wave is present in this phase. Dr. Enas (2009)

14 6- Rapid ventricular filling phase:-
In this is phase, the atrial pressure exceeds the ventricular pressure, so the AV valve open and rapid filling of the ventricles. Its events include : Ventricular volume & pressure: there is initial decrease in pressure due to vent. Relaxation then increase markedly while volume is increased gradually Atrial pressure: initial increase due to rush of blood into ventricles then increase due to venous return. Aortic pressure: still decrease due to continuous flow of blood to the periphery. Valves: the Sound: the 3rd heart sound. ECG: the early of the T-P segment and the U wave are present in this phase. Dr. Enas (2009)

15 7- slow ventricular filling phase:
In this is phase, Its events include : Ventricular volume & pressure: these still gradually increase but at a slower rate. Atrial pressure: this is still increasing due to venous return. Aortic pressure: this is still decreasing due to continuouse blood flow from the aortic to the peripheral arteries. Valves: the AV valves are open while the semilunar valve are closed. Sound: there are no sound in this phase. ECG: the late part of the T-P segment and the start of the P wave are present in this phase. Dr. Enas (2009)

16 Changes in ventricular pressure& volume in systole& diastole
Dr. Enas (2009)

17 Dr. Enas (2009)

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