The cardiac cycle Flashcards
What will be investigated while studying the cardiac cycle?
- The electrical activity
- ECG and AP
- Mechanical properties
- Stages of valve motion
- Pressure and volume circumstances in the chambers
- sound phenomena
What is the cardiac cycle composed of?
the cadiac cycle is an uninterruptedly repeated process of the heart
consists of two elements:
- systole
- diastole
What does it mean that the systole and diastole do not fully separate in time?
- The systole of the atria appears at the end of the diastole of the ventricles.
- this makes it possible that close to the end of the ventricular diastole a further fraction of blood can enter the ventricles.
Explain systole:
- During the course of systole the heart displays considerable deformation.
- Under real circumstances the systole is preceded by a twisting movement of the heart musculature followed by a considerable shift of the heart towards the base and back towards the apex.
- emptying of the ventricles.
Explaind Diastole:
- relaxation
- the filling during diastole from the direction of the hollow veins causes characteristic deformations as well.
What are the most important parameters of cardiac functions?
- aortic pressure
- arterial pressure
- ventricular pressure
- ventricular volume
- ECG
- heart sounds
Atrial contraction; Phase 1
Cuspidal valves are open: Semilunar valves are closed.
- Atrial contraction phase begins after the P-wave (atrial depolarization).
- The atrial wall is contracted, therefore pressure in the lumen increases.
- This pumps extra amount of blood into the ventricles through the open cuspidal valves.
- The ventricular muscle is entirely relaxed.
- Aortal blood pressure decreases.
Isovolumetric contraction; Phase 2
All valves are open
- Begins with the QRS complex of the ECG trace (ventricular depolarization)
- Ventricular volume is unchanged, but stretch of the wall is constantly increasing.
- The increased wall tension elevates the pressure in the ventricle, thus cuspidal valves are closed in this phase.
- Ventricular pressure elevates until it reaches the aortic (and tr. pulmonalis) pressure = end of this phase.
Rapid ejection; Phase 3
Semilunar valves are open, cuspidal valves remain closed
- after the previos phase, semilunar valves open (ventriculare pressure is higher than aortic and tr.pulmonalis). Isometric contraction begins.
= ejection
A major volume of the blood will be put into the aorta and tr. pulmonalis. The extra amount of blood will increase the aortic pressure
Reduced ejetion; Phase 4
Semilunar valves are open, Cuspidal valves remain closed
Isovolumetric relaxation; Phase 5
All valves are closed
- Due to the relaxation, ventricular pressure drops under the aortic and truncus pulmonalis pressure, at this point semilunar valves will close.
- in the first phase of relaxation, all valves are closed, thus no blood flow occurs in the heart. This is called isovolumetric relaxation.
- till the end of this phase semilunar valves are closed.
Rapid filling; Phase 6:
Semilunar valves open (cuspidal valves open??)
- the ventricular pressure is further dropping, and when it gets under the atrial pressure, cuspidal valves will open. At this point rapid ventriuclar filling begins.
- Semilunar valves are closed, but due to the elastic components of the aorta, the blood flos further into the arterial system ( aortic pressure decreases)
- the major volume of the blood flows into the ventricles in this phase.
Reduced filling; Phase 7
Semilunar valves are open (cuspidal valves are open??)
- Cuspidal valves are still open, ventricular muscle cells are relaxed.
- mor blood flows passively into the ventricles form the atria.
- Semilunar valves are closed, but blood from the aorta flows into the arterial system (elastic components). Aortic pressure drops.
What is heart sounds generated by?
The closing of valves
1st heart sound is:
Systolic, during closure of cuspid valves
elements:
- Vibration of contracted muscle
- Turbulence due to closure of cuspid valves
- Turbulence due to fast ejection
