Cardiac Cycle Flashcards
(30 cards)
What is the cardiac cycle?
It is a sequence of alternating contraction & relaxation of the atria & ventricles to pump blood throughout the body.
What allows action potentials to spread directly from one myocyte to the next?
Gap Junctions
Where is the SA node located?
Near the opening of the SVC on the superior lateral wall of the right atrium
Where is the AV node located?
Medial & Posterior to the tricuspid valve
What is known as the pacemaker of the heart?
SA node
What happens in diastole?
The heart fills with blood
What happens in Systole?
The heart contracts to pump the blood
What is the first event of the cardiac cycle?
Atrial diastole
During atrial diastole, blood passively fills the right & left through what vessels?
Rightβ SVC & IVC
Leftβ Pulmonary Veins
When does blood leave the atrium to the ventricle?
When the pressure in the atrium exceeds that of the ventricle on the same side
What is isovolumetric relaxation?
It is a phase that occurs during ventricular diastole where there is no change in the amount of blood in the ventricle but thereβs a fall in the intra-ventricular pressure
What is rapid ventricular filling?
This occurs when the ventricular pressure becomes less than the atrial pressure and the AV valves open, leading to ventricular filling.
What is the end diastolic volume?
The total blood present in the ventricle at the end of diastole.
End diastolic vole is also called?
Pre-load
What are the phases of ventricular diastole?
First third of the diastolic phase (early ventricular diastole): ventricular rapid inflow.
Middle third of the diastolic phase (late ventricular diastole): passive inflow or diastasis.
Last third of the diastolic phase (atrial systole): ventricular filling due to atrial contraction (20%).
What is the longest phase of the cardiac cycle?
Diastasis
What is the longest phase of the cardiac cycle?
Diastasis
What is isovolumetric contraction?
It is the phase of the cardiac cycle in early systole where the ventricles contract with all heart valves closed, causing a rapid rise in pressure without any change in ventricular volume.
I.e at this phase the pressure in the ventricle is not enough to open the semi-lunar valves and the AV valves are also closed
What is the end systolic volume?
The volume of blood left in the ventricle at the end of systole.
It is usually between 40-50mls
What is another name for the end systolic volume?
After load
What is the value of the end systolic volume?
40-50 mls
What is the stroke volume output?
It is the amount of blood ejected from the ventricle
What is the ejection fraction?
It is the ratio of the stroke volume output to the end diastolic volume.
It is about 60%
What is the percentage of the ejection fraction?
60%
