Cardiac Cycle Flashcards
When do heart valves produce a sound?
When they shut NOT when they open
Explain an overview of the cardiac cycle?
The orderly depolarization and repolarization sequence triggers a recurring cardiac cycle of atrial and ventricular contractions and relaxations
Diastole. what happens?
The hearts ventricles are relaxed and fill with blood
Systole. What happens?
The heart ventricles contract and pump blood into the aorta and pulmonary artery
Events during the cardiac cycle?
Passive Filling Atrial contraction Isovolumetric ventricular contraction Ventricular ejection Isovolumeteric ventricular relaxation
Isovolumetric?
no corresponding volume change- ventricular volume does not change because all valves are closed at this time
What is the pressure in the atria and ventricles during the passive filling stage?
Close to 0
What occurs in the passive filling stage?
AV valves open so venous return flows into the ventricles
What is the aortic pressure during passive filling?
~80mmHg
The aortic valve is closed during passive filling. True or False?
True it is closed
How full do ventricles become by filling?
80% full
What happens in the right side of the heart during passive filling?
Basically the same as the left except the pressures (right ventricular and pulmonary artery) are much lower
Explain the valves in passive filling?
Aortic valve is closed Mitral is open Pulmonary is closed Tricuspid is open
What does the P wave in an ECG signal?
Atrial depolarization
When does the atria contract on an ECG?
Between the P wave and the QRS
What does atrial contraction achieve?
The end diastolic volume
When does ventricular contraction start?
After the QRS wave on an ECG
What happens in Isovolumeteric contraction?
Ventricular pressure rises- when it exceeds atrial pressure the AV valves ShUt Producing the first LUB sound Aortic valve is still shut so no blood can enter or leave ventricles yet - Ventricular pressure rises very steeply- the tension is rising around a closed volume
What happens when ventricular pressure exceeds atrial pressure?
The AV valves shut
Why is it called isovolumeteric?
The tension is rising around a closed volume
Explain the pressures in ventricular ejection?
When the ventricular pressure exceeds aorta/pulmonary artery pressure
What happens in ventricular ejection?
Ventricular pressure exceeds pressure in aorta/pulmonary artery. Aortic/pulmonary valve opens (silently) Stroke volume is ejected by each ventricle leaving behind the end systolic volume. Aortic pressure rises
What does ventricular ejection leave behind?
End Systolic volume
SV and end volumes equation?
SV= EDV- ESV
What does the T wave in an ECG represent?
Ventricular repolarization
What happens in ventricular repolarization (part of VE)
Ventricles relax and ventricular pressure starts to fall When V pressure falls below aortic/pulmonary pressure- aortic pulmonary valves shut Producing the second heart beat DUB
What produces the DUB sound?
When ventricular pressure falls below that of aortic/pulmonary and the aortic and pulmonary valve shut
What does valve vibration produce in an aortic pressure curve?
Dicrotic notch
What happens in isovolumeteric ventricular relaxation?
Closure of aortic/pulmonary valves signal the start of this time AV valve is shut so therefore ventricle is closed box Tension falls around a closed volume
What happens when ventricular pressure falls below atrial pressure?
AV valves open Heart starts a new cycle
What is the first heart sound called and caused by?
S1 Caused by closure of mitral and bicuspid valves
What does S1 indicate?
The start of systole
What is the second heart sound called and caused by?
S2 Closure of aortic and pulmonary valves
What does S2 indicate?
The end of systole and beginning of diastole
How does arterial pressure not reach 0 in diastole?
Pressure from external environment?
When does JVP occur?
After right atrial pressure waves
What does JVP stand for?
Jugular venous pressure
Diagram showing relative heart pressures during cariac cycle?
Explain this diagram?
This is a JVP diagram to show it happens after right atrial pressure waves
a is atrial contraction
c bulging of tricuspid valve into atrium during ventricular contraction
v is a rise of atrial pressure during atrial filling
