Cardiovascular Physiology: Atrial Systole and Isovolumetric Contraction

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Questions and Answers

What percentage of ventricular filling is caused by atrial contraction?

40%

30%

20% (correct)

10%

What is the cause of the 'a' wave on the Wiggers Diagram?

Ventricular depolarization

Atrial contraction (correct)

Atrial depolarization

Ventricular contraction

What is the name of the phase of systole where the ventricles contract and the AV valves close, but there is no change in volume?

Atrial diastole

Isovolumic contraction (correct)

Ventricular ejection

Rapid ejection

What is the name of the complex on the Electrocardiogram that represents ventricular depolarization?

QRS complex Signup and view all the answers

What is the result of the slight backflow of blood into the atria at the onset of ventricular contraction?

Atrial c wave Signup and view all the answers

What is the increase in LA pressure during atrial contraction?

7-8 mmHg Signup and view all the answers

What is the phase of the cardiac cycle where the atria contract and add additional filling to the ventricles?

Atrial systole Signup and view all the answers

What is the purpose of the Wiggers Diagram?

To display the cardiac cycle Signup and view all the answers

What is the minimum pressure required to open the aortic valve?

80 mm Hg Signup and view all the answers

What phase of the cardiac cycle is characterized by a decrease in ventricular volume and an increase in aortic pressure?

Ejection phase Signup and view all the answers

What is the name of the wave that occurs in the atria at the end of ventricular contraction and beginning of relaxation?

Atrial v wave Signup and view all the answers

When does the aortic valve close?

At the end of the T wave Signup and view all the answers

What is the name of the phase of the cardiac cycle that begins when the ventricles start to relax?

Diastole Signup and view all the answers

What happens to the ventricular volume during the isovolumetric relaxation phase?

It remains constant Signup and view all the answers

What occurs when the aortic valve closes during the cardiac cycle?

An incisura occurs, followed by a short period of backward flow of blood Signup and view all the answers

During which phase of ventricular diastole does the atrioventricular valve open and blood flows rapidly from the atria to the ventricles?

Rapid filling phase Signup and view all the answers

What is the name of the diagram that illustrates the cardiac cycle phases?

Wiggers Diagram Signup and view all the answers

What is the approximate aortic pressure at the end of diastole?

80 mmHg Signup and view all the answers

What is the significance of the T wave in the cardiac cycle?

It represents ventricular repolarization Signup and view all the answers

What is the term for the period of slow filling of the ventricles during diastole, characterized by a small increase in ventricular volume?

Diastasis Signup and view all the answers

During which phase of the cardiac cycle does the atrial contraction occur?

Late diastole Signup and view all the answers

What is the term for the volume of blood in the ventricle at the end of diastole?

End diastolic volume (EDV) Signup and view all the answers

What is the formula for calculating stroke volume?

SV = EDV - ESV Signup and view all the answers

What is the name of the diagram that illustrates the different phases of the cardiac cycle?

Wiggers Diagram Signup and view all the answers

Study Notes

Atrial Systole

The atria starts contraction after atrial depolarization, around the middle of the P wave.
Atrial contraction causes additional 20% filling of the ventricles.
"a" wave is caused by atrial contraction, resulting in an increase in LA pressure by about 7-8 mmHg.
Ventricular pressure and volume increase due to atrial contraction and blood injection.

Isovolumetric Contraction

After atrial contraction, the ventricles start to contract.
This is the 1st phase of systole: isovolumic contraction.
LV pressure curve increases, and AV valves close (S1).
No volume change occurs during this phase.
This phase occurs around the middle of the QRS complex, which represents ventricular depolarization.

Atrial C Wave

Atrial c wave occurs when ventricles begin to contract, resulting in slight backflow of blood into the atria.
This wave is mainly caused by the closing of the AV valves.

Diastole

When the aortic valve closes, an incisura (dichroic notch) occurs, resulting in a short period of backward flow of blood.
Aortic pressure then decreases slowly throughout diastole.
Blood flows continually through peripheral vessels during this phase.
Before ventricle contraction, aortic pressure is around 80 mmHg (diastolic pressure).

Rapid Filling

When pressure decreases in the ventricle, the AV valve opens, and blood flows rapidly from the atria to the ventricles.
Ventricular volume curve increases during this phase.
This is the 2nd phase of ventricular diastole: rapid filling.

Diastasis

In the middle third of diastole, only a small amount of blood flows into the ventricles.
Ventricular volume curve slightly increases during this phase.
This is the 3rd phase of ventricular diastole: diastasis.
Diastasis persists until the SA node initiates an AP, leading to atrial contraction.

Atrial Systole (Again)

In the last third of diastole (4th phase), the atria contract again, and another cycle begins.

Volumes

End-diastolic volume (EDV) and end-systolic volume (ESV) are important measurements.
Stroke volume (SV) is calculated as EDV - ESV.

Ventricular Ejection

As soon as the pressure is high enough to overcome the pressure inside the aorta (80 mmHg), the aortic valve opens, and blood is pumped out of the LV.
This is the 2nd phase of systole: ejection phase.
Ventricular volume curve decreases, and aortic pressure curve increases to about 120 mmHg (systolic pressure).

Atrial V Wave

Atrial v wave occurs in the end of ventricular contraction and beginning of relaxation.
This wave results from slow flow of blood into the atria from veins while A-V valves are closed.

Isovolumetric Relaxation

Then suddenly, the ventricles start to relax (diastole begins) at the end of the T wave, which represents ventricular repolarization.
Ventricular pressure curve decreases, and aortic valve closes (S2).
When AV and SL valves are closed, no change in ventricular volume occurs (isovolumetric).
This is the 1st phase of ventricular diastole.

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Description

Learn about the atrial systole and isovolumetric contraction phases of the cardiac cycle, including atrial depolarization, ventricular filling, and pressure changes.