Cardiac cycle Flashcards

1
Q

What is a cardiac cycle?

A

All events that occur from the beginning of one heart beat to the beginning of the next

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What occurs during diastole and systole?

A
  • Diastole: the heart ventricles are relaxed and fill with blood
  • Systole: the heart ventricles contract and pump blood into the: aorta (LV) and pulmonary artery (RV)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

At a heart rate of 75bpm, how long does both the diastole and systolic phase last?

A

diastole = 0.5sec
systole= 0.3 sec
so diastole lasts almost twice as long as systole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 5 events during the cardiac cycle?

A
  • Passive Filling
  • Atrial Contraction
  • Isovolumetric ventricular Contraction
  • Ventricular Ejection
  • Isovolumetric ventricular Relaxation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe passive filling.

A
  • Pressure in atria and ventricles close to zero
  • AV valves open so venous return flows into the ventricles
  • Aortic pressure ~ 80 mmHg, and aortic valve is closed
  • Similar events happen in the right side of the heart, but the pressures (right ventricular and pulmonary artery) are much lower
  • Ventricles become ~ 80% full by passive filling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is atrial contraction ?

A

Completes the end diastolic volume and is represented in the ECG between the P-wave (atrial depolarisation) and the QRS wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe isovolumetric ventricular contraction.

A
  • Ventricular contraction starts after the QRS (signals ventricular depolarization) in the ECG
  • Ventricular pressure rises
  • When the ventricular pressure exceeds atrial pressure the AV VALVES SHUT
  • This produces the FIRST HEART SOUND (LUB)
  • The aortic valve is still shut, so no blood can enter or leave the ventricle
  • The tension rises around a closed volume “Isovolumetric Contraction”
  • The ventricular pressure rises very steeply
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What produces the first heart sound?

A

The “LUB” is produced by the closure of mitral and tricupsid valves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe ventricular ejection?

A

-When the ventricular pressure exceeds aorta/pulmonary artery pressure
-Aortic/pulmonary valve open - Remember this is a silent event
-Stroke Volume (SV) is ejected by each ventricle, leaving behind the End Systolic Volume (ESV)
-SV = EDV – ESV
= 135 – 65 = 70 ml
-Aortic pressure rises
-The T-wave in the ECG signals ventricular repolarization
-The ventricles relax and the ventricular pressure start to fall
-When the ventricular pressure falls below aortic/pulmonary pressure: aortic/pulmonary valves shut
-This produces the SECOND HEART SOUND (DUB)
-The valve vibration produces the dicrotic notch in aortic pressure curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What produces the second heart sound?

A

The “DUB” sound -When ventricular pressure falls below aortic/pulmonary pressure , the aortic/pulmonary valves shut

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the isovolumetric ventricular relaxation ?

A
  • Closure of aortic/and pulmonary valves signals the start of the isovolumetric ventricular relaxation
  • Ventricle is again a closed box, as the AV valve is shut
  • The tension falls around a closed volume “Isovolumetric Relaxation”
  • When the ventricular pressure falls below atrial pressure, AV valves open (Remember this is a silent event), and the heart starts a new cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why does arterial pressure does not fall to 0?

A

Due to elastic properties of arteries , they stretch when contracted and when they recoil so recoiling moves blood forward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

When does jugular venous pulse occur?

A

Occurs after right atrial pressure waves (indirect measurement ofd central venous pressure )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly