The Heart As a Pump Flashcards
Define Systole and Diastole
What is the typical pressure of the Aorta
Systole: Contraction and ejection of blood from ventricles
Diastole: Relaxation and filling of ventricles
Aorta- 120 systole/ 80 diastole
Define Stroke Volume
What is the typical SV of a 70kg man
What is the typical Cardiac Output for the same man
SV: Volume of blood ejected from heart per beat
Typical SV- 70ml per beat
Typical CO- 4.9 litres of blood per minute
How are cardia cells linked together?
What is the duration of a cardiac Action Potential?
Linked in a Functional Synctium
280ms- Duration of a single contraction
What are the 5. steps of the Conduction System
- Pacemaker in SA Node generate an AP
- Activity spreads over atria- Atrial Systole
- Reaches Atrioventricular Node and delayed for 120ms
- Excitation spreads down septum and through ventricular myocardium from endocardial to epicardial surface
- Ventricle contracts from apex up
What are the phases of the Cardiac Cycle
- Atrial Contraction
- Isovolumetric Contraction
- Rapid Ejection
- Reduced Ejection
- Isovolumetric Relaxation
- Rapid Filling
- Reduced Filling
At rest, what is the total duration of the cardiac cycle?
How much is Diastole, How much is Systole?
How are these 2 affected by exercise
Total= 0.9 seconds Diastole= 0.55 seconds Systole= 0.35 seconds
With Exercise;
Diastole decreases, Systole is constant
Where do we usually start from at Time=0 in a Wiggers diagram
In this phase;
Explain the Pressure change
Explain the Volume Change
Explain the ECG seen
Which valves are open and closed
Atrial Contraction
- Atrial pressure rises (Atrial Systole)—-> A wave
- Atrial contraction account for final 10% of ventricular filling
- Atrial depolarisation-> P wave in ECG
Open: Mitral/ Tricuspid
Closed: Aortic/ Pumonary
When are ventricular volumes maximal?
What is this called?
At end of Phase 1 (Atrial Contraction)
Termed: End-Diastolic Volume (EDV)
In Phase 2 of cardiac cycle,
Explain Pressure and Valve change
Explain Volume change
Explain the ECG seen
Explain what is heard
- Ventricle contraction so pressure rises
Mitral valve closes, producing C wave in Atrial Pressure curve - No volume changed as all valves closed
- Ventricular depolarisation shown by QRS complex on ECG
- Closure of Mitral and Tricuspid valve-> 1st heart sound S1
In phase 3 of cardiac cycle,
Explain the pressure and valve change
Explain the volume change
- Ventricular > Aortic pressure so aortic valve opens
- As ventricle contracts, atrial base pulled down so atrial pressure INITIALLY decreases. This is the X descent
- Decrease in ventricular volume, as blood ejected into aorta
In phase 4 of cardiac cycle,
Explain rate of ejection
Explain atrial pressure
Explain ECG Visible
- Ventricle repolarisation-> Decrese in tension and ejection rate decreases
- Atrial pressure rises as blood entering from lungs ( V Wave)
- Ventricular repolarisation-> T wave
In phase 5 of cardiac cycle,
Explain Pressure and Valve change
Explain the sound that is heard
- Rapid decline in ventricle pressure-> Brief backflow of blood into ventricle from Aorta, so aortic valve closes-> Dicrotic Notch in aortic pressure curve
- Closure of aortic and pulmonary valves-> 2nd heart sound S2
In phase 6 of cardiac cycle,
Explain Pressure and valve change
Explain sound heard
ventricle pressure< Atrial pressure
Mitral valve opens so ventricle fills with blood
Fall in atrial pressure after mitral valve opens is called Y-descent
3rd heart sound, S3 is due to ventricular filling which is normally silent
In phase 7 of cardiac cycle,
Explain the rate of filling of ventricle
Rate of filling slows down, as ventricle reaches its fixed volume.
What are 2 ways valves can function abnormally
Which side do most heart problems occur? Why?
Stenosis->Valve doesn’t open enough-> Blood flow obstructed
Regurgitation-> Valve does’t close all the way-> Back leakage
Left side due to higher pressure
