Name the cardiac pacemakers from fastest to slowest
Sinus-atrial (SA) node
Atrio-ventricular (AV) node
What is another name for the pacemaker current?
Is the conduction from the to AV fast or slow?
The conduction is via the atrial muscle and it's slow
Is conduction through the AV node fast or slow? reason??
The conduction is slow 'AV pause'
• This allows atrial filling to occur before passing on the electrical impulse
• It also prevents transmission of high rates from the atria
Is the conduction through the ventricular ‘conduction system’ fast or slow? reason ?
It's fast. It allows the apex to contract before the base
What is an ECG?
An electrocardiogram (ECG) is a medical test that detects cardiac (heart) abnormalities by measuring the electrical activity generated by the heart as it contracts. The machine that records the patient's ECG is called an electrocardiograph.
P: atrial depolarisation
Q: depolarisation of the septum(towards the atria)
R: Depolarisation of the ventricles (towards the apex)
S: Depolarisation of the ventricles (towards the atria)
T: Repolarisation of the ventricles (towards the endocardium)
How many valves are there and what are they called?
4 Aortic Valve (semilunar) Tricuspid valve (right AV) Pulmonary valve (semilunar) Mitral valve (Bicuspid/Left AV)
The cardiac conduction system?
Conduction from SA to AV nodes is via the atrial muscle and is slow
Conduction through the AV node is slow – ‘AV pause’
- this allows atrial filling to occur before passing on the electrical impulse
- it also prevents transmission of high rates from the atria
Conduction through the ventrcular ‘conduction system’ is fast
This allows the apex to contract before the ‘base’
explain Pressure-Volume (P-V) Loops
and label the diagram
Explain the cardiac cycle (step 1 and 2)
1. left atrial pressure higher than LV pressure
Mitral valve opens
Blood flows into LV
2. Left atrium contracts
- gives atria kick
Explain the cardiac cycle (steps 3, 4 5 and 6)
3. Left ventricle contracts
4. Left ventricular 100 pressure rises
5. Aortic valve opens when ventricular pressure exceeds aortic pressure
Explain the cardiac cycle (steps 7, 8, 9 and 10)
7. End-systolic pressure falls
8. LV pressure falls below 100 aortic pressure and aortic valve shuts 80
9. Period of isovolumic relaxation
10. LV pressure falls below atrial pressure and mitral valve opens and ventricle refills