Sesh 2: Electrical activity of the heart Flashcards
What cells set the HR?
Automaticity of pacemaker cells in SAN.
With increased HR, does diastole or systole shorten?
Diastole…systole remains the same
Roughly how long is the atrio-ventricular delay, and what does this allow?
~ 120ms to allow time for ventricles to finish filling.
What are the 7 phases of the cardiac cycle?
- Atrial contraction
- Isovolumetric contraction
- Rapid ejection
- Reduced ejection
- Isovolumetric relaxation
- Rapid filling
- Reduced filling
What are the approximate lengths of systole and diastole in seconds?
Systole= 0.35 s Diastole= 0.55 s
What does the P wave represent?
Atrial depolarisation
How much does atrial contraction contribute to ventricular filling?
The final 10%…most ventricular filling is passive.
What are the typical values for end- diastolic and end-systolic volume?
EDV= 120mL ESV= 40 mL
What does the QRS complex on an ECG signify?
Ventricular depolarisation
What causes the heart sounds S1, and S2?
S1= closure of mitral and tricuspid valves S2= closure of aortic and pulmonary valves
What does the T wave of the ECG signify?
Ventricular repolarisation
How do you calculate stroke volume?
EDV-ESV
When would you hear an aortic stenosis murmur?
Systole
When would you hear a mitral regurgitation murmur?
Systole
When would you hear a mitral stenosis murmur?
Diastole
