CVS Physiology 3- The cardiac cycle Flashcards
What is the cardiac cycle?
The sequence of pressure and volume changes that takes place during cardiac activity
What are the mechanical events brought about by?
The rhythmic changes in cardiac electrical activity
The cardiac cycle consists of alternate periods of what?
Systole
Diastole
At rest, is diastole or systole longer in duration?
Diastole
What valves are known as the semilunar valves?
Aortic and pulmonary
When pressure is gretaer behind the valve, what happens?
Valve opens
When pressure is greater in front of the valve, what happen?
Valve closes
Does not open in opposite direction
What is an ECG a record of?
The overall spread of electrical activity through the heart
What can be described at mid-diastole?
Atrial and ventricular pressures low
Ventricles contain ~80% of final filled volume
Aortic and pulmonary valves closed
Aortic pressure high
What can be described at late diastole?
P wave of ECG occurs
Towards end of P wave atria contract- increasing arterial pressure-most of the blood in the atria is propelled into ventricles
Small increase in ventricular pressure
What can be described at End of diastole/early systole?
QRS complex of ECG begins- start of ventricular depolarisation
Ventricles contract at end of QRS complex- early systole
Rapid increase of ventricular pressure
During early systole, AV valves snap shut, this causes what?
First heart sound
Ventricles contrat but both AV and aortic valves are shut- noblood can enter or leave
What can be described at the ejection period?
Ventricular pressure exceeds arterial pressure - aortic and valve pulmonary valves open
Blood is ejected into the aorta and pulmonary artery
Aortic pressure rises
What can be desribed at the end of ventricular systole?
T wave signals ventricular depolarisation
Ventricles start to relax- ventricular pressure falls below aortic pressure-aortic valves shuts
What causes the second heart sound in the end of the ventricular systole?
When the aortic vlaves shut again
and Dicrotic notch (incisura) on aortic pressure record
What can be described at the filling period?
Ventricular pressure falls below atrial pressure
AV valves open
Major part of ventricular filling
blood which entered atria during ventricular systole is released into ventricles by opening of AV valves
Atrial and ventricular pressures fall sharply and ventricular volume increases rapidly
Name the 5 phases of the cardiac cycle and what ones are ventricular filling or ventricular emptying
Ventricular Filling:
- Passive filling during ventricular and atrial diastole
- Atrial contraction
- Isovolumetric ventricular contraction
Ventricular Emptying:
- Ventricular ejection
- Isovolumetric ventricular relaxation
How are the heart sounds generated?
Heart action
How can heart sounds be detected?
Phonocardiogram
What are the two distinct heart sounds?
1st-Coincides with the begining of systole- produced bby the closure of the AV valves
2nd-Begins with the onset of diastole-closure of the aortic and pulmonary (semilunar) valves
What are abnormal sounds in pathological conditions called?
Murmurs
