Flashcards in Session 2 Deck (19):
What valve separates the left atrium and ventricle?
The mitral valve
What are the features of cardiac muscle cells?
Straitions; branching; centrally positioned nuclei; intercalated discs joining cells; T-tubules inline with Z bands not the A-I band junction
What is systole?
The period where the heart is contracting
What is diastole?
The period of relaxation between heart contractions
How is ventricular muscle organised and why?
Organised in figure-of-eight bands to contract the ventricular chamber in the most effective way to maximise blood flow
What are the main differences between the left and right heart?
Left heart has thicker myocardium; right heart contains the main pacemaker (the SA node)
What occurs in the rapid filling phase of the cardiac cycle?
- Ventricular mass relaxes
- Intraventricular pressure falls below atrial pressure so the atrial and pulmonary valves close
- Tricuspid and mitral valves open
- Blood flows rapidly into the ventricles from the atria
What happens in the atrial contraction phase of the cardiac cycle?
- Atrial systole causes atrial pressure to rise
- Blood flows into the ventricles to reach end-diastolic volume (EDV)
What happens in the isovolumetric contraction phase of the cardiac cycle?
- Mitral valve closes as Intraventricular pressure exceeds atrial pressure
- Ventricle begins to contract so ventricular pressure rapidly rises
- All valves are closed so changes are isovolumetric
- Closure of the mitral valve generates the first heart sound (S1)
What happens in the rapid ejection stage of the cardiac cycle?
- Intraventricular pressure exceeds aortic pressure so aortic valve opens
- Rapid decrease in ventricular volume and pressure
- Atrial pressure decreases initially when the atrial base is pulled down in ventricular contraction
What happens in the reduced ejection phase of the cardiac cycle?
- Repolarisation of the ventricle causes a decline in tension so ejection rate falls
- Atrial pressure gradually rises from venous return
What happens in the isovolumetric relaxation stage of the cardiac cycle?
- Intraventricular pressure falls below aortic pressure so the aortic valve closes
- Closure of the aortic valve causes the second heart sound (S2)
- Decline in ventricular pressure
- Changes are isovolumetric as all valves are closed
- End systolic volume is reached
What happens in the reduced filling stage of the cardiac cycle?
- Filling rate slows as the ventricle reaches its inherent relaxed volume
What causes the first heart sound?
Closure of the AV valves (mitral & tricuspid)
What causes the second heart sound?
Closure of the semilunar valves (aortic & pulmonary)
When can a third heart sound be heard?
During early diastole
When can a fourth heart sound be heard?
During atrial contraction
What causes heart murmurs?
Disturbed flow if at rest but can be caused by turbulent flow during exercise in normal individuals