3. The Heart as a Pump Flashcards
Which circulation has higher pressure, systemic or pulmonary?
Systemic.
Give the typical pressure for the following chambers and vessels. Left atrium Left ventricle Aorta Right atrium Right ventricle Pulmonary artery.
LA 8-10 mmHg
LV 120mmHg in systole, 10mmHg in diastole.
Aorta 120mmHg systole, 80mmHg in diastole.
RA 0-4mmHg.
RV 25mmHg in systole, 4mmHg in diastole.
PA 25mmHg in systole, 10mmHg in diastole.
What is the key driver in cardiac muscle contraction?
Calcium levels rising, from action potential.
What are the four valves of the heart?
Tricuspid valve, mitral valve, pulmonary valve and aortic valve.
What holds the mitral and tricuspid valves in place?
Chordae tendinaea (attach cusps of valves to papillary muscles).
What is the normal conduction of the heart?
Pacemaker calls in the sinoatrial node generate an action potential. Spreads over the atria in atrial systole. Action potential held at the atrioventricular node for 120ms. Excitation spreads down septum between ventricles. Then spreads through ventricular myocardium from inner to outer surface. The ventricles contract from the apex upwards.
What are the 7 phases of the cardiac cycle?
Atrial contraction. Isovolumetric contraction. Rapid ejection. Reduced ejection. Isovolumetric relaxation. Rapid filling. Reduced filling.
What does Wiggers diagram show?
The pressure changes over the cardiac cycle of the aorta, left atria, left ventricle, and the ventricular volume change.
What happens to the pressure in the heart in atrial contraction?
Atrial pressure rises due to atrial systole, A wave. Ventricular volume increases a little bit as atrial contraction causes the last 10% of ventricular filling. P wave on the ECG shows the onset of atrial depolarisation.
When is ventricular volume at its greatest?
At the end of atrial contraction, end-diastolic volume.
What happens to the pressures in the heart during isovolumetric contraction?
Ventricular pressure rises rapidly, this causes closing of the mitral valve - C wave on atrial pressure curve.
What happens to the pressures in the heart in rapid ejection?
Atrial pressure decreases initially - X descent, there is a rapid decrease in ventricular volume as blood is ejected into the aorta. Intraventricular pressure exceeds the aortic pressure so the aortic valve opens.
What happens to the pressures in the heart in reduced ejection?
Atrial pressure gradually rises because of the venous return from the lungs - V wave. Ventricular pressure starts to fall as it depolarises.
What happens to the pressures in the heart during isovolumetric relaxation?
Intraventricular pressure falls below the aortic pressure so the aortic valve closes. There is a diacritic notch in aortic pressure caused by the valve closing. The ventricles are still at their lowest volume.
How can stroke be calculated form ventricular volumes?
End diastolic volume - end systolic volume = stroke volume.
