2.1 Cardic cycle Flashcards
What is isovolumetric contraction.
Ventricular contraction when all valves are closed. This increases ventricular pressure but as the valves are closed the volume remains unchanged.
What produces the first heart sound?
Closing of the mitral valve.
What causes the mitral valve to close?
When the left ventricle pressure exceeds the left atrial pressure just before isovolumetric contraction
Describe systole.
Wave of depolarisation arrives
Ca2+ channels open.
P(Ventricle) > P(Atria)
Mitral valve closes
P(Ventricle) rises
Isovolumetric contraction
P(Ventricle) > P(Aortic)
Aortic valve opens
Ejection begins
What produces the second heart sound?
Closing of the aortic valve (semilunar valve).
Describe diastole.
P(Ventricle) decreases
Phase of reduced ejection
P(Ventricle) > P(aortic)
Aortic valve (SL) closes Isovolumetric ventricular relaxation
P(Ventricle) > P(Atria)
Mitral valve (AV) opens Ventricles fill with blood
Atria contract
P(Ventricle) > P(Atria)
Mitral valve closes
What is the duration of systole?
0.3s
What is the duration of diastole?
0.5s
What is end systolic volume?
The volume of blood remaining in the ventricle after systole.
What is end diastolic volume?
The volume of blood remaining in the ventricles after diastole.
Define preload…
The volume of blood in the ventricles before contraction.
Define afterload…
The pressure that the heart must work against to eject blood in systole during the ejection phase.
Define contractility
The strength of the heart to contract during systole
Define elasticity
Myocardial ability to recover its original shape after systolic stress.
Define compliance
How easily a hearts chamber expands when filled with blood
Define diastolic distensibility
The pressure required to fill the ventricle to the same diastolic volume.
Explain Starling’s law.
The larger the volume of the heart, the greater the sarcomeres are stretched and the more forceful the contraction.
With relation to Starling’s law, what is the effect of an increased venous return?
End-DV will increase and so SV increases and so Cardiac output also increases as CO=SVxHR.
Give the equation for stroke volume.
SV=End DV-End SV.
Give the equation for cardiac output.
CO=SVxHR.
Define cardiac output.
The volume of blood each ventricle pumps per unit time
Give the equation for mean arterial pressure.
MAP = DP + 1/3(SP-DP).
What is pulse pressure?
The difference between systolic and diastolic blood pressure. It represents the force the heart generates when it contracts.
Give the equation for pulse pressure.
PP=SP-DP.
What is a normal healthy pulse pressure?
40mmHg
Give the equation for blood pressure.
BP=COxTPR (total peripheral resistance)
What is Poiseuille’s equation?
Q=r^4.
Q= Blood flow
r= radius of blood vessel
What is Ohm’s law?
F=ΔP/R.
F= change in pressure/resistance.
Is there a point in the cardiac cycle when both atrial and ventricular diastole occur together?
Yes: when the ventricles are relaxing and the atria are filling (before atrial contraction).
Diastole: what is diastasis?
When LVp = LAp. Net movement of blood is zero. This is the time between ventricular suction and atrial contraction.
What equation explains why small changes in the diameter of a blood vessel have a great effect on the resistance to flow of a fluid through that vessel?
Poiseuille’s equation. Q=r^4.
Does blood flow to the heart occur during diastole or systole?
Diastole
