Cardiovascular physiology intro Flashcards
What are the steps of the cardiac cycle?
Atrial systole Isovolumetric ventricular systole Rapid ventricular ejection Reduced ventricular contraction Isovolumetric ventricular relaxation Rapid ventricular filling Reduced ventricular filling
What is cardiac excitation-contraction coupling?
Voltage induced Ca2+ release into cells via L-type channels
Calcium induced calcium release (ryanodine receptors)
Ca2+ acts on troponin causing muscle contraction
Ca2+ reduced in relaxation by SERCA (sarcoplasmic ER Ca2+ ATPase) and by Ca2+/Na+ exchange
What factors effect cardiac stroke volume?
Afterload (the pressure against which the heart has to pump) -> increasing afterload decreases stroke volume
Preload (the pressure which works with the heart) -> decreasing preload decreases stroke volume (lower CVP, central venous pressure)
Autonomic nervous system:
SNS stimulation increases stroke volume
PSNS stimulation decreases stroke volume
What is the name of the graphs that show the relationship between EDP (end diastolic pressure) and stroke volume?
Frank-Starling curves
How to calculate pulse pressure
systolic - diastolic
How to calculate mean arterial pressure
MAP = diastolic + (systolic - diastolic)/3
Why is the calculation for mean arterial pressure not just simple average?
Because most of the cardiac cycle is in diastole
How is blood flow maintained in the aorta even in diastole?
There is recoil in the walls of the vessel, which during systole expand. Then the energy stored causes it to compress and continue the flow of blood even in diastole
How is the vascular system regulated by the sympathetic nervous system?
Sympathetic stimulation of the vascular system causes constriction of peripheral vessels meaning that the total peripheral resistance increases.
This is done via stimulation of alpha1 adrenergic receptors
How is the vascular system regulated by the parasympathetic nervous system?
Causes dilation of peripheral vessels.
No effect on TPR
This is done via action on muscarinic and NANC receptors (e.g. with NO)
What receptors does noradrenaline act on and what effect does this have on the cardiovascular system?
alpha1 and alpha2 receptors.
Causing cardioacceleration and vasoconstriction respectively.
What receptors does adrenaline act on and what effect does this have on the cardiovascular system?
alpha1 and alpha2 receptors and beta1 receptors
Causing cardioacceleration; vasoconstriction in vascular beds; and vasodilation in skeletal muscle respectively.
What causes the shape of the SAN ECG
Funny current is the beginning then large jump due to Ca entry, then K loss causes the repolarisation
What causes the shape of pacemakers’ ECG in the heart (not SAN) such as in the ventricles
Immediate large jump due to Na entry, slow decline due to a balance of K+ loss but Ca entry, then when Ca entry stops, the K+ loss is all thats left so there is a rapid depolarisation
What type of receptor does the sympathetic NS use to regulate CO
Beta-1
