Cardiovascular physiology and action potentials Flashcards
Describe what happens during the 5 phases of the cardiac action potential
Phase
0 Rapid Na influx (depolarisation)
1 Efflux of potassium (Early repolarisation)
2 Slow influx of calcium (Plateau)
3 Efflux of potassium (Final repolarisation)
4 Resting potential is restored by Na+/K+ ATPase
How is a new cardiac action potential created?
slow entry of Na+ into the cell decreasing the potential difference until the threshold potential is reached, triggering a new action potential
Where in the heart is conduction velocity fastest?
Ventricular conduction Purkinje fibres (2-4 m/sec)
Where is conduction slowest in the heart?
AV node
Atrial conduction 1 m/sec
AV conduction 0.05 m/sec
Ventricular conduction Purkinje fibres (2-4 m/sec)
How is the Left ventricular ejection fraction calculated?
LVEF = (stroke volume / end diastolic LV volume ) * 100%
end diastolic LV volume - end systolic LV volume = ?
Stroke volume
stroke volume x heart rate =?
cardiac output
Systolic Pressure - Diastolic Pressure =?
pulse pressure
Factors which increase Pulse Pressure
a less compliant aorta (advancing age)
increased stroke volume
mean arterial pressure / cardiac output = ?
Systemic vascular resistance