review of cardiac physiology Flashcards
describe the cardiac cycle
systole and diastole
diastole = blood flows passively from atria to ventricles
systole = pulmonic and aortic valves open = permit blood from ventricles into pulmonary and systemic circulation
what do you need for cardiac output
LV overcome pressure to open aortic valve
equation for cardiac output
CO = stroke volume x HR
important for heart failure
equation for arterial pressure
arterial pressure = cardiac output x preipheral resistance
important for hypertension
equation for 02 utilisation
o2 utilisation = o2 delivery x (XAO2 - CvO2)
important for ischaemic heart disease
what is a normal cardiac output
5L/min
what is a normal stroke V
5000/60
70-80mL
SV is influenced by what
preload and afterload
what are preload and afterload
preload = end-diastolic pressure when ventricle is filled (at end-diastolic volume)
afterload: the pressure in aorta (resistane in circulation)
how is increase in cardiac output acheived
intrinsic reg of ouput
changes in HR via autonomic ns control
how is intrinsic cardiac reg of output achieved
frank starling mechanism
= greater return of venous blood = greater output
bainbridge reflex = inc HR with inc atrial stretch
what happens when cardiac output decreases
o2 delivery to tissues is compromised
inability to increase CO during exercise
caused by ischaemia, coronary disease, valvular disease
how can arterial pressure be comprehended
ohms law = change in pressure = flow x resistance
what influences blood pressure
altered CO
changes in vascular resistance
peripheral resistance due to symp vasoconstrictor nerves
how is arterial pressure controlled acutely
through the baroreflex
