Anaesthetics - Physiology Flashcards
what are dead spaces in the lungs?
areas where ineffective gas exchange occurs
what happens in a shunt in the lungs?
ventilation fails to supply the perfused parts of the lungs
difference between hypoxia and hypoxaemia?
hypoxia - tissues
hypoxaemia - blood
what does CO = ??
HR x SV
what is stroke volume?
volume of blood pumped out by the LV in each systolic contraction
what is EDV?
volume of blood in ventricles before contraction
what is preload?
volume that is stretching walls of the ventricles
what = preload?
stroke volume (volume ejected from the heart per heartbeat)
what does the frank starling mechanism say?
a higher EDV will lead to greater contraction of the ventricles and therefore an increase stroke volume
what is afterload?
resistance the heart is pumping into
what does stroke volume =?
SV = EDV - ESV
what does MAP =?
MAP = CO x TPR
how does muscle contraction occur?
Ca binds to troponin
this moves the tropmyosin complex off the actin binding site
myosin head binds to the actin filament
what is S1 closure of? what does it indicate?
mitral (L)
tricuspid (R)
systole
what is S2? what does it indicate?
aortic
pulmonary
start of diastole
how does heart filling occur?
passively into ventricles
atria contract, filling ventricles, S1 (AV valves close)
pressure rises in ventricles
semilunar valves open, blood flows to aorta/pulmonary artery
ventricles contract
S2 (semilunar close)
where are the baroreceptors found? what do these do?
aortic arch
carotid sinus
modify BP by vasoconstrict/dilate
what does parasympathetic control do to the heart? how?
slows HR
ACh on M2
what does sympathetic control do to the heart? how?
increases HR
decreases AV node delay
NA acting on B1 receptors
alpha cause vasoconstriction
what causes vasodilation and vasoconstriction?
adrenaline on B1 (dilate)
adrenaline on alpha (constrict)
what is FVC?
maximum volume that can be moved out during a breath
what is RV?
maximum volume left in lungs after max expiration
what is TV?
volume entering and leaving the lungs during a breath
what is FEV1?
volume of air expelled in one second
what is the haldane effect?
Hb decreases its affinity for CO2 if oyxgen is high in the lungs
facilitates removal of CO2
what are the parasympathetic controls in the lungs?
ACh
M3
contraction
increase mucus
what are the sympathetic controls in the lungs?
adrenaline
B2
dilation
decrease mucus
what generates breathing control?
medulla
how long should COCP be stopped before surgery?
2 weeks
