Cardio Flashcards
In anaemia how is the arterial PaO2 and PaCO2 affected?
chronic - no change
acute haemorrhage - hyperventilation may lower PaCO2
what is the formula for oxygen content?
What units should be used
(Hb concentration x 1.34 x SaO2 ) + (PaO2 x 0.023).
PaO2 in Kpa
use Hb in g/100ml e.g. 5g/dL
answer will be in ml/dL
in anaemia how would the mixed venous PO2 change?
lower
what type of receptors are arterial baroreceptors?
stretch receptors/ mechanoreceptors
how do baroreceptors respond to increased pressure
more stretch - more firing of AP - increased frequency
do aortic baroreceptors respond to PaO2?
no they are baroreceptors not chemoreceptors.
what is chronotrophy and ionotrophy?
iono - force of contraction
chrono = rate
what is stroke index?
SV divided by body surface area
what is dP / dt?
the rate at which pressure in heart rises - increased by ionotropy
what happens to SVR in rise in ICP?
increased to try compensate
increased via sympathetic output
cushings - bradycardia, high BP, irregular breathin
what does arterial hypoxaemia do to SVR?
increases it
Hypoxaemia causes sympathetic ns to activate.
Some circulations vasoconstrict and other vasodilate in response to hypoxia to divert blood to viral organs , overall effect is increased SVR
All via chemoreceptors
how does pulmonary vasculature compare to systemic
BP - pulmonary mean 15mmHg, systemic -100mmHG
lower resistance in pulmonary
around 16% of blood volume in pulmonary circulation at rest
how does temp affect cerebral blood flow?
rise in temp increased BF
what is the rate limiting step in NA synthesis
the conversion of tyrosine to DOPA is the rate limiting step in the synthetic pathway of norepinephrine
Tyrosine hydroxylase
how is SVR changed in pregnancy?
reduced due to progesterone
what substrates can the heart use?
glucose
fatty acids
ketones
what are the different physiological shunts?
**Thebesian veins ** - are numerous minute veins which return blood directly from cardiac muscle to the chambers of the heart. Blood draining directly into the left atrium and ventricle therefore contribute to physiological shunt.
**Bronchial veins **- drain into pulmonary vein
(Pulmonary interstitial venous drainage contribute to physiological shunt as a proportion returns to the heart via the pulmonary veins)
when does the aortic valve open?
slight delay after ventricular systole has started.
when does LV and aortic pressures peak?
just before end of systole
at end of systole the myocardium begins to relax and pressure in ventricle falls and aortic valve closes. pressure in aorta also falls slightly
Describe the SAN action potential…
phase 4 - slow depolarisation - Na
phase 0 - rapid upstroke - AP - Ca
phase 3 - repolarisation - K+
resting potential around -60mV
how does a wave of JVP correspond to cardiac cycle? and the ecg ?
a wave corresponds to atrial contraction hence occurs just before ventricular systole.
the p wave on ecg occurs with or slightly before atrial contraction
what does tricuspid regurgitation do to the JVP wave form?
prominent c and v waves
c = when ventricle contraction the tricuspid valve closes against atria to increase pressure, if there is regurg, the blood will actually flow in to increase pressure
v wave - atrial filling - hence in regurg already blood here so will be higher
is blood flow to the skin autoregulated? what does it depend on?
no autoregulation i.e. not regulated to meet metabolic needs of the skin
instead used for thermoregulation - sensitive to environmental temp, can bypass capillaries to conserve heat. undercontrol by sympathetic NS.
