Cardio

Question 1

In anaemia how is the arterial PaO2 and PaCO2 affected?

Answer 1

chronic - no change
acute haemorrhage - hyperventilation may lower PaCO2

Question 2

what is the formula for oxygen content?
What units should be used

Answer 2

(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

Question 3

in anaemia how would the mixed venous PO2 change?

Answer 3

lower

Question 4

what type of receptors are arterial baroreceptors?

Answer 4

stretch receptors/ mechanoreceptors

Question 5

how do baroreceptors respond to increased pressure

Answer 5

more stretch - more firing of AP - increased frequency

Question 6

do aortic baroreceptors respond to PaO2?

Answer 6

no they are baroreceptors not chemoreceptors.

Question 7

what is chronotrophy and ionotrophy?

Answer 7

iono - force of contraction
chrono = rate

Question 8

what is stroke index?

Answer 8

SV divided by body surface area

Question 9

what is dP / dt?

Answer 9

the rate at which pressure in heart rises - increased by ionotropy

Question 10

what happens to SVR in rise in ICP?

Answer 10

increased to try compensate
increased via sympathetic output
cushings - bradycardia, high BP, irregular breathin

Question 11

what does arterial hypoxaemia do to SVR?

Answer 11

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

Question 12

how does pulmonary vasculature compare to systemic

Answer 12

BP - pulmonary mean 15mmHg, systemic -100mmHG

lower resistance in pulmonary

around 16% of blood volume in pulmonary circulation at rest

Question 13

how does temp affect cerebral blood flow?

Answer 13

rise in temp increased BF

Question 14

what is the rate limiting step in NA synthesis

Answer 14

the conversion of tyrosine to DOPA is the rate limiting step in the synthetic pathway of norepinephrine

Tyrosine hydroxylase

Question 15

how is SVR changed in pregnancy?

Answer 15

reduced due to progesterone

Question 16

what substrates can the heart use?

Answer 16

glucose
fatty acids
ketones

Question 17

what are the different physiological shunts?

Answer 17

**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)

Question 18

when does the aortic valve open?

Answer 18

slight delay after ventricular systole has started.

Question 19

when does LV and aortic pressures peak?

Answer 19

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

Question 20

Describe the SAN action potential…

Answer 20

phase 4 - slow depolarisation - Na
phase 0 - rapid upstroke - AP - Ca
phase 3 - repolarisation - K+

resting potential around -60mV

Question 21

how does a wave of JVP correspond to cardiac cycle? and the ecg ?

Answer 21

a wave corresponds to atrial contraction hence occurs just before ventricular systole.
the p wave on ecg occurs with or slightly before atrial contraction

Question 22

what does tricuspid regurgitation do to the JVP wave form?

Answer 22

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

Question 23

is blood flow to the skin autoregulated? what does it depend on?

Answer 23

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.