Control of cardiac output

Question 1

Heart failure compensatory mechanism

Answer 1

1. BP falls->salt excretion reduces->BV increases->CVP increases->EDP increases
2. BP falls->sympathetic system activated->renin-angiotensin-aldosterone system activated–>promotes fluid retenttion->increases contractility and heart reate
3. greater venous blood volume and vvenoconstrifction increases CVP

Question 2

Effect of afterload on cardiac output

Answer 2

Initially: SV decreases because aortic pressure higher than ventricular pressure
However:
1. ejection fraction falls, more blood remains in heart which increasesd the end systolic pressire and volume restoring SV
2. ANREP response i.e. cardiac stretch due to fluid retention causes increase in Ca2+ secretion
3. Depression of CO by baroreceptor reflex

Question 3

CVP determined by?

Answer 3

Capacitance and amount of blood

Question 4

Effect of sympathetic and parasympathetic on pacemaker potential

Answer 4

Sympathetic (increases funny current, faster rate of diastolic depolarization, faster hear rate)
Parasympathetic (decreases funny current, opens KACh channels, slower rate of diastolic depolarisation, slower heart rate)

Question 5

what factors affect cardiac output?

Answer 5

CO=HR (affected by ANS aka parasympathetic=HR and sympathetic stimulation=HR, contractility, SV) xSV (affected by EDV and ESV)