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FRCA Course Papers > 13. CVS Physiology > Flashcards

13. CVS Physiology Flashcards

1
Q

What is the resting coronary blood flow?

A

250 mL/min

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2
Q

How much is coronary blood extraction?

A

Coronary O2 extraction is about 110 mL/L/min (55% of the available content)

Therefore supplies muscle that extracts 40 mL/L of oxygen per minute at rest

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3
Q

Do coronary arteries undergo autoregulation?

A

It autoregulates between a MAP range of 50-120 mmHg

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4
Q

What is the normal cardiac ejection fraction?

A

70%

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5
Q

What is the dicrotic notch represent?

A

rebound of the aortic valve

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6
Q

Normal LV end systolic volume?

A

30 mL

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7
Q

Normal stroke volume?

A

70ml

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8
Q

normal LVEDP

A

100 mm Hg

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9
Q

What can be used to measure pulmonary vascular resistance?

A

A Swan-Ganz catheter can measure cardiac output and PA pressure, enabling the PVR to be calculated.

  • a flow-directed balloon catheter with a thermistor tip.
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10
Q

How does 5-HT affect pulmonary artery pressure?

A

5-HT produces pulmonary vasoconstriction, raising PAP

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11
Q

What is the mean pulmonary artery pressure?

What fraction is that of systemic circulation?

A

Mean PAP is 15 mmHg (around one sixth of systemic MAP), with both circulations having the same flow.

normally 25/10 mm Hg

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12
Q

The pressure drop is greater across major veins or major arteries?

A

They are similar in major vessels.

The largest drop is seen in arterioles.

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13
Q

The pressure drop across the hepatic portal bed is similar to that across the splenic vascular bed? T/F

A

False.

The hepatic portal bed is a very low pressure/low resistance one.

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14
Q

In the hepatic portal vein the pressure is approximately 3 times higher than that in the inferior vena cava.

T/F

A

False.

Normal hepatic portal vein pressure is 5-10 mmHg, little different from that in the IVC

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15
Q

How does the pressure drop between vary between pulmonary and systemic circulation differ?

A

The drop across the pulmonary circulation is only about a sixth of that in the systemic circulation.

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16
Q

in a CVP waveform, what does the ‘c’ wave represent?

A

The c wave occurs during early ventricular contraction (systole),

as the closed tricuspid valve bulges back into the right atrium.

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17
Q

What does the ‘a’ wave represent in a CVP waveform?

A

The a wave results from atrial contraction, so Is absent in AF

The a wave occurs in late diastole, long after aortic valve closure.

18
Q

What does the ‘v’ wave represent in the CVP waveform?

A

The v wave occurs during diastole.

The v wave occurs during ventricular relaxation (diastole) but before the tricuspid valve opens.

19
Q

Does the LV eject more blood per beat than the RV?

A

No, equal volumes.

20
Q

During strenuous work, does the LVEDV increase or decrease?

A

Decreases because more blood will be ejected with increased ejection fraction.

21
Q

At what RV pressure does the pulmonary valve open?

A

10-12 mmHg

22
Q

LV pressure during diastole?

A

5 mmHg

23
Q

What blood does the ductus venosus contain?

A

The ductus venosus contain blood returning from the placenta via the umbilical vein, oxygenated blood.

24
Q

TRUE OR FALSE:

In fetal circulation - blood entering the right atrium can reach the systemic circulation without passing through the left side of the heart.

A

True.

Blood from the RA can reach the systemic circulation via the RV, pulmonary artery and ductus arteriosus.

It is mostly SVC blood that follows this pathway, which is largely kept separate from IVC blood via streaming in the RA.

25
Q

In fetal circulation: why is the PaO2 in the descending aorta lower than in the aortic arch?

A

Blood in the descending aorta has a lower PO2 because deoxygenated blood has joined via the ductus arteriosus.

26
Q

Do peripheral chemoreceptors respond to changes in pH?

A

Yes, a metabolic acidosis is sensed by these peripheral chemoreceptors.

27
Q

What view is Lead II ECG?

A

Lead II looks at the view from right arm to left leg.

28
Q

Up to what volume of blood does the LV diastolic remain compliant?

A

The LV remains very compliant up to around 120 mL.

29
Q

Why does the heart have such a high A-VO2 difference?

A

Coronary oxygen extraction is high, at an extraction ratio of 0.55-0.6

30
Q

Which receptors in the are innervated by the vagus nerve in the heart?

A
  • M2 receptors are present in the heart
31
Q

What ions does vagus innervation in the heart effect?

A

The vagus works mainly by increasing permeability to potassium.

32
Q

What is the normal RV thickness?

A

RV = 3 - 4 mm thick

33
Q

What is pulmonary capillary hydrostatic pressure?

A

10 mmHg

12 mmHg, falling to around 7 at the distal end; this is the main reason for minimal fluid loss into the alveoli

34
Q

Glomerular capillary hydrostatic pressure?

A

55 mmHg, enabling a large volume of filtrate to be produced

35
Q

What is normal plasma oncotic pressure?

A

25 mmHg

36
Q

What are the right and left ventricular:

  1. end diastolic volumes
  2. end systolic volumes?
A

Similar volumes for LV and RV.

end-diastolic - 100 - 110 mL
end systolic - 30 - 40 mL

37
Q

RV pressure normal value?

How does RV pressure compare to the LV pressure?

A

25/0 mmHg

RV systolic pressure is about one fifth of the LV

38
Q

Which component of plasma generates the most osmotic pressure?

A

Electrolytes (mostly sodium and chloride) make up the vast majority of plasma osmotic pressure

  • it is the number of particles, not their size which counts.
39
Q

How much fluid daily returns via:

  1. lymphatic system
  2. venous end
A
  1. lymphatic end - 2L return.

2. venous end - 18 L return.

40
Q

How long does an action potential in a cardiac myocyte last?

A

300 ms

41
Q

The following produce a fall in the systemic vascular resistance:

Select true or false for each of the following statements.

A.	Hypercapnia			
B.	Pregnancy			
C.	Increased intracranial pressure		
D.	ANP				
E.	Changing from fetal to adult circulation
A

A. True. Hypercapnia produces vasodilatation

B. True. Vasodilatation occurs during pregnancy, largely mediated by progesterone

C. False. As the ICP rises, Cushing’s response leads to vasoconstriction to raise MAP.

D. True. ANP produces vasodilatation as well as natriuresis

E. False. Loss of the placental circulation at birth increases SVR

FRCA Course Papers (15 decks)

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