Cardiovascular Physiology

Question 1

What is the pathophysiology of atherosclerosis?

Answer 1

1. Endothelial dysfunction - alcohol / smoking
2. Proliferation leading to pro-inflammatory, pro-oxidant, proliferative and reduced nitric oxide bioavailability
3. Fatty infiltration of the subendothelial space by low-density lipoprotein (LDL) particles
4. Monocyte migration –> differentiate into macrophages –> digest LDL –> foam cells
5. Foam cell death –> increased inflammation
6. Smooth muscle proliferation and migration from the tunica media into the intima results in formation of a fibrous capsule covering the fatty plaque.

Question 2

How is ANP secreted?

Answer 2

Myocytes of right atrium and ventricle in response to increased blood volume

Question 3

What is the action of ANP?

Answer 3

Natriuretic, i.e. promotes excretion of sodium
Lowers BP
Antagonises actions of angiotensin II, aldosterone

Question 4

What are the stages of the cardiac action potential?

Answer 4

0 Rapid depolarisation Rapid sodium influx
1 Early repolarisation Efflux of potassium
2 Plateau Slow influx of calcium
3 Final repolarisation Efflux of potassium
4 Restoration of ionic concentrations

Resting potential is restored by Na+/K+ ATPase

Question 5

At resting ionic concentration what is happening to cardiac muscle cells?

Answer 5

There is slow entry of Na+ into the cell decreasing the potential difference until the threshold potential is reached, triggering a new action potential

Question 5

At resting ionic concentration what is happening to cardiac muscle cells?

Answer 5

There is slow entry of Na+ into the cell decreasing the potential difference until the threshold potential is reached, triggering a new action potential

Question 6

At what speed is the action potential conducted over the atria?

Answer 6

1 m/second

Question 7

At what speed is the action potential conducted through the AV node?

Answer 7

0.05 m/second

Question 8

What is the fastest conducting part of the heart?

Answer 8

Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart.

This allows a rapid and coordinated contraction of the ventricles

Question 9

How do you calculate the left ventricle ejection volume?

Answer 9

Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) * 100%

Question 10

How do you calculate the stroke volume?

Answer 10

Stroke volume = end diastolic LV volume - end systolic LV volume

Question 11

How do you calculate the cardiac output?

Answer 11

Cardiac output = stroke volume x heart rate

Question 12

How do you calculate pulse pressure?

Answer 12

Pulse pressure = Systolic Pressure - Diastolic Pressure

Question 13

What factors increase pulse pressure?

Answer 13

1. a less compliant aorta (this tends to occur with advancing age)
2. increased stroke volume

Question 14

What is the calculation for mean arterial pressure and why is it this case?

Answer 14

MAP = (2xDBP) + SBP / 3

Diastolic multiplied by 2 because it is twice the systolic in length

Question 15

What secretes endothelin?

Answer 15

secreted initially as a prohormone by the vascular endothelium and later converted to ET-1 by the action of endothelin converting enzyme