Cardiovascular Physiology

Question 1

Description and function of elastic arteries?

Answer 1

Aorta
Wide lumen, elastic wall
Damp pressure variations

Question 2

Description and function of muscular arteries?

Answer 2

Wide lumen, strong non-elastic wall

Low resistance conduit

Question 3

Description and function of resistance vessels?

Answer 3

Narrow lumen, thick contractile wall

Allow regional redirection of blood

Question 4

Description and function of capillaries?

Answer 4

Narrow lumen, single cell wall, for diffusion

Question 5

Description and function of veins

Answer 5

Wide lumen, distensible wall

Low resistance conduit and resevoir, allows fractional distribution of blood

Question 6

What releases nor/adrenaline?

Answer 6

Sympathetic nerves (noradrenaline)
Adrenal medulla (adrenaline)

Question 7

What does noradrenaline act on?

Answer 7

B1-receptors on sino-atrial node

Question 8

What is the parasympathetic effect on the nervous system?

Answer 8

Vagus release of ACh

Question 9

What is the effect of ACh?

Answer 9

Hyperpolarisation AND decreased slope of pacemaker potential

Question 10

What does ACh act on?

Answer 10

Muscarinic receptors on sinoatrial node

Question 11

What is Starling’s Law?

Answer 11

Energy of contraction of proportional to the initial length of the cardiac muscle fibre

Question 12

How does increased venous return increase stroke volume?

Answer 12

Increased stretch due to increased end diastolic volume

Question 13

What is afterload?

Answer 13

The load against which the muscle tries to contract

Question 14

What general factors effect afterload

Answer 14

Cardiac output

Total peripheral resistance

Question 15

If TPR increases, what will the effect be on stroke volume? Why?

Answer 15

Decrease

More energy wasted on building up sufficient pressure

Question 16

What is the effect of the sympathetic nervous system on stroke volume?

Answer 16

Increased, shorter contractility

Question 17

What is the effect of the parasympathetic system on stroke volume?

Answer 17

None

Question 18

What effect does hypercalcaemia have on stroke volume?

Answer 18

Increased stroke volume

Reduced EDV

Question 19

Effect of hypocalcaemia, ischaemia and barbiturate on stroke volume?

Answer 19

Reduced stroke volume

Increased end diastolic volume

Question 20

CO =

Answer 20

HR x SV

Question 21

How does artificially increasing HR to increase CO cause a drop in SV?

Answer 21

Shortened cardiac interval cuts into filling phase
Reduced EDV
Reduced Stroke volume

Question 22

Gross structure of capillaries

Answer 22

Thin wall
Small diameter (SA:V)

Question 23

What is the structure of continuous capillaries? Where are they found?

Answer 23

No clefts or channels

Found in brain

Question 24

What is the structure of fenestrated capillaries? Where are they found?

Answer 24

Clefts and channels

Found in intestine

Question 25

What is the structure of discontinuous capillaries? Where are they found?

Answer 25

Clefts and massive channels

Question 26

Anti-clotting mechanisms of the endothelium

Answer 26

``` Stop blood contacting collagen Prostacyclin and NO Tissue factor pathway inhibitor Thrombomodulin and heparin t-PA ```

Question 27

Diffusion from capillary to cell is:

Answer 27

Self-regulating Non-saturable Non-polar

Question 28

How do polar substances cross from capillary to cell?

Answer 28

Clefts and channels

Question 29

How much fluid is filtered every day? How much is lost? Where does it go?

Answer 29

20L, 3L lost | Drained through lymphatics

Question 30

What macrofactors cause Oedema

Answer 30

Lymphatic Obstruction Raised CVP Hypoproteinemia Increased capillary permeability

Question 31

What four pressures dictate fluid exchange in capillaries?

Answer 31

Capillary Hydrostatic ISF Hydrostatic Plasma osmotic ISF Osmotic

Question 32

Function of Heparin and Thrombomodulin

Answer 32

Inactivate thrombin

Question 33

What is the function of Tissue Factor Pathway Inhibitor?

Answer 33

Stops thrombin production

Question 34

Function of prostacyclin and NO

Answer 34

Inhibit platelet aggregation

Question 35

What is the function of t-PA?

Answer 35

Plasminogen activator Plasminogen > plasmin Plasmin digests clot

Question 36

What are the 5 stages of the cardiac cycle?

Answer 36

1. Late Diastole 2. Atrial systole 3. Isovolumic ventricular contraction 4. Ventricular ejection 5. Isovolumic ventricular relaxation

Question 37

What is Isovolumic ventricular contraction?

Answer 37

First phase of ventricular contraction | Pushes AV valves shut but doesn't open semilunar valves

Question 38

When does Ventricular ejection occur?

Answer 38

When the pressure in the ventricle exceeds the pressure in the arteries

Question 39

What is Isovolumic ventricular relaxation?

Answer 39

Ventricles relax and pressure falls, causing blood to flow back into the cusps and snap the aortic valve shut

Question 40

When is the volume of the left ventricle greatest?

Answer 40

End of diastole (EDV)

Question 41

When is the volume of the left ventricle smallest?

Answer 41

End of systole (ESV)