L54: CVS 3

Question 1

What is functional/ active hyperaemia?

Answer 1

The increase in blood flow associated with an increase in metabolic activity of an organ or tissue, e.g. exercise

Question 2

Provide an example of a condition as a result of inadequate blood flow.

Answer 2

• Critical limb ischemia;
• Reynaud’s;
• Coronary heart disease (myocardial infarction).

Question 3

What factors influence blood flow?

Answer 3

• Length of ‘tube’, i.e. vessel;
• Viscosity of fluid, i.e. blood;
• Pressure gradient;
• Radius.

Question 4

What equation is used to explain factors and blood flow rate?

Answer 4

Poiseuille Equation

Question 5

What’re the assumptions of Poiseuille Equation?

Answer 5

• Flow is laminar;
• Flow is non-pulsatile;
• Flow is through a uniform, straight pipe.

Question 6

Why is the viscosity of blood important?

Answer 6

For hydration and to prevent pooling/ stasis of blood (DVT)

Question 7

What is resistance, of blood flow, proportional to?

Answer 7

Diameter

smaller the diameter, the greater the resistance

Question 8

How does an increase in branching of blood vessels (arteries-arterioles-capillaries), effect resistance and therefore, flow?

Answer 8

• Increase in resistance due to narrowing of vessels;

- Decrease in flow.

Question 9

Explain why pressure decreases around systemic circulation?

Answer 9

• Velocity is highest at aorta and vena cava where there is less resistance and greatest pressure;
• Velocity decreases as surface area (branching) increases into small vessels and pressure drops.

Question 10

Which blood vessels have low pressure?

Answer 10

Veins

Question 11

Describe the structure of veins

Answer 11

• Large;
• Low pressure;
• Valves to direct blood to heart;
• Skeletal muscle pump;
• SNS release NA to constrict veins and increase return to heart.

Question 12

What are the skeletal-muscle pumps?

Answer 12

• In skeletal muscles;
• When contracted, valves open to increase blood return to the heart (preload);
• When relaxed, valves closed;
• Important for distribution and supply of blood in different circumstances.

Question 13

Where does venous blood returns to?

Answer 13

Right atria, ventricle

Question 14

What is preload?

Answer 14

The amount go blood in the right ventricle (i.e. deoxygenated, venous blood)

Question 15

What happens in preload increases?

Answer 15

Heart increase C.O. to pump blood out

problematic with angina

Question 16

What is used to reduce preload/ relieve angina?

Answer 16

Glyceryl trinitrate (GTN spray)

Question 17

How does GTN spray work?

Answer 17

• Increases venodilation;
• Reduced venous pressure;
• Reduced preload;
• Reduced C.O.;
• Reduced angina.

Question 18

What are the local controls for arterioles?

Answer 18

• Changes in O2/ CO2/ cellular metabolites;
• Blocking blood flow;
• Flow-auto-regulation.

Question 19

How do changes in O2/ CO2/ cellular metabolites effect local arterioles?

Answer 19

Vasodilation (increased blood supply)

i.e. active hyperaemia (active due to increased activity)

Question 20

How does blocking blood flow effect local arterioles?

Answer 20

Increase in blood flow, to replenish ischemia

i.e. reactive hyperaemia (reactive due to reacting to conditions)