L10-Characteristics of circulation through different organs

Question 1

What are the two main tasks of the coronary circulation?

Answer 1

Maintain secure O2 supply to the coronary muscle

Alter local flow according to activity (metabolic regulation)

Question 2

Why must the flow to the coronary arteries be increased in order to meet increased oxygen demand?

Answer 2

As at rest there is a very large arterial-venous O2 difference. This means that the maximal amount of O2 is extracted at rest without increasing the flow.

Question 3

What is the circumflex artery a branch from?

Answer 3

The Left coronary artery

Question 4

Why is flow to the coronary muscle intermittent?

Answer 4

When the pressure in the ventricle is greater than the pressure in the aorta then the vessels are compressed and blood will not flow.

Question 5

What happens during the start of systole?

Answer 5

Blood flow in the coronary arteries can actually reverse due to contraction of the ventricle compressing the vessels

Question 6

What is the pressure range for the coronary arteries myogenic autoregulation?

Answer 6

60-180mmHg

Question 7

What is the dominant form of pressure control in the coronary arteries?

Answer 7

Metabolic hyperaemia- Directs blood flow to other organs by vasodilation when not needed at heart or if too greater pressure

Question 8

What is angina the result of?

Answer 8

arthritic plaque building up in the arteries of the heart and restricting blood flow

Question 9

What are the two main functions of cerebral circulation?

Answer 9

Maintain totally secure O2 supply to the brain tissue

Alter local flow according to active functional hyperaemia.

Question 10

What is the structural advantage advantage of the circle of willis?

Answer 10

Short arteries in a dense capillary network that ensures that the brain is still perfused if the carotid arteries are blocked

Question 11

What is the blood-brain barrier formed of?

Answer 11

endothelial cells sealed with tight junctions to prevent bulk flow. Also no vesicular transport, this maintains the internal environment.

Question 12

What percentage of the cardiac output goes to the cerebral circulation?

Answer 12

15%

Question 13

What does an increase in CO2 in the cerebral vessels result in?

Answer 13

The cerebral vessels are very responsive to CO2 and hence causes vasodilation to cause an increase in flow.

Question 14

What is the cerebral response to low CO2 and what does this cause?

Answer 14

It causes vasoconstriction that is responsible for the dizziness felt when hyperventilating

Question 15

How much can sympathetic innervation increase cerebral resistance by?

Answer 15

only 20-30%

Shifts autoregulatory curve right

Question 16

How do you calculate the cerebral perfusion pressure?

Answer 16

The average blood pressure - intracranial pressure

Question 17

What is the effect of being warm on cutaneous circulation?

Answer 17

Decreased sympathetic activity to alpha 1 adrenoreceptors which results in vasodilation of peripheral vessels.