Cardiology: Special Circulations

Question 1

Where do the coronary arteries arise from?

Answer 1

Base of the aorta

Question 2

Where does the coronary sinus drain to?

Answer 2

Right atrium

Question 3

What are the special adaptations of the coronary circulation?

Answer 3

High capillary density
High basal blood flow
High oxygen extraction

Question 4

What is the consequence of the coronary ciculation having a high oxygen extraction?

Answer 4

Extra oxygen (when required) cannot be supplied by increasing extraction- it must be supplied by increased blood flow.

Question 5

What are the intrinsic mechanisms that control coronary flow?

Answer 5

Decreased PO2 results in vasodilation
Metabolic hyperaemia matches flow demand
Adensoine release from ATP when the heart muscle is working hard is a potent vasodilator

Question 6

What are the extrinsic mechanisms which control coronary flow?

Answer 6

Sympathetic stimulation- results in increased HR and SV- increased ATP break down and casodilation
Adrenaline activates B2 adrenoceptors causing vasodilation

Question 7

When is coronary blood flow at its peak in the cardiac cycle?

Answer 7

Diastole

Question 8

What supplies the brain?

Answer 8

Internal carotids

Vertebral Arteries

Question 9

What forms the circle of willis?

Answer 9

BASILAR (two vertebral arteries) and the carotid arteries anastomoses

Question 10

What is the purpose of the circle of willis?

Answer 10

Ensures that brain is perfused if major artery becomes blocked

Question 11

What happens if there is an obstruction in a smaller branch?

Answer 11

That area of the brain is deprived of blood

Question 12

Name the two types of stroke?

Answer 12

Haemorrhagic

Ischaemic

Question 13

In what MAP range can the autoregulation of the brain control blood flow?

Answer 13

60-160mmHG

Question 14

What happens to cerebral flow is MAP rises?

Answer 14

Vasoconstriction- limits blood flow

Question 15

What happens is MAP decreases?

Answer 15

Vasodilation - decreased blood flow

Question 16

What MAP can result in brain damage

Answer 16

50 mmHg or less

Question 17

What effect does and increased of CO2 have on the cerebral circulation?

Answer 17

Vasodilation

Question 18

What effect does a decrease of Co2 have on the cerebral circulation?

Answer 18

Vasoconstriction

Question 19

What is normal intracranial pressure?

Answer 19

8-13mmHg

Question 20

How do you calculate cerebral perfusion pressure?

Answer 20

MAP-ICP

Question 21

What happens if you increase ICP?

Answer 21

Decreased CPP- decreased cerebral flow

Question 22

What can be a consequence of raised ICP?

Answer 22

Failure of autoregulation

Question 23

What is the BBB permeable to?

Answer 23

Oxygen
CO2
Glucose

Question 24

What is the BBB impermeable to?

Answer 24

Hypdrophillic substances eg ions, catecholamines and proteins

Question 25

What is the pulmonary BP compared to the systemic BP?

Answer 25

Much lower pressure

Question 26

What is the advantage of the pulmonary circulation being so low?

Answer 26

Protects against oedema because absorptive forces exceed filtration forces

Question 27

What does hypoxia cause in the pulmonary circulation?

Answer 27

VASOCONSTRICTION- this is the opposite to the systemic circulation

Question 28

Why does hypoxia cause vasconstriction in the pulmonary circulation it do this?

Answer 28

Diverts blood away from poorly ventilated areas

Question 29

Why is resting blood flow in the systemic circulation low?

Answer 29

Sympathetic vasocontrictor tone

Question 30

What happens to the muscles in exercise?

Answer 30

Metabolic hyperaemia overcomes sympathetic vasoconstrictor activity Adrenaline causes vasodilation

Question 31

What is the skeletal muscle pump?

Answer 31

COntraction of muscles in lower limbs aids venous return to the heart

Question 32

What condition arises due to incompetent venous valves?

Answer 32

Varicose veins

Question 33

Why does this condition not lead to a chronic decrease in CO?

Answer 33

Compensatory mechanism chronically increased BLOOD VOLUME