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Physiology > Cardiology: Special Circulations > Flashcards

Cardiology: Special Circulations Flashcards

1
Q

Where do the coronary arteries arise from?

A

Base of the aorta

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2
Q

Where does the coronary sinus drain to?

A

Right atrium

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3
Q

What are the special adaptations of the coronary circulation?

A

High capillary density
High basal blood flow
High oxygen extraction

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4
Q

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

A

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

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5
Q

What are the intrinsic mechanisms that control coronary flow?

A

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

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6
Q

What are the extrinsic mechanisms which control coronary flow?

A

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

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7
Q

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

A

Diastole

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8
Q

What supplies the brain?

A

Internal carotids

Vertebral Arteries

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9
Q

What forms the circle of willis?

A

BASILAR (two vertebral arteries) and the carotid arteries anastomoses

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10
Q

What is the purpose of the circle of willis?

A

Ensures that brain is perfused if major artery becomes blocked

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11
Q

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

A

That area of the brain is deprived of blood

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12
Q

Name the two types of stroke?

A

Haemorrhagic

Ischaemic

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13
Q

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

A

60-160mmHG

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14
Q

What happens to cerebral flow is MAP rises?

A

Vasoconstriction- limits blood flow

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15
Q

What happens is MAP decreases?

A

Vasodilation - decreased blood flow

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16
Q

What MAP can result in brain damage

A

50 mmHg or less

17
Q

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

A

Vasodilation

18
Q

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

A

Vasoconstriction

19
Q

What is normal intracranial pressure?

A

8-13mmHg

20
Q

How do you calculate cerebral perfusion pressure?

A

MAP-ICP

21
Q

What happens if you increase ICP?

A

Decreased CPP- decreased cerebral flow

22
Q

What can be a consequence of raised ICP?

A

Failure of autoregulation

23
Q

What is the BBB permeable to?

A

Oxygen
CO2
Glucose

24
Q

What is the BBB impermeable to?

A

Hypdrophillic substances eg ions, catecholamines and proteins

25
Q

What is the pulmonary BP compared to the systemic BP?

A

Much lower pressure

26
Q

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

A

Protects against oedema because absorptive forces exceed filtration forces

27
Q

What does hypoxia cause in the pulmonary circulation?

A

VASOCONSTRICTION- this is the opposite to the systemic circulation

28
Q

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

A

Diverts blood away from poorly ventilated areas

29
Q

Why is resting blood flow in the systemic circulation low?

A

Sympathetic vasocontrictor tone

30
Q

What happens to the muscles in exercise?

A

Metabolic hyperaemia overcomes sympathetic vasoconstrictor activity
Adrenaline causes vasodilation

31
Q

What is the skeletal muscle pump?

A

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

32
Q

What condition arises due to incompetent venous valves?

A

Varicose veins

33
Q

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

A

Compensatory mechanism chronically increased BLOOD VOLUME

Physiology (17 decks)

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