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Cardiovascular Week 4 2016/17 > 1: Special circulations > Flashcards

1: Special circulations Flashcards

1
Q

Where do the right and left coronary arteries arise from?

A

Base of the aorta

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2
Q

Where does coronary venous blood drain into?

A

Coronary sinus

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3
Q

The coronary circulation has a ___ capillary density.

A

high

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4
Q

What occurs in the capillaries?

A

Gas exchange (oxygen and carbon dioxide)

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5
Q

What is the oxygen extraction rate in the coronary circulation compared to the normal rate in the body?

A

75% compared to 25%

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6
Q

The only means of increasing coronary oxygen supply is increasing blood flow -why?

A

Oxygen extraction is already greater compared to normal circulation - cannot be increased any more

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7
Q

Reduced partial pressure of oxygen in the coronary arteries causes ___.

A

vasodilation

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8
Q

Which chemical, found in ATP, is a potent vasodilator?

A

Adenosine

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9
Q

The net effect of sympathetic stimulation in the coronary arteries is ___.

A

vasodilation.

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10
Q

The net effect of sympathetic stimulation in the coronary arteries is ___.

A

vasodilation.

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11
Q

Most left coronary blood flow occurs during diastole - why?

A

During systole, subendothelial coronary arteries are squeezed by ventricular contraction

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12
Q

Keeping in mind the point during the cardiac cycle at which left coronary blood flow is greatest, what could cause reduced coronary blood flow?

A

Reduced length of diastole (e.g tachycardia)

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13
Q

Why is there no difference in right coronary blood flow during systole compared to diastole?

A

Pressure in right ventricle isn’t high enough to squeeze coronary arteries

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14
Q

Which blood vessels supply the brain with oxygen?

A

Internal carotid arteries

Vertebral arteries

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15
Q

Grey matter is (sensitive/insensitive) to hypoxia.

A

sensitive

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16
Q

Arteries supplying the brain anastomose to form what?

A

Circle of Willis

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17
Q

What is the benefit of having a Circle of Willis?

A

Cerebral perfusion maintained even if one carotid artery is blocked

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18
Q

What causes stroke?

A

Blocked blood supply to a region of the brain

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19
Q

What are the two main types of stroke?

A

Haemorrhagic (bleeding) stroke, caused by blood leaking out of arterial wall

Ischaemic stroke - atheroma

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20
Q

Within which range of MAP can autoregulation of cerebral blood flow work?

A

60 - 160 mmHg

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21
Q

Sympathetic stimulation has a (significant / insignificant) effect on cerebral blood flow

A

insignificant

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22
Q

If MAP increases, cerebral blood vessels automatically __ to limit blood flow.

A

constrict

23
Q

If MAP decreases, cerebral blood vessels automatically __ to increase blood flow.

A

dilate

24
Q

What occurs in the brain if MAP < 50mmHg?

A

Confusion, fainting, brain damage

25
Q

Why can hyperventilation lead to fainting?

A

Decreased partial pressure of CO2 (blown off) causes vasoconstriction (cerebral blood flow decreases)

26
Q

Increased partial pressure of CO2 causes ___.

A

vasodilation

27
Q

What is intracranial pressure?

A

Pressure within the skull

28
Q

What is the normal range for intracranial pressure?

A

8 - 13 mmHg

29
Q

How can cerebral perfusion pressure be calculated?

A

CPP = MAP - ICP

30
Q

Why may intracranial blood pressure increase?

A

Head injury, brain tumour (same volume of gas, less space in the skull)

31
Q

What effect does increasing ICP have of cerebral perfusion pressure and therefore cerebral blood flow?

A

ICP increases
CPP decreases
Cerebral blood flow decreases
(Less perfusion, dizziness>fainting>brain damage)

32
Q

Cerebral capillaries have very tight intercellular junctions - what name is given to this obstruction?

A

Blood brain barrier

33
Q

What easily passes through the blood brain barrier?

A

Oxygen, carbon dioxide, glucose

34
Q

What is the blood brain barrier impermeable to?

A

Hydrophilic substances:

ions, catecholamines (adrenaline), protein

35
Q

The pulmonary circulation takes the __ cardiac output.

A

entire

36
Q

The airways themselves (are / aren’t) supplied by the pulmonary circulation.

A

aren’t

37
Q

Which circulation supplies airway tissue?

A

Systemic (bronchial) circulation

38
Q

How high is pulmonary resistance compared to systemic resistance?

A

Only around 10% of systemic resistance

39
Q

What are the typical values for systolic and diastolic pulmonary artery BP?

A

20-25 mm Hg (systolic)

6 - 12 mm Hg (diastolic)

40
Q

The pulmonary circulation is a __ resistance, __ pressure system.

A

low , low

41
Q

The capillary pressure in the pulmonary circulation is lower than that of the systemic capillaries - why?

A

Absorptive forces > filtration forces

Protects against pulmonary oedema

42
Q

What does the low pressure of pulmonary capillaries protect against?

A

Pulmonary oedema

43
Q

Hypoxia causes __ in the SYSTEMIC circulation.

A

vasoconstriction

44
Q

Hypoxia causes __ in the pulmonary circulation. Why?

A

vasoconstriction

V/Q mismatch - aim to divert blood from poorly ventilated lung and match again

45
Q

During exercise, skeletal muscle blood flow ___.

A

increases

46
Q

Why does skeletal muscle blood flow increase during exercise?

A
  1. Metabolic hyperaemia overcomes sympathetic tone
  2. Adrenaline causes vasodilation
  3. Cardiac output increases
47
Q

What component of veins prevents backflow of blood?

A

Valves

48
Q

Contraction of muscles aids __ __.

A

venous return

49
Q

Contraction of muscles helps blood to move through the veins (towards / away from) the heart.

A

towards

50
Q

What happens if valves in the veins become incompetent?

A

Blood pools in lower limb veins

51
Q

What is the name given to veins with incompetent valves which have acquired a pooling of blood?

A

Varicose veins

52
Q

Why don’t varciose veins reduce the cardiac output in the long term?

A

Blood volume increases to compensate

53
Q

What is metabolic hyperaemia?

A

The matching of blood flow to metabolically active tissue

54
Q

Why can metabolic hyperaemia match greater blood flow to more active tissue?

A

Metabolites (e.g CO2, adenosine, H+ and K+, etc) are all vasodilators

Cardiovascular Week 4 2016/17 (7 decks)

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