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Cardio > Special Circulations > Flashcards

Special Circulations Flashcards

1
Q

Where do the right and left coronary artery arise from?

A

Base of aorta

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2
Q

How does most coronary venous blood drain?

A

Via the coronary sinus into the right atrium

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3
Q

Special adaptions of coronary circulation?

A

-High capillary density
-High basal blood flow (under resting conditions blood flow to heart is significantly higher than other tissues)
-High oxygen extraction under resting conditions
^Means extra O2 (when required) cannot be supplied by increasing O2 extraction
^Can only be supplied by increasing coronary blood flow

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4
Q

What is coronary blood flow controlled by?

A

Intrinsic and extrinsic mechanisms

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5
Q

What happens to coronary arterioles when there is decreased PO2?

A

Vasodilation

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6
Q

Coronary blood flow intrinsic mechanisms?

A 
Decreased Po2= vasodilation of coronary arterioles 
Metabolic hyperaemia (XS of blood in vessels) matches flow to demand
Adensine (from ATP) is potential vasodilator
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7
Q

Coronary blood flow extrinsic mechanisms?

A
  • Coronary arterioles supplied by sympathetic vasoconstrictor nerves BUT are over ridden by metabolic hyperaemia (by increased HR and SV)
  • Sympathetic stimulation of heart= coronary vasodilation
  • Circulating adrenaline activates B2 adrenergic receptors which= vasodilation
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8
Q

What does circulating adrenaline activate as an intrinsic mechanism?

A

B2 Adrenergic receptors= vasodilation

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9
Q

When does peak left coronary blood flow occur?

A

Diastole

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10
Q

When does most of the coronary blood flow and myocardial perfusion occur?

A

Diastole - when subendocardial vessels from the left coronary artery are not compressed**

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11
Q

What is the brain supplied by?

A

Internal carotid and vertebral arteries

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12
Q

What matter is very sensitive to hypoxia?

A

Grey matter

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13
Q

Where do major cerebral arteries arise from?

A

Circle of Willis

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14
Q

What would obstruction of a smaller branch of a main artery cause?

A

Deprive a region of the brain of its blood supply

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15
Q

What forms the circle of Willis?

A

Basilar and Carotid arteries

Basilar is formed by two vertebral arteries

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16
Q

What is stroke caused by?

A

Stroke is caused by interruption/cut-off

blood supply to a region of the brain

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17
Q

What happens if Mean arterial Blood pressure rises?

A

Resistance vessels automatically constrict to limit blood flow

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18
Q

What happens if MABP falls?

A

Resistance vessels automatically dilate to maintain blood flow

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19
Q

When does autoregulation fail?

A

If blood MABP is below 60mmHg or above 160mmHg

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20
Q

What MABP results in confusion, fainting and nbrain damage?

A

Below 50mmHg

21
Q

Why can hyperventilation lead to fainting ?

A

Increased Po2 causes vasodilation

Decreased Po2 causes vasoconstriction

22
Q

Why can hyperventilation lead to fainting ?

A

Increased Po2 causes vasodilation

Decreased Po2 causes vasoconstriction

23
Q

Percentages of brain?

A

Brain 80%
Blood 12%
Cerebral spinal fluid 8%

24
Q

Normal intracranial pressure within skull?

A

8-13mmHg

25
Q

Cerebral perfusion pressure equation?

A

CPP=MAP- ICP (intercranial pressure)

26
Q

What does increasing ICP cause? due to head injury/trauma

A

Decreased cerebral perfusion pressure and decreased cerebral blood flow

27
Q

What can some conditions which increase ICP lead to?

A

Failure of autoregulation of cerebral Blood flow

28
Q

Describe the blood brain barrier (BBB)?

A

Cerebral capillaries have very tight intercellular junctions

29
Q

Cerebral capillaries are not permeable to O2 and CO2. True or false?

A

False. Highly permeable

30
Q

How does glucose cross the BBB?

A

Facilitated diffusion using specific carrier molecules

31
Q

What is the BBB exceptionally impermeable to? How does this help the brain?

A

Hydrophillic substance- ions, catecholamines and proteins.

Helps protect brain neurones from fluctuating levels of ions etc in blood

32
Q

Where does entire cardiac output flow from?

A

Right ventricle into pulmonary circulation

33
Q

How are the metabolic needs of airways met?

A

Systemic bronchial circulation

34
Q

Special adaptions of pulmonary circulation?

A
  • Pulmonary capillary pressure is low compared to systemic capillary pressure
  • Absorptive forces exceed filtration forces
  • Hypoxia causes vasoconstriction of pulmonary arterioles
35
Q

Why is the effect of hypoxia on pulmonary circulation completely different to systemic arteriole?

A

Helps divert blood from poorly ventilated area of lung

36
Q

What does resistance of skeletal muscle vascular bed have an effect on?

A

Large impact on blood pressure

37
Q

Why is resting blood flow low?

A

Low sympathetic vasoconstrictor tone

38
Q

What happens to skeletal muscle blood flow during excercise?

A

Increases

  • Local metabolic hyperaemia overcomes sympathetic vasoconstrictor activity
  • Circulating adrenaline causes vasodilation
  • Plus increased cardiac output during exercise, these could increase skeletal muscle blood flow many folds
39
Q

What lies between skeletal muscles?

A

Large veins in limbs

40
Q

What aids venous return?

A

Contraction of muscles (skeletal muscle pump)

41
Q

What does the skeletal muscle pump aid?

A

Reduces the chance of postural hypotension and fainting

42
Q

What do one way venous valves allow?

A

Allows blood to move forward to heart

43
Q

What happes if venous valves become incompetent?

A

Blood pools in lower limb veins= varicose veins

44
Q

Why do varicose veins not usually lead to reduction of cardiac output?

A

Because of chronic compensatory increase in blood volume

45
Q

Main types of stroke?

A

Haemorrhagic stroke

Ischaemic stroke

46
Q

What guards against changes in cerebral blood flow if MABP changes within a range? what is that range

A

Autoregulation of cerebral blood flow(60-160mmHg)

47
Q

Direct sympathetic stimulation has a large effect on overall cerebral blood flow. True or false?

A

False- Very LITTLE

48
Q

Participation of the brain in the baroreceptor reflex is very little. True or False?

A

TRUE

49
Q

What is the unknown mechanism for regulation of cerebral blood flow?

A

Blood flow increases to active parts of the brain (regional hyperaemia)
This may be due to the rise in [K+]0 as a result of K+ efflux from respectively active neurones

Cardio (36 decks)

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