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Cardiovascular (Annie) > Special Circulations > Flashcards

Special Circulations Flashcards

1
Q

where do the right and left coronary arteries arise from?

A

arise from base of the aorta

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2
Q

where does most of the coronary venous blood drain via and into what?

A

Drains via = coronary sinus

Drains into = right atrium

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3
Q

what are 3 special adaptations does the coronary circulation have to deliver maximal O2 to myocardium?

A

1) high capillary density
2) high basal blood flow
3) high oxygen extraction (75% compared to 25% whole body average) under resting conditions

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4
Q

what does the higher oxygen extraction, in the special adaptation of coronary circulation mean?

A

means extra O2 (when required) CANNOT be supplied by increasing O2 extraction

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5
Q

how can extra O2 only be supplied to the myocardium ?

A

by increasing coronary blood flow
BECAUSE;
- the O2 extraction at the capillaries cannot be increased any further

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6
Q

how is coronary blood flow controlled?

A

1) intrinsic mechanisms

2) extrinsic mechanisms

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7
Q

in the intrinsic control of coronary blood flow, what happens to PO2 levels and what does this cause?

A

= Decreased PO2

= causing vasodilation of coronary arterioles

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8
Q

what matches coronary bloods flow to demand in the intrinsic control?

A

metabolic hyperaemia

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9
Q

what is hyperaemia?

A

increased blood flow to an organ

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10
Q

what is an example of a potent vasodilator involved in the intrinsic mechanism of coronary blood flow?

A

Adenosine (from ATP).

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11
Q

what are the coronary arterioles supplied by?

A

supplied by sympathetic vasoconstrictor nerves

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12
Q

However, why is there no vasoconstriction in the coronary arterioles then?

A

1) as the sympathetic system is over-ridden by metabolic hyperaemia
(- due to increased HR & SV)

2) causes vasodilation so heart gets increased flow

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13
Q

what is released from the adrenal gland that activates B2 adrenergic receptors causing vasodilation?

A

adrenaline

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14
Q

when does peak left coronary flow happen and why?

A

= during diastole

  • as its when the left ventricle contracts during systole the left coronary artery is also affected
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15
Q

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

A

occurs in diastole when the sub-endocardial vessels from the left coronary artery are not compressed

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16
Q

which 2 main arteries supply the brain?

A

1) internal carotids

2) vertebral arteries

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17
Q

what is grey matter?

A

darker tissue in CNS that consists of nerve cells bodies.

  • consciousness is lost after a few seconds of ischaemia, irreversible cells damage within 3minutes
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18
Q

what is grey matter very sensitive to?

A

sensitive to hypoxia

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19
Q

when is consciousness of grey matter lost?

when is irreversible cell damage done?

A

Consciousness lost
= after few seconds of ischaemia

Irreversible cell damage
= within 3 minutes

20
Q

what forms the circle of willis?

A

= BASILAR (formed by 2 vertebral arteries) & CAROTID arteries anastomoses

21
Q

what arises from the circle of willis?

A

major cerebral arteries

22
Q

how does circle of willis maintain cerebral perfusion?

A
  • even is one carotid artery gets obstructed, the others can redistribute their blood at the anastomosis
23
Q

what causes a stroke?

A

interruption/cut-off blood supply to a region of the brain

24
Q

what does auto regulation of cerebral blood flow do?

A

= gourds against changes in cerebral blood flow if MABP changes within a range (60-160mmHg)

i.e. stops flow changing even if there are changes in pressure;

25
Q

what happens to the resistance of the vessels if MABP rises?

A

vessels automatically constrict to limit blood flow.

26
Q

what happens to the resistance of the vessels if MABP falls?

A

vessels automatically dilate to maintain blood flow

27
Q

what happens if MABP falls below 50mmHg?

A
  • confusion
  • fainting
  • brain damage if not quickly corrected
28
Q

what does an increase and decrease in PCO2 do to cerebral flow?

A

Increase = causes vasodilation

Decrease = causes vasoconstriction

29
Q

what is normal intra-cranial pressure within the skull?

A

about 8-13mmHg

30
Q

what is the relationship between cerebral percussion pressure (CPP), MAP and ICP?

A

CPP = MAP - ICP

31
Q

what does increasing inter-cranial pressure, i.e. due to head injury or brain tumour, do to cerebral perfusion pressure and blood flow?

A

= decreases cerebral perfusion pressure and blood flow

32
Q

what is the blood brain barrier?

A

= very tight inter-cellular junctions at the cerebral capillaries

33
Q

what are the cerebral capillaries highly permeable to?

A

O2 and CO2

34
Q

how does glucose cross the BBB?

A

by facilitated diffusion using specific carrier molecules.

35
Q

what is the BBB impermeable to and why is this useful?

A

hydrophilic substances;
e.g. ions, catecholamines, proteins

  • useful as it protects the brain neurones from fluctuating levels of ions in the blood
36
Q

where does the entire cardiac output flow from and into?

A

flows from right ventricle into pulmonary circulation

37
Q

is the pulmonary system a high or low pressure system?

A

low

38
Q

what type of force exceeds filtration forces and what does this protect from?

A

absorptive forces

= protecting against pulmonary oedema

39
Q

does hypoxia constrict or dilate PULMONARY arterioles and why?

A

constricts them

= diverts blood away from poorly ventilated areas of lung

40
Q

True or false.

Resting blood low is low because of parasympathetic vasoconstrictor tone.

A

False.

- it is low due to SYMPATHETIC vasoconstrictor tone

41
Q

what happens during exercise in terms of vasoconstriction/dilation in skeletal muscles?

A
  • local metabolic hyperaemia overcomes sympathetic activity causing vasodilation
  • adrenaline causes vasodilation (B2 adrenergic receptors)
  • increased CO increasing skeletal muscle blood flow
42
Q

where does the skeletal muscle pump originate from? and what does contraction of these muscles aid?

A

large veins in limbs lie between skeletal muscles

= aids venous return

43
Q

what does the skeletal muscle pump reduce the chances for?

A

= postural hypotension & fainting

44
Q

what are varicose veins?

A

when valves in veins of lower limbs become incompetent and so blood pools form in them

45
Q

how does varicose veins not reduce cardiac output?

A

because there is a chronic compensatory increase in blood volume

Cardiovascular (Annie) (36 decks)

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