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Z-Anatomy > cardiovascular- Special circulations > Flashcards

cardiovascular- Special circulations Flashcards

1
Q

What 2 arteries arise from the base of the aorta?

A

Right and left coronary arteries

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2
Q

Where does most coronary venous blood drain?

A

Via Coronary sinus into the right atrium

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3
Q

What are special adaptations of coronary circulation?

A
  • High Capillary Density
  • High Basal Blood Flow
  • High Oxygen Extraction (~75% compared to 25% whole body average) under resting conditions
  • This means extra O2 (when required) cannot be supplied by increasing O2 extraction
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4
Q

How can extra O2 (when required) be supplied?

A

Can only be supplied by increasing coronary blood flow

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5
Q

How is coronary blood flow controlled by intrinsic mechanisms?

A
  • decreased PO2 causes vasodilatation of coronary arterioles
  • metabolic hyperaemia matches flow to demand
  • adenosine (from ATP) is a potent vasodilator
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6
Q

How is cononary blood flow controlled by extrinsic mechanisms?

A

-coronary arterioles supplied by sympathetic vasoconstrictor nerves BUT over-ridden by metabolic hyperaemia

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7
Q

Why does sympathetic stimulation of the heart result in coronary vasodilation despite direct vasoconstriction effect

A

Sympathetic vasoconstrictor nerves are over-ridden by metabolic hyperaemia as a result of increased HR and SV

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8
Q

When does peak left coronary flow occur and what does this mean?

A

diastole

- shortening diastole due to fast heart rate results in decreased coronary flow

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9
Q

When does most of coronary blood flow and myocardial perfusion occurs in diastole?

A

when the subendocardial vessels from the left coronary artery are not compressed

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10
Q

What arteries supply the brain?

A

-internal carotid arteries and vertebral arteries

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11
Q

What happens during hypoxia to the brain?

A
  • Grey matter is very sensitive to hypoxia
  • after few seconds of ischaemia consciousness is lost
  • after 3 minutes-irreversible cell damage
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12
Q

What forms the circle of willis?

A

The basilar (formed by two vertebral arteries) and the carotid arteries

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13
Q

What arises from the circle of willis?

A

major cerebral arteries

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14
Q

What causes a stroke?

A

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

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15
Q

What does autoregulation of cerebral blood flow guard against?

A

Changes in cerebral blood flow if mean arterial blood pressure changes within a range of (60-160mmHg)

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16
Q

What has little effect in the overall cerebral blood flow?

A

direct sympathetic stimulation

17
Q

Using autoregulation , what happens if MABP rises or falls?

A

rises- resistance automatically conctrict to limit blood flow
falls- resistance vessels automatically dilate to maintain blood flow

18
Q

When does auto regulation fail?

A

MABP- falls below 60mmHg or rises above 160mmHg

19
Q

When MABP drops below 50mmHg , what happens?

A

confusion
fainting
brain damage- if not quickly corrected

20
Q

What does an increase of PCO2 cause?

A

cerebral vasodilatation

21
Q

what does a decrease of PCO2 cause?

A

cerebral vasoconstriction

22
Q

What is normal intracranial pressure within the skull?

A

8-13 mmHg

23
Q

What is cerebral perfusion pressure(CPP)?

A

MAP- normal intracranial pressure (ICP)

24
Q

What causes an increase of ICP and what are the consequences?

A
  • head injury or brain tumour

- decreases CPP and cerebral blood flow

25
Q

What is the blood brain barrier?

A

cerebral capillaries have very tight intercellular junctions

26
Q

How does glucose cross the BBB?

A

facilitated diffusion using the specific carrier molecules

27
Q

What is the BBB impermeable to?

A

hydrophilic substances - ions, proteins

28
Q

Whats meets the metabolic needs of airways?

A

systemic bronchial circulation

29
Q

Why do absorptive forces exceed filtration forces?

A

protects against pulmonary oedema

30
Q

In pulmonary circulation, what affect does hypoxia have on pulmonary arterioles

A

vasoconstriction - help divert blood from poorly ventilated area in lungs

31
Q

What percentage of body mass does skeletal muscle make up?

A

40%

32
Q

why is resting blood flow low?

A

sympathetic vasoconstrictor tone

33
Q

what happens during exercise to overcome vasoconstrictor activity?

A

metabolic hyperaemia

34
Q

What does circulating adrenaline cause?

A

vasodilatation (B2 receptors)

35
Q

What does skeletal muscle pump reduced the chance of?

A

hypotension and fainting

36
Q

What is it called when blood pools in lower limb veins are caused by venous valves become incompetent?

A

Varicose veins

37
Q

why doesn’t varicose veins lead to reduction of cardiac output?

A

chronic compensatory increase in blood volume

Z-Anatomy (25 decks)

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