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Cardiovascular Science > Control of blood flow in differing vascular beds > Flashcards

Control of blood flow in differing vascular beds Flashcards

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1
Q

What is the coronary reserve?

A

Flow to cardiac muscle can increase 4-5x when cardiac output increases

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2
Q

What must be maintained?

A

A secure O2 supply to coronary muscle

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3
Q

What must an increased demand for O2 be met with?

A

Large increases in flow

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4
Q

How does the cardiac muscle extract the maximum amount of O2?

A

Very large a-vO2 difference

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5
Q

What are the main blood vessels of the heart?

A 
Right coronary artery
Left coronary artery
Circumflex artery
Left anterior descending branch
Posterior descending artery
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6
Q

What must be the case for blood to flow through through a coronary vessel?

A

Arterial pressure > venous pressure

Pressure inside > Pressure outside

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7
Q

When does most blood flow to the left myocardium?

A

During diastole

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8
Q

What determines flow

A

Aortic pressure during diastole

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9
Q

What is the effect of high heart rate on perfusion?

A

Reduces time

Diastole shortened

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10
Q

When is right coronary flow highest?

A

During systole

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11
Q

How is coronary flow controlled?

A

Coronary arteries exhibit myogenic autoregulation in pressure range 60-180mmHg
Some sympathetic control but overridden by local control
Metabolic hyperaemia is the dominant form of regulation

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12
Q

What is angina?

A

Decreased coronary flow due to narrowed coronary arteries

Results in pain during exercise

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13
Q

What are the consequences of not enough oxygen reaching the brain?

A

Loss of consciousness

Neuronal damage

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14
Q

What is myogenic autoregulation?

A

Ensuring O2 supply to brain tissue is maintained

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15
Q

What is the circle of Willis?

A

The name given to the connected arteries of the brain

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16
Q

What makes up the circle of Willis?

A 
Vertebral arteries
Basilar artery
Posterior cerebral artery
Posterior communicating artery
Carotid arteries
Middle cerebral artery
Anterior communicating artery
Anterior cerebral artery
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17
Q

How are the blood vessels of the brain adapted?

A

Short arterioles
Dense capillary network
Relatively high vascular resistance
Cerebral perfusion maintained if carotid artery obstructed

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18
Q

How many capillaries are in grey matter?

A

3000-4000/mm2

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19
Q

What is the blood brain barrier?

A

Cerebral capillaries form tight junctions so there is no bulk flow
No vesicular transport
Protects neurones
Maintains environment
Responsible for long lasting effects of heroine

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20
Q

What is basal flow?

A

15% of cardiac output

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21
Q

How do we protect cerebral circulation?

A

Regulating other organs

Peripheral vasoconstriction

22
Q

What is autoregulation?

A

A change in blood pressure is met by a change in resistance to maintain perfusion

23
Q

What is the autoregulatory range?

A

~60 - ~170 mmHg

24
Q

What are cerebral vessels responsive to?

A

CO2

25
Q

What is hypercapnia?

A

High blood CO2 concentration

26
Q

Why does vasodilation occur in hypercapnia?

A

Epithelial nitrous oxide

Fall in myocyte pH

27
Q

What happens in hypocapnia?

A

Low CO2
Dizziness
Cerebral arteries contract

28
Q

Why does hypoxia lead to vasodilation?

A

Adenosine
K+
Nitrous oxide

29
Q

What dose systemic hypoxia cause?

A

Hyperventilation leading to hypocapnia

30
Q

What factors couple tissue metabolism and local flow?

A

CO2
Increased interstitial K+ due to increased K+ permeability
Adenosine
Nitric oxide

31
Q

What is the maximum effect of the sympathetic nervous system on cerebral flow?

A

20-30%

32
Q

What is a cause of increased intracranial pressure?

A

Intracranial bleeding
Cerebral oedema
Tumour

33
Q

What is the result of increased intracranial pressure?

A

Collapsed veins

Decreased effective cerebral perfusion pressure reduces blood flow

34
Q

How do you calculate cerebral perfusion pressure?

A

Cerebral perfusion pressure = mean ABP - intracranial pressure

35
Q

What is an ischemic stroke?

A

Area deprived of blood

36
Q

What is a haemorrhagic stroke?

A

Area of bleeding

37
Q

What are the symptoms of vascular dilation in the brain?

A

Headaches

Migraines

38
Q

What must the cutaneous circulation be able to do?

A

Regulate body temperature

Respond to trauma

39
Q

What % of cardiac output does the skin receive?

A

10%

40
Q

Where do the capillaries sit?

A

In the dermis

41
Q

What is the structure of blood vessels in the skin?

A 
Capillaries
Vein
Venous plexus
AV anastomosis
Arteries
42
Q

What is the response to increased core temperature?

A

Increased core temperature
Removal of a-adrenoceptor mediated sympathetic tone
Cutaneous vasodilation
Heat loss

43
Q

What are AV anastomoses?

A

Found in hands, feet and face (ears, nose and lips)
50micrometre diameter with thick smooth muscle
Shunt blood from arterioles-venules
a1-adrenoceptors

44
Q

What happens to AV anastomoses when core temperature rises?

A

Dilation
Increased blood flow to venous plexus
Heat loss

45
Q

What is the result of sweating on heart rate?

A

Sweating leads to release of bradykinin a potent vasodilator
This decreases total peripheral resistance and increases heart rate
Cardiac output goes up

46
Q

What happens when core temperature falls?

A

Stimulation of a-adrenergic receptors
Vasoconstriction
Heat gain

47
Q

What is counter current exchange?

A

Radiation from warm arterial to cold venous blood flowing in opposite directions

48
Q

What is Raynaud’s disease?

A

Overreactive skin vessels
Cold/emotional stimuli leads to vasoconstriction
Skin appears white, blue, then red
Numbness, pain and burning sensation

49
Q

What is the triple response?

A

When a pointed object is drawn over skin, or a small burn

  1. White reaction - blanching due to mechanical stimulation
  2. Red reaction - local vasodilation and histamine
  3. Flare - wider intense vasodilation
  4. Wheals/ local oedema
50
Q

What nerves convey information about injury to the skin?

A

C fibre nociceptor

Cardiovascular Science (12 decks)

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