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Physiology II > Blood Pressure 2 > Flashcards

Blood Pressure 2 Flashcards

1
Q

What are Arterioles?

A

Part of microcirculation (connects arteries to capillaries)
Major resistance vessels
Greatest resistance to blood flow
Contribute 60% TPR
Largest pressure drop in vasculature (90mmHg to 40mmHg)

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2
Q

What are the features of Arterioles?

A

Thinner walls

Lack tunica externa

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3
Q

Large Arterioles

A

Extensive tunica media

Thin layers of smooth muscle

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4
Q

Smaller Arterioles

A

Tunica media: single layer of smooth muscle arranged spirally around endothelium

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5
Q

What are the properties of Arterioles?

A

Rich supply of sympathetic nerve fibres

Large amount of smooth muscle

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6
Q

What does radius of Arterioles depend on?

A

contraction state of the smooth muscle

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7
Q

What is the regulation of Arterioles?

A

Regulation of radius
Regulation of resistance
Regulation of BF

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8
Q

What is the function of Arterioles?

A

Control blood flow to capillary beds

Regulation of MAP

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9
Q

What is the basal vascular tone?

A

Some degree of smooth muscle contraction

Gives indication of vasodilatory capacity

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10
Q

High vascular tone

A

Large vasodilatory capacity

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11
Q

Low vascular tone

A

Low vasodilatory capacity

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12
Q

Vasodilatory

A

Dilation of blood vessels

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13
Q

What does radius (R) of a vessel strongly influence?

A

Resistance

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14
Q

What is the equation of control of radius?

A

R = 1/r^4

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15
Q

Vasoconstriction

A

Increase contraction

Decrease radius

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16
Q

Vasodilation

A

Decrease contraction

Increase radius

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17
Q

What are the 3 primary factors that determine the resistance to BF within a single vessel?

A
  1. Vessel diameter
  2. Vessel length
  3. Viscosity of blood
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18
Q

Why does the vessel diameter change?

A

Contraction and relaxation of vascular smooth muscle in wall of blood vessel

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19
Q

What controls the radius of Arterioles?

A

Intrinsic and extrinsic factors

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20
Q

What is intrinsic factors?

A

Local BF regulation

Related to metabolic needs of organ

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21
Q

What is extrinsic factors?

A

Systemic control of TPR

Closely related to MAP

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22
Q

Intrinsic factors

A

Regulating radius of Arterioles at local level

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23
Q

What are the properties of intrinsic factors?

A

Primarily chemical influences
Locally secreted chemicals
Myogenic property
Temperature

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24
Q

Primarily chemical influences

A

Metabolite changes
Match BF momentary metabolic needs
Increase BF in response to increase in metabolic activity

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25
Q

What are the components of active Hyperaemia?

A 
Increase carbon dioxide 
Increase lactic acid 
Increase H+
Increase K+
Leads to vasodilation
26
Q

What do active cells use?

A

More oxygen and fuel (glucose/fatty acid)

Need more nutrients

27
Q

What does metabolising tissue produce?

A

Carbon dioxide

28
Q

What does increase in carbon dioxide cause?

A

Smooth muscle in vessel to dilate
Blood vessels dilate
Increase BF to metabolising tissue

29
Q

What acts on arteriolar smooth muscle?

A

Decrease in oxygen

Increase in carbon dioxide

30
Q

What is the effect of vasodilation?

A

Increase blood flow

31
Q

Locally secreted chemicals (vasoactive substances)

A

Do not act directly on smooth muscle
Endothelial cells release chemical mediators
Regulate radius of Arterioles

32
Q

What are examples of vasodilator substances?

A

Nitric oxide = NO = EDRF
Histamine (inflammation on allergic reaction)
Not derived from endothelial cells
Stimulate NO release

33
Q

What are examples of vasoconstrictor?

A

Endothelin

Act on endothelial cells

34
Q

What is myogenic property?

A

Increase blood flow and increase blood pressure in Arterioles
Increase in perfusion pressure
Increase stretch of arteriolar wall

35
Q

What does contraction of smooth muscle cause?

A

Vasoconstriction

36
Q

Vasoconstriction

A

Decrease radius
Increase resistance
Decrease blood flow

37
Q

What is the purpose of myogenic property?

A

Keep blood flow constant

38
Q

Temperature

A

Heat , increase blood flow
Useful therapeutic agent
Cold, decrease blood flow
Useful therapeutic agent (reduce swelling)
Counteracts histamine induced vasodilation

39
Q

extrinsic factors

A

Regulating radius of Arteriole at systemic level
Acts to control TPR
Control the systemic vascular resistance > control MAP

40
Q

What is MAP directly proportional to

A

TPR

41
Q

What is TPR altered by?

A

Neural and hormonal mechanism

42
Q

What is neural ?

A

Sympathetic control
Sympathetic innervation smooth muscle of Arterioles
Increase sympathetic activity

43
Q

Noradrenaline

A

Released from sympathetic nerve endings

Binds to adrenergic receptors

44
Q

Noradrenaline

A

Alpha 1 receptors

Adrenal medulla20% of adrenomedullary output

45
Q

Adrenaline

A

Alpha1 and beta2 receptors
Adrenal medulla
80% of adrenomedullary output

46
Q

Vasopressin

A

Posterior pituitary gland

47
Q

Angiotensin II

A

Renin-Angiotensin-aldosterone system (RAAS)

48
Q

Vasopressin/ADH

A

Increase water reabsorption by kidneys

Causes vasoconstriction > Increase TPR

49
Q

Angiotensin II

A

Hormonal pathway - RAAS
Release of aldosterone (Na+ reabsorption)
Causes vasoconstriction
Increases TPR

50
Q

Properties of veins

A

Large diameter
Small amount of smooth muscle
Thin walls (high compliance) - less resistance to blood flow
Blood reservoir - 64% of TBV in systemic vein at rest

51
Q

Valves

A

Peripheral veins have valves
Many lie between skeletal muscles
Large veins - valves about 2-4cm apart

52
Q

Unidirectional blood flow

A

Blood only flows towards heart

53
Q

What is the function of valves?

A

Counteract gravitional effect
Minimise backflow of blood
Temporarily support columns of blood

54
Q

Venous return

A

Flow of blood back to the heart

55
Q

What factors influence venous return?

A

Blood volume (increase blood volume increase venous return)
Venomotor tone (increase venomotor tone, vasoconstriction of veins, increase venous return)
Skeletal muscle pump
Respiratory pump
Cardiac suction

56
Q

Arterial

A

High pressure
High flow velocity
Pulsatile

57
Q

Veins

A

Low pressure
Low flow velocity
Non pulsatile

58
Q

Arterioles

A

Largest drop in MAP

Site of highest vascular resistance

59
Q

Capillaries

A

Lowest velocity

60
Q

Skeletal muscle pump

A

One way valve that direct blood away from limb and towards the heart
Veins located within large muscle groups

61
Q

Skeletal muscle pump

A

Skeletal muscle contracts:
Veins compressed
Decreases venous capacity
Increases venous pressure

Exercise:
Increase muscle activity
Increase blood out of veins
Increase blood to the heart

62
Q

Cardiac suction

A

During ventricular systole, the tendinous cord pull AV valves cusps downwards, slightly expanding the atrial space and creating a slight suction that draws blood from venae cavae and pulmonary veins

Physiology II (16 decks)

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