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MD3001 - Cardiology Physiology > 5. Vasculature: arterial blood flow and peripheral resistance > Flashcards

5. Vasculature: arterial blood flow and peripheral resistance Flashcards

1
Q

What is changed and what must be preserved in

ArtP = CO x TPR

A

TPR = changed

CO = preserved

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2
Q

What occurs in laminar fluid flow

A

Fluid molecules touching the vessel wall adhere and move more slowly due to friction. The next layer slips over these etc. Middle layers move most rapidly

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3
Q

What velocity profile is presenr during laminar flow?

A

Parabolic velocity profile

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4
Q

What is turbulent flow?

A

Occurs when a layer of laminar flow is disrputed - Increasing resistance

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5
Q

What is the purpose of Reynold’s Number (Re)

A

Used to indicate whether flow is laminar or turbulent

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6
Q

In what situations is turbulence likely?

A
  • High velocity flow
  • Large diameter vessels
  • Low blood viscosity
  • Abnormal vessel wall
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7
Q

What is blood viscosity dependent on?

A

Speed and movement of fluid; when blood stops flowing it becomes thicker

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8
Q

What are Kortkoff sounds?

A

Artificially generated turbulence

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9
Q

Explain LaPlace’s Law

A

Distending pressure (P) produces opposing forces or tension (T) in the vessel wall proportional to the radius (R) of the vessel

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10
Q

T=

A

PR

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11
Q

Tension =

A

Ability of the vessel to withstand the forces within it

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12
Q

What vessels are at high risk of turbulence?

A
  • Aorta
  • Arteriole
  • Capillary
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13
Q

How does LaPlace’s law affect blood flow?

A

Low tension required in arterioles to oppose BP. Smooth muscle = sites of tissue blood flow regulation

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14
Q

How does LaPlace’s law affect capillaries?

A

Capillaries can be extremely thin and withstand the pressure

Thin walls = essential for exchange process

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15
Q

How does LaPlace’s law affect anerysm?

A

In an aneurysm increased pressure means already weakened walls stretch eventually leading to rupture

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16
Q

What is the function of arterioles

A

Control regional distribution (where blood flows to) by local and extrinsic controls

17
Q

What is the function of metarterioles

A

Links arterioles to venules, discontinuous smooth muscle; can bypass capillary beds if required

18
Q

Prepcapillary sphincters are responsible for…

A

vasodilation produced by local factors; tap like function

19
Q

What is hyperaemia?

A

Build up of local factors and products in the tissue

20
Q

Give 4 ways the body regulates tissue blood flow

A
  • active and reactive hyperaemia
  • flow autoregulation
  • vasomotion
  • response to injury
21
Q

How does flow autoregulation work?

A

Responds to changes in arterial pressure

  • Increased ArtP = arterioles constrict to reduce flow
  • Decreased ArtP = arterioles dilate to increase flow

Also has a myogenic response; stretch activated Ca2+ channels cause reflex constriction

22
Q

Explain the function of vasomotion

A

Spontaneous oscillating contraction of blood vessels; inhert activity of smooth muscle

23
Q

What occurs in response to injury of endothelial cells?

A

Endothelin-1 released from endothelial cells causes potent vasoconstriction

24
Q

What is active hyperaemia? And give an example of where it occurs

A

If a tissue is highly active the rate of flow will increase and metabolic activity increases

E.g. skeletal muscle in exercise

25
Q

What is reactive hyperaemia?

A

When blood supply is blocked so blood flow increases to 4-7x normal

26
Q

How do endothelial cells regulate vascular tone?

A

Nitric Oxide causes dilation and relaxation of vessels. Nerves that control NO are under PSNS innervation

27
Q

Why does the body regulate total arteriolar radius?

A

Allow blood flow through capillary beds that require it

OR

larger more orchestrated role of increasing TPR by decreasing the overall arteriolar radius

28
Q

How does neural control cause vasocontriction?

A

Sympathetic nerve

29
Q

How does neural control cause vasodilation?

A

NO-releasing nerves (minimal effect)

30
Q

How does hormonal control cause vasocontriction?

A
  • Adrenaline
  • Angiotensin II
  • Vasopressin
  • (act on α1 receptors)
31
Q

How does hormonal control cause vasodilation?

A
  • Adrenaline
  • Atrial-natriuretic-peptide
  • (act on β2 receptors)
32
Q

How does local control cause vasocontriction?

A
  • Myogenic response
  • Endothelin-1
33
Q

How does local control cause vasodilation?

A
  • Decreased O2
  • K+, CO2, H+
  • Adenosine
  • Nitric Oxide
  • Bradykinin
34
Q

At rest what percentage of the total cardiac output is in the capillaries?

A

5%; blood flow is intermittent

35
Q

What controls acute regulation of local blood flow?

A

“local factors”

36
Q

What controls long term regulation of local blood flow?

A

Change in physical size and number of blood vessels

—> Angiogensis

37
Q

What is arterial pressure regulation independent to?

A

Local blood flow control or cardiac output control

MD3001 - Cardiology Physiology (10 decks)

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