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Physiology I > SCT II - Local Regulation of Circulation > Flashcards

SCT II - Local Regulation of Circulation Flashcards

1
Q

What are the types of local control of blood flow?

A
  1. Metabolic factors
  2. Active hyperemia
  3. Reactive hyperemia
  4. Myogenic autoregulation
  5. Functions of endothelium
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2
Q

What is the local control of blood flow via metabolic factors?

A

Vasodilator effect
- Hypercapnia
- Hypoxia
- pH (Acidosis)
- Adenosine
- Lactic acid
- K+
- Mg2+
- High temperature

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3
Q

What is the local control of blood flow via active hyperemia?

A

Hyperemia = excess blood

Metabolism INC
Blood flow INC

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4
Q

What is the local control of blood flow via reactive hyperemia?

A

Reactive Hyperemia = Reaction to low blood flow

due to obstruction, compensation via excess blood

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5
Q

What is the local control of blood flow via myogenic autoregulation?

A

Happens only during the autoregulatory range.

Increase in pressure will result in increase in resistance to cancel out the change, and keep flow constant

AIM - MAINTAINING CONSTANT FLOW

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6
Q

Bayliss Effect of myogenic autoregulation

A

MAP INC
↓
Stretch of vessel wall
↓
Stretch-Activated Channels
↓
Depolarization + [Ca2+]i INC
↓
Vasoconstriction
↓
Resistance INC
↓
Unchanged Q (resistance combats map increase)

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7
Q

Mention the crucial role of endothelium

A
  1. Hemostatic (pro/anti-coagulant)
  2. Growth
  3. Barrier
  4. Enzymatic metabolites
  5. Immunity & immune response
  6. REGULATION OF VASCULAR TONE (how contracted/relaxed a vessel is)
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8
Q

What stimulate the release of endothelin-1?

A
  1. Angiotensin-II
  2. ADH
  3. Thrombin
  4. Cytokines
  5. ROS
  6. Damage to endothelium
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9
Q

What happens when there is shear stress on the blood vessel?

A

Blood vessel wants to relax. How:

NO production
NO causes vasodilation in smooth m.

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10
Q

How does Bradykinin have dual function?

A

Endothelium present
Causes vasodilation

Endothelium not present
Causes contraction

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11
Q

What is the function of adrenomedullin?

A

Vasodilator

Binds to endothelium
Endothelium secretes NO & CO
NO & CO relaxes smooth muscle

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12
Q

What is the function of acetylcholine

A

PRESENCE OF ENDOTHELIUM
VASODILATOR
Binds to endothelium
Endothelium secretes NO
NO relaxes smooth m.

ABSENCE OF ENDOTHELIUM
CONTRACTOR
Binds to smooth m. directly
Causes contraction

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13
Q

What are the 4 substances that are able to induce vasodilation via endothelium but contraction of smooth muscle via absence of endothelium?

A

Acetylcholine
Histamine
Bradykinin
Serotonin

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14
Q

What’s the alias of serotonin?

A

5-Hydroxytryptamine

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15
Q

What’s the function of serotonin

A

SMALL CONC
Binds to endothelium
Endothelium release NO
NO causes vasodilation

BIG CONC
Binds directly to smooth m
Causes contraction (vasoconstriction)

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16
Q

What’s the function of thromboxane (TXA2)?

A

Vasoconstrictor, immediately binds to smooth muscle cells (bypass endothelium)

17
Q

How does the heart receive blood during diastole?

A

During systole the heart muscles are contracted and compress the vessels.

During diastole the heart muscles are relaxed and blood is able to reach the heart

18
Q

What tone is dominant in the coronaries?

A

Basal tone

19
Q

Munroe-Kaillie’s Law

A

Vskull = Vbrain + Vblood + Vcsf

CONSTANT

20
Q

Equation of cerebral perfusion pressure

A

CPP = MAP - ICP (~ 70-80 mmHg)

21
Q

What tone is dominant in the brain?

A

Basal tone

22
Q

What is the role of astrocytes?

A

Supporting cells of the brain neurons, are able to release vasodilative metabolites

23
Q

What is the role of PNS in the meninges?

A

Induces vasodilation

24
Q

How is stroke prevented via the SNS?

A

Sudden MAP increase induces SNS activation, which constricts blood vessels

25
Q

How does the lung prevent pulmonary edema?

A

Ratio of absorption is greater than that of filtration, unlike systemic circulation, where filtration is 2/3 and absorption is 1/3

26
Q

Hormones that effect pulmonary circulation and why they are special

A

OPPOSITE

Histamine - Usually VD, VC in lungs
Serotonin - Usually VD, VC in lungs
Catecholamines - Usually VD, VC in lungs

VIP, NO, ANP - Vasodilation

27
Q

Metabolite differences in pulmonary circulation

A

P[O2] DEC
P[CO2] INC
Acidosis

OPPOSITE TO SYSTEMIC - DO VASOCONSTRICTION

28
Q

Why is the reaction to metabolites different in pulmonary circulation?

A

Body assumes there’s an obstruction of an alveoli, redirecting blood to healthier alveoli, in order to be supplied with metabolites

29
Q

Explain the difference in ventilation and perfusion in the three zones of the lung

A

Zone I: V ↑ + Q ↓

Q ↑ from Zone I - III

30
Q

Which zone do bacteria prefer and why?

A

Zone I as it has lots of free oxygen

31
Q

Which zone is the lung in whilst lying-down?

A

Zone III

32
Q

Which zone should be absent in a healthy human?

A

Zone I

33
Q

What is deadspace? What is a shunt?

A

Deadspace = Good ventilation, bad perfusion

Shunt = Bad ventilation, good perfusion

Perfusion is flow

34
Q

Which tone is dominant in skeletal muscles?

A

Both basal tone and constrictor (reflex) tone

35
Q

Which tone is dominant in acral skin (thick)?

A

Only constrictor (reflex) tone

  • Has extensive capillary networks
  • Countercurrent flow
  • Sympathetic innervation
36
Q

Which tone is dominant in non-acral skin (thin)

A

Both basal tone and constrictor tone

37
Q

Which tone is dominant in kidneys?

A

Basal tone

Autoregulation - Maintaining flow
Nervous - SNS for VC for redistribution
Humoral - both VC and VD agents

38
Q

Which tone is dominant in splanchnic organs?

A

Sympathetic

VC to redistribute blood

Physiology I (15 decks)

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