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Cardiovascular Physiology > Local Control of Blood Flow > Flashcards

Local Control of Blood Flow Flashcards

1
Q

What are the two pathways that regulate the dual control of peripheral blood flow?

A

Extrinsic and Intrinsic

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2
Q

What is the primary means of extrinsic control of peripheral blood flow?

A

Nervous system (and humorally as well)

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3
Q

What are examples of pharmacologic stimuli that cause contraction of vascular smooth muscle?

A 
Catecholamines.
Endothelin.
Serotonin.
Angiotensin II.
Vasopressin
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4
Q

What are examples of pharmacologic stimuli that cause relaxation of vascular smooth muscle?

A 
Histamine.
Adenosine.
Nitric Oxide (NO).
Carbon Dioxide.
Potassium
Hydrogen ion.
Prostaglandins.
Acetylcholine.
Bradykinin.
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5
Q

How does the metabolic mechanism work?

A

Any intervention that results in an inadequate oxygen (nutrient) supply for the metabolic requirements of the tissues results in the formation of vasodilator substances which increase blood flow to the tissues.

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6
Q

What two things can cause relaxation of smooth muscle at the precapillary sphincter?

A

Lack of oxygen.

Formation of vasodilators via tissue metabolites and ions.

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7
Q

Dfine active hyperemia:

A

Increase in organ blood flow that is associated with an increased metabolic activity of that organ. Supply must equal demand.

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8
Q

Define reactive hyperemia:

A

Transient increase in organ blood flow that is associated with the period of time that that organ (or area of tissues) has become ischemic.

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9
Q

What is an example of reactive hyperemia in the clinical setting?

A

Tourniquet use for ortho cases

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10
Q

What might reactive hyperemia after tourniquet release do to the patient’s vital signs?

A

Increased Heart rate.
Increased ETCO2.
Hypotension.

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11
Q

What is typically the maximum time for tourniquet use for an ortho case?

A

2 hours

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12
Q

Would you normally see hypotension or hypertension while tourniquet in on during surgery?

A

Likely you will see hypertension.

(same volume, less space= more pressure)

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13
Q

What is autoregulation as an intrinsic control of local blood flow?

A

Intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure.

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14
Q

What are two possible explanations for autoregulation?

A

Myogenic Mechanism.

Metabolic mechanism

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15
Q

What is the theory behind myogenic mechanism of autoregulation?

A

When a lumen of a blood vessel is suddenly expanded, the smooth muscles respond by contracting in order to restore the vessel diameter and resistance.

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16
Q

What is the proposed mechanism by which smooth muscles contract in response to blood vessel expansion?

A

Stretch of vascular smooth muscle causes activation of membrane calcium channels.

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17
Q

What MAP is minimal requirement to maintain CBF?

A

MAP 55-60

18
Q

What role does the endothelium play in microcirculation?

A

Plays an active role in regulating the micrcocirculation through substances that elicit contraction or relaxation of the vascular smooth muscle.

19
Q

List the 4 (3 main) vasoactive substances released by the endothelium.

A
  1. Nitric Oxide (most important)
  2. Prostacyclin.
  3. Endothelin.
  4. Endothelial-derived hyperpolarizing factor (EDHF)
20
Q

Does smooth muscle become dilated or constricted via the endothelin pathway?

A

Contracted/Constricted

21
Q

Does smooth muscle become vasodilatedor constricted via Nitric oxide pathway?

A

Vasodilated/antiproliferation.

22
Q

Does smooth muscle become dilated or constricted via Prostacyclin pathway?

A

Vasodilated/antiproliferation.

23
Q

What is antiproliferation?

A

Inhibiting or stopping cellular growth. In terms of blood vessels, antiproliferation is the inhibition of growing the smooth muscle

24
Q

What are two examples of endothelial substances that cause antiproliferation?

A

Nitric oxide and Prostacyclin.

25
Q

What is the half life of Nitric Oxide?

A

Approx 6 seconds

26
Q

Why is the half life of nitric oxide so short?

A

Due to rapid oxidation into nitrite and nitrate. Also due to binding to hemoglobin

27
Q

Biochemically speaking, what does Nitric Oxide do in the body?

A

Increases cGMP concentration which produces relaxation by decreasing cytosolic free calcium.

28
Q

What 7 things stimulate NO production?

A 
Shearing forces acting on the endeothelium.
Angotensin II.
Acetylcholine.
Bradykinin.
Histamine.
Insulin.
Substance P.
29
Q

In addition to a potent vasodilator, Nitric oxide also provides what other functions in CV system?

A

Inhibition of platelet adhesion.
Antiproliferative.
Free radical scavenger.

30
Q

How does Nitric Oxide improve RV performance?

A

Decrease PVR.
Decrease Pulm artery pressure.
Which decreases right ventricular afterload.
Afterload goes down=RV performance gets better

31
Q

How does Nitric oxide effect V/Q relations?

A

Inhaled nitric oxide is delivered only to ventilated alveoli. This improves V/Q relations by vasodilating capillaries and improving blood flow to areas participating in gas exchange.

32
Q

What are two things that stop inhaled NO from having fully systemic effects?

A

Bind to Hgb.

Oxidizes into nitrites and nitrates.

33
Q

What does prostcyclin do to the blood vessel smooth muscle?

A

Strong vasodilator.

Inhibits platelet adhesion to the vascular endothelium.

34
Q

What does endothelin do to vessels?

A

Potent vasoconstrictor.
Increased inotropy/chrontropy.
Releases atrial natriuretic peptide.
In heart failure, contributes to calcium overload and hypertrophy (proliferative qualities)

35
Q

Which endoethelially secreted substance is implicated in pathogenesis of hypertension, vasospasm, heart failure, and pulmonary hypertension?

A

Endothelin.

36
Q

What happens when there is damage to endothelium?

A

Decrease NO and Prostacyclin.

Increased endothelin production.

37
Q

What symptoms/complications does endothelial cell damage lead to?

A

Vasoconstriction.
Vasospasm.
Thrombosis

38
Q

How is acute increase in blood flow regulation different from long-term blood flow regulation?

A

Acute increase in blood pressure will substantially increase flow through vessels; however, long-term regulation develops in the period of hours/days/weeks post acute regulation. At this point, even increase blood pressure will only flow the normal amount

39
Q

What is angiogenesis?

A

A key mechanism for long-term local blood flow regulation is to change the amount of vascularity of the tissues. For instance, if the metabolism in a tissue is increased for a prolonged period, vascularity increases.

40
Q

Who has experiences collateral circulation?

A

By age 60, most people have at least one branch of coronary vessel closure, but do not notice because of collateral blood vessels.

41
Q

What happens in a more acute event when collateral vessels are unable to form quick enough following a blockage?

A

Coronary insufficiency, serious heart attack, death.

Cardiovascular Physiology (7 decks)

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