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FHB exam one > Circulation 7 > Flashcards

Circulation 7 Flashcards

1
Q

Breakdown of coronary artery dominance in humans

A

Right-sided dominant: 50%
Left-sided dominant: 20%
Non-dominance: 30%

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2
Q

Ratio of myocardial capillaries to myocytes

A

1:1 (not usually all active simultaneously)

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3
Q

When are more myocardial capillaries likely to be recruited?

A

During episodes of ischemia

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4
Q

What is the primary determinant of coronary blood flow?

A

Aortic pressure

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5
Q

Primary regulation of coronary blood flow is due to wat?

A

Metabolic activity and changes in arteriolar resistance

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6
Q

Highest myocardial tissue pressures occur when, and what does this cause?

A

During early systole; left coronary blood flow may actually reverse during systole

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7
Q

When does maximal left coronary blood flow occur?

A

Early diastole, when tissue pressure falls to approximately 0

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8
Q

Percentages of diastolic vs systolic perfusion of myocardium

A

60-65% occurs during diastole, 25-30% during systole

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9
Q

Which layer of heart tissue is the ventricular diastolic pressure greatest?

A

In the endocardium; least near the epicardium

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10
Q

Consequences of endocardium enduring greater pressure

A

More likely to be compressed; more likely to undergo ischemic event than the epicardium

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11
Q

Regulation of endocardial vessels under normal conditions

A

Due to larger compression forces, the vessels are more dilated to accommodate

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12
Q

Diseases that can cause subendocardial infarction

A

Aortic valve stenosis
Aortic valve regurgitation
Congestive heart failure

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13
Q

Consequences of decreased coronary blood pressure

A

Endocardial blood flow will be restricted more than epicardial blood flow because of the normally greater endocardial tissue (occurs during sever hypotension or partial coronary occlusion)

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14
Q

Sympathetic adrenergic stimulation activates what receptors?

A

Alpha receptors in the coronaries, inducing weak vasoconstriction

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15
Q

Beta-1 adrenergic receptors - location in the heart and effect

A

Present on pacemaker cells and myocardium. During sympathetic stimulation, coronary vasodilation will override alpha receptors due to increases in metabolism

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16
Q

Beta-2 adrenergic receptors - location in the heart and effect

A

Coronary smooth muscle; mediate vasodilation, but are less sensitive to sympathetic stimulation

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17
Q

Vagal stimulation can be blocked by __ suggesting . . .

A

atropine; an acetylcholine effect is probably mediated by release of nitric oxide from endothelial cells

18
Q

__ is the major factor in the regulation of coronary blood flow

A

Metabolism

19
Q

Graphical relationship of coronary blood flow and myocardial metabolic activity

A

Linear relationship

20
Q

Metabolic substrates for the heart

A
  1. Fatty acids - 60%
  2. Carbohydrates - 35-40%
  3. Others (ketones, lactate, proteins)
21
Q

How is oxygen supply to the heart limited?

A

Flow-limited, because most of the oxygen (~80%) is removed from blood during its one passage through the heart

22
Q

Oxygen consumption is directly related to the __ of the heart.

A

work

23
Q

Cardiac work equation

A

Mean arterial pressure x systolic stroke volume

24
Q

__ work consumes much more oxygen than __ work

A

Pressure, volume

25
Q

Myocardial oxygen supply equation

A

Myocardial blood flow x arterial oxygen content

26
Q

Myocardial blood flow is dependent upon . . .

A

Diastolic perfusion pressure and coronary vascular resistance

27
Q

Myocardial oxygen demand depends on these three things

A

Afterload, heart rate, and contractility

28
Q

Myocardial ischemia results from this

A

An imbalance in the ratio of oxygen supply to oxygen demand, creating a relative lack of blood flow

29
Q

This is NEVER a primary cause of ischemia

A

Excessive oxygen demand

30
Q

Collateral circulation

A

Normal human heart has collateral vessels, but they are insufficient to prevent sudden infarction; can respond to gradual obstruction

31
Q

Process of gradual collateral circulation

A

Involves a complex sequence of vessel injury, inflammation, and cellular proliferation

32
Q

Coronary “steal”

A

Under certain conditions, an increase in blood flow in one region of the heart can cause a decrease in blood flow in another region

33
Q

No coronary “steal”

A

Arteriole resistance in the non-obstructed vessel vasodilates to keep the same amount of resistance in both vessels, keeping a good flow through the obstructed vessel as well

34
Q

When does coronary steal usually become an issue?

A

During exercise, when the non-obstructed vessel becomes vasodilated and the obstructed vessel remains at a higher resistance

35
Q

Clinical manifestations of coronary steal

A
  • Exercise-induced ischemia
  • Stress-testing with adenosine
  • Peripheral arterial disease that causes caludication
36
Q

How much cardiac output goes to skeletal muscle during rest?

A

20% (muscle makes up 40% of body mass)

37
Q

What is the resting flow of skeletal muscle as compared to brain and kidneys?

A

3 mL/min per 100g, compared to 50 and 400 mL/min per 100g

38
Q

What does skeletal muscle’s large flow reserve indicate?

A

Vasculature in resting muscle has a high degree of vascular tone

39
Q

What happens to the vessels with dynamic exercise?

A

Alternation between extravascular compression and free flow, but overall, there is a profound reduction in resistance to blood flow due to metabolic vasodilation

40
Q

Consequences of isometric tensions of ~70% of max or above

A

Blood flow through the contracting muscle approaches zero, so the tensions cannot be sustained for more than 1-2 min

41
Q

Innervation of skeletal muscle arteries

A

Sympathetic cholinergic receptors that induce vasodilation by acting on mucarinic receptors coupled to NO production

42
Q

Epinephrine with vascular control

A

Causes vasodilation at low concentrations through beta-2 adrenergic receptors, but at high concentrations, binds to alpha adrenergic receptors and vasoconstricts

FHB exam one (23 decks)

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