Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SMP - Cardiopulmonary Exam 1 > Lecture 17 - Special Circulations I: Coronary and Cerebral > Flashcards

Lecture 17 - Special Circulations I: Coronary and Cerebral Flashcards

1
Q

Where do epicardial coronary arteries originate from?

A

From the base of the aorta:

  • Right coronary artery from the right aortic semilunar cusp
  • Left coronary artery from the left aortic semilunar cusp
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the richest microcirculation of the CV system?

A

Coronary circulation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the collateralization of the coronary circulation.

A

If there is a blockage in one of the coronary vessels, collateral vessels will take over

These are normally closed but can become well-developed overtime as cardiovascular disease progresses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is myocardial infarction?

A

Death of tissue due to ischemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do epicardial coronary arteries give rise to?

A

Branches that penetrate both the myocardium and the endocardium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the 3 regions of the myocardium?

A
  1. Subepicardium (outermost)
  2. Middle myocardium
  3. Subendocardium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the pressure generated in the branches of the epicardial arteries in the 3 regions of the myocardium.

A

Pressures generated within each layer are different which is important when considering the perfusion of the cardiac wall, especially for the LV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do the pressures in the myocardium of the LV increase during systole? What are the implications of this?

A

Extravascular/tissue pressures increase from the subepicardium to the subendocardium => means that during systole the pressure in the subendocardium rises above 120 mmHg in order to generate the ventricular pressure => this exceeds arterial pressure and impedes perfusion of this region of the myocardium during a portion of systole => subendocardial region of LV myocardium is particularly susceptible to ischemia and infarction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Other name of epicardial coronary artery?

A

Extramyocardial coronary artery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the BP in the epicardial coronary arteries?

A

120/80 mmHg

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Are there perfusion issues in the RV myocardium during systole?

A

NOPE because much smaller pressures generated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

In which region of the myocardium intramyocardial pressure the highest during systole?

A

Subendocardium (inner third)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the flow curve of the right coronary artery.

A

Follows the aortic pressure curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the flow curve of the left coronary artery.

A
  • During isometric contraction, preceding the rise in aortic pressure, flow falls to 0 as tissue pressure rises to generate the LV systolic pressure
  • For the rest of systole flow curve follows the aortic pressure curve
  • During isometric relaxation flow greatly rises due to release of intramyocardial pressure and build up of metabolites (adenosine) during preceding systole which cause vasodilation (aka reactive hyperemia)
  • For the rest of diastole flow curve follows the aortic pressure curve
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

During what cardiac cycle phase does the greatest flow occur in the RCA?

A

Mid-systole because that is when aortic pressure is highest and there is little intervening pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

During what cardiac cycle phase does the greatest flow occur in the LCA?

A

Isometric relaxation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What metabolite is primarily responsible for reactive hyperemia in the LV during isometric relaxation and overall metabolic regulation of coronary arteries?

A

Adenosine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe myogenic regulation of coronary arteries.

A

Can be demonstrated in the coronary circulation but is less important than metabolic regulation or effects of extravascular pressure

19
Q

Describe sympathetic regulation of coronary arteries.

A

Sympathetic constriction can be demonstrated, although in normal function increased work of the heart during SNS activation results in metabolic vasodilation of coronary arteries which overrides sympathetic constriction

20
Q

When do myogenic regulation and sympathetic regulation of coronary arteries become important?

A

If the heart is diseased with flow limitations then the effects of those regulations will be much more pronounced since the heart is not working as well and not producing as many metabolites

21
Q

What is the area under the LVP curve during systole a measure of?

A

LV work and O2 demand

22
Q

What is the area under the aortic pressure curve during diastole a measure of?

A

O2 supply to the LV since the highest flow to the myocardium occurs during diastole

23
Q

What balance is important to maintain in the heart? When is this balance difficult to maintain?

A

LV O2 demand and LV O2 supply

Difficult to maintain in ill cardiac patients

24
Q

In what part of the body is the VO2 the lowest at rest? Why?

A

Heart because it is the most metabolically active organ in the body and because of the difficulty of perfusion its walls

25
Q

What are 4 factors that could tip the LV O2 supply and demand balance?

A
  1. HR
  2. Systolic arterial P
  3. Inotropic drugs
  4. Diastolic arterial pressure
26
Q

How would an increase in HR tip the LV O2 supply and demand balance?

A

Negatively

HR rises => time in systole rises/time in diastole decreases => increased O2 demand

27
Q

How would an increase in systolic arterial pressure tip the LV O2 supply and demand balance?

A

Negatively

Increased systolic arterial P = increased work done by heart => increased O2 demand

28
Q

How would inotropic drugs tip the LV O2 supply and demand balance?

A

Negatively

Increased heart contractility => increased work done by heart => increased O2 demand

29
Q

How would increasing diastolic pressure tip the LV O2 supply and demand balance?

A

POSITIVELY!

Increase diastolic P => increase flow to LV during diastole => increased O2 supply

30
Q

How can we keep diastolic pressure sufficient enough to perfuse the left ventricular wall?

A
  1. Ensure that the BV is adequate, but don’t increase it too much or else the preload will increase and the heart will have to work harder
  2. Coronary vasodilators
31
Q

How much time before fainting if blood flow to brain is occluded?

A

Seconds

32
Q

Why is cerebral circulation so tricky?

A
  • Flow occurs through a fixed volume and too much flow and pressure can cause cerebral edema which interferes with cerebral function
  • Interruption of flow for seconds disrupts neuronal function

=> need for CONSTANT global cerebral flow

33
Q

What structural component of the brain helps maintain constant global flow of blood? Explain.

A

Circle of Willis made of anastomosis of vessels going up to the brain provides collateralization of flow to respond to interruption or disturbances of cerebral blood flow

34
Q

Does the Circle of Willis look the same in all humans?

A

NOPE because when you have collateralization and redundant pathways some of them can be missing without consequences

35
Q

What is the major mechanism of control of the global cerebral blood flow?

A

Autoregulation

36
Q

In what range of pressures does autoregulation of the global CBF work? How is this range affected in chronic HT patients?

A

50-150 mmHg MAP

Chronic HT patients: higher range

37
Q

Other than through autoregulation, what other 2 mechanisms work to regulate global CBF?

A
  1. Chemical control

2. Functional vasodilation

38
Q

Describe the chemical control of global CBF. What to note?

A
  1. Levels of arterial CO2 regulate vasodilation/constriction to increase/decrease blood flow locally
    Note: this mechanism will normally be irrelevant since arterial CO2 is generally kept constant
  2. Blood levels of PaO2 below 50 mmHg => CNS ischemic reflex in response to cerebral ischemia = INTENSE SNS outflow to maintain CBF because there are no sympathetic nerve endings on cerebral vessels
39
Q

Does the chemical control of global CBF respond to PaO2 above 50 mmHg?

A

NOPE

40
Q

What is Cushing’s reflex? In what patients in this often seen? How is HR affected?

A

High intracranial pressure => poor perfusion of the brain => SNS activation to raise arterial pressure to perfuse the brain (could make the issue a lot worse, but it’s a last ditch effort)

Often seen in head trauma patients

Low HR because the baroreceptor reflex is responding to the very high arterial pressure caused by the Cushing’s reflex

41
Q

How does hyperventilation affect CBF? What does this explain?

A

Hyperventilation => decrease in CO2 levels => reduced CBF => fainting

(explains why people who are panicking breathe into a paper bag to make sure their CO2 levels do not drop and the CBF does not fall)

42
Q

Describe functional vasodilation in the cerebral circulation. What to note?

A

FUNCTIONAL VASODILATION is active in the cerebral circulation on a local level: there are differences in flow patterns in the brain during different neuronal activities due to varying O2 requirements

BUT global CBF is still constant

AND different mechanism than metabolic regulation in other organs that is much faster

43
Q

During aerobic exercise, blood flow to the left ventricular myocardium would be expected to increase, mainly due to…

A

Metabolic vasodilation

44
Q

How will aortic stenosis impact the O2 supply demand balance of the coronary circulation?

A

Negatively because decreased supply

SMP - Cardiopulmonary Exam 1 (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions