Special Circulations: Cerebral and Pulmonary Flashcards Preview

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Flashcards in Special Circulations: Cerebral and Pulmonary Deck (45)
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1

How much of the resting cardiac output does the brain use?

15%. It is the most metabolically active tissue of the body.

2

How does the Blood Brain Barrier work?

It limits the transport of substances from the circulation into the brain, with some substances like EtOH/O2/CO2 able to cross it.

3

What are the factors that affect cerebral blood flow?

Autoregulation
Tissue Pressure
Metabolism
Neural Control

4

What is the normal cerebral perfusion pressure (CPP) of the brain?

80-100 mmHg

5

How does autoregulation affect cerebral blood flow?

If the CPP falls outside of its normal range, auto regulation will serve to correct these changes immediately.

6

If the CPP falls, how does auto regulation respond?

Cerebral vasodilation occurs to decrease the resistance in the arteries

7

If the CPP rises, how does auto regulation respond?

Cerebral vasoconstriction occurs to increase the resistance in the vessels

8

How does tissue pressure affect cerebral blood flow as CSF pressure increases?

As CSF pressure increases, veins will collapse against the pressure of the CSF but arteries will remain open due to their higher pressure. Autoregulation will dilate arteries to keep blood flow available, but flow will rapidly decrease as CSF pressure approaches arterial pressure.

9

What is the CPP equal to?

Mean Arterial Pressure - Intracranial Venous Pressure = CPP

10

What happens as intracranial pressure increases?

Vascular compression will occur

11

What is the Monro-Kellie Doctrine?

When the volume of one compartment increases, there must be a compensatory change in the volumes of the other compartments.

12

What is the equation of the Monro-Kelli Doctrine?

Brain Volume + Cerebral Vascular Volume + CSF Volume = Constant Value

13

What metabolite is the cerebral blood flow especially sensitive to?

CO2

14

As pH decreases, what happens to blood flow?

Vasodilation will occur and it will increase blood flow by decreasing the resistance.

15

As pH increases, what happens to the blood flow?

Vasoconstriction will occur and it will decrease blood flow by increasing the resistance.

16

Do changes in systemic pH affect the cerebral blood flow?

No, because H+ cannot cross the BBB easily.

17

How are pH changes in the brain occurring?

CO2 can cause pH changes as it can cross the BBB.

18

What is the effect of increased CO2 in the blood?

Vasodilation will occur and it will increase blood flow by decreasing the resistance.

19

What is the effect of decreased CO2 in the blood?

Vasoconstriction will occur and it will decrease blood flow by increasing the resistance.

20

What is the effect hyperventilation on cerebral blood flow?

It will decrease CO2 and raise the pH, therefore causing vasoconstriction leading to dizziness and fainting.

21

How does O2 affect cerebral blood flow?

Decreases in O2 can cause vasodilation, but it has much weaker effects than changes in CO2.

22

What is the effect of adenosine on cerebral blood flow?

Adenosine is formed from ATP in cases of ischemia and it causes vasodilation to increase blood flow.

23

What is the effect of K+ on cerebral blood flow?

K+ stimulates vasodilation and increases cerebral blood flow.

24

What is the effect of NO on cerebral blood flow?

NO relaxes smooth muscle via cGMP and PKG which increases Pi of myosin light chain kinase and decreases Pi of MLC. This leads to vasodilation.

25

How does the parasympathetic system affect cerebral blood flow?

Facial nerve carries some nerves to cerebral vessels and causes vasodilation.

26

How does the sympathetic system affect cerebral blood flow?

Control is weak but it increases vascular resistance via minimal vasoconstriction. The baroreceptor reflex has little effect on cerebral resistance.

27

What is Cushing's Response?

High intracranial pressure will decrease cerebral perfusion so the ischemia causes sympathetic nerve activity increase which raises systemic blood pressure. Elevation of the intracranial pressure will activate the parasympathetics in order to decrease the HR.

28

What are the signs of Cushing's Response?

High intracranial pressure
High BP
Low HR

29

What circulations do lungs have?

Pulmonary
Bronchial

30

How much of the cardiac output does the pulmonary circuit receive?

100%

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