Term
How does CO2 end up in CSF?
CO2 can affect the ________? |
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Definition
CO2 is non-polar, thus it can cross the BBB into the CSF.
Cerebral blood flow |
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Term
| What is the effect of respiratory acidosis on CBF? |
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Definition
| Hypoventilation results in an increased CO2, leading to cerebral vasodilation and increased CBF |
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Term
| How does hyperventilation affect CBF? |
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Definition
| Decreased levels of CO2 result in vasoconstriction and decreased CBF |
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Term
Looking back to the Henderson Hassel Bach equation, a rise in CO2 results in an increase in carbonic acid, which dissociates into what?
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Definition
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Term
What is the first line buffering system of hydrogen in the body?
A rise in CO2 and an increase in 2,3 DPG leads to a ___________ shift of the oxyhemoglobin curve? This causes oxygen to _______ the hemoglobin. The hemoglobin then binds _____________. |
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Definition
The RBC
right shift
leave
hydrogen |
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Term
| If CO2 levels exceed the hemoglobin's ability to buffer, CO2 will cross the BBB into the CSF. What structure detects this? What is the normal physiologic response? |
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Definition
| The central chemoreceptors. The medulla increases the respirator rate and TV in an attempt to reduce the climbing CO2 and restore a normal pH. |
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Term
What is the effect of increased CO2 on systemic circulation?
Neural circulation?
Pulmonary circulation? |
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Definition
Vasodilation
Vasodilation
Vasoconstriction |
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Term
True or false:
PaO2 has little effect on CBF unless <70 mmHg. |
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Definition
| False--little effect until < 50 mmHg. This is a protective mechanism that results in conservation of brain tissue during severe hypoxemia. Once PaO2 is less than 50, vasodilation to increase CBF results |
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Term
True or False:
1. CBF is inversely proportional to temperature.
2. CBF changes 10% for every 1 degree C change.
3. Lowering temperature reduces CMRO2 by 5-7% for every 1 degree C. |
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Definition
1. False. Directly proportional.
2. False. 5-7% change.
3. True. |
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Term
| When hearts are done under circulatory arrest, name some interventions used to preserve cerebral function. |
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Definition
| Cooling (to 15 degrees!), thiopental, steroids, mannitol, and dilantin |
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Term
What is the range of cerebral autoregulation?
What happens outside of that range? |
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Definition
50-150 mmHg
Perfusion becomes pressure dependent. |
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