Neurological System IV Flashcards
What percentage of total blood volume circulates to the brain?
- 18%
What percentage of total body oxygen consumption is the brain responsible for?
- 20%
What can happen if the constant flow of oxygen to the brain is interrupted?
- Loss of consciousness
- Irreparable damage (within 5 minutes of anoxia)
What pathology occurs secondary to vascular compromise or hemorrhage in the CNS?
- Cerebrovascular disease
- 3rd-leading cause of death in the United States
Cerebral blood flow accounts for what percentage of cardiac output?
- 15-20%
What are the extracerebral vessels?
- Right carotid artery- Right subclavian
- Left carotid artery- aortic arch
What are the intracranial cerebral vessels?
- Internal carotid artery- anterior cerebral AND middle cerebral arteries
***What pair of arteries and its’ branches supply the occipital lobe and brain stem?
- Vertebral arteries- basilar artery- posterior cerebral artery
- Ultimately gives rise to circle of Willis
- In neuroanatomy, what is the confluence of vessels that give rise to all major cerebral arteries? A major component is that it provides collateral flow to the brain.
- Circle of Willis
*** The Circle of Willis is fed by what arteries?
- Internal carotid arteries
- Basilar artery
What arrangement of arteries completes the Circle of Willis?
- Posterior communicating artery on each side of the circle
- An anterior communicating artery
- Each major artery supplies a certain territory
- This means that sudden occlusion affects its’ respective territory immediately, sometimes irreversibly
- This may happen with a lesion or with direct occlusion
What does the venous drainage of the brain and coverings include?
- Veins of the brain itself
- Dural venous sinuses
- Dura’s meningeal veins
- Dipoloic veins
What is the eventual cerebral venous drainage of the brain?
- The internal jugular vein
T/F- Cerebral veins contain valves.
- False
- The cerebral veins contain no valves.
***What is the formula that derives Cerebral Perfusion Pressure (CPP)?
- CPP= MAP-ICP
- Normal CPP= 80-100 mmHg
***What is CPP primarily dependent on and what is a consequence of this?
- CPP is primarily dependent on MAP (pressure dependent)
- A consequence of this is that moderate to severe increases in ICP can significantly compromise CPP and CBF, even if MAP is normal
- ## ICP is normally below 10
What is a diagnostic change that is evident with decreased CPP?
- Changing EEG patterns
***Irreversible damage to the brain can occur is there is a sustained CPP below what value?
- 25 mmHg
- CPP less than 50 mmHg will show EEG changes
***At what CPP range is cerebral blood flow (CBF) nearly constant?
- 60-160 mmHg
- Beyond these limits, cerebral blood flow becomes pressure dependent
How does cerebral vasculature react to a decrease in CPP?
- Cerebral vasodilation
How does cerebral vasculature react to an increase in CPP?
- Cerebral vasoconstriction
***What effect does chronic arterial hypertension have on the cerebral autoregulation curve?
- Right shift
- Cerebral autoregulation curve is an “S-curve” that flattens and shows unchanged cerebral blood flow between CPP ranges of 60-160
- Long-term antihypertensive therapy is of utmost importance.
Above what CPP value si the Blood-Brain Barrier compromised and what pathologies can this cause?
- 150-160
- Cerebral edema
- Hemorrhage
***What are some extrinsic factors that autoregulation?
- Respiratory gas tensions
- CBF directly proportionate to PaCO2
- If C02 increases, cerebral blood flow increases (cerebral vasodilation)
- If C02 decreases, cerebral blood decreases (cerebral vasoconstriction) - Temperature
- CBF changes 5-7% per 1 degree C change in temperature
- Blood viscosity
- HCT-30-34 ideal for optimal CBF
- Autonomic influences
