Lecture 11; 9/20 Flashcards
Test 2
What is the circle of Willis?
pathway that can increase the likelihood to have collateral circulation
What does COW stand for?
Circle of Willis
When an artery get blocked in the COW what should happen?
The blood should have another pathway to get to the tissue that needs to be perfused
T/F: If you get a blockage in the COW you may not know
T
What arteries does the COW consist of?
1 Basilar arteries
3 Large arteries on each the brain:
–Posterior cerebral artery (2)
–Middle cerebral artery (2)
–Anterior Cerebral Artery (2)
Describe: Basilar artery
Anterior to the pons
midline
2 vertebral arteries combine and form 1 basilar artery
Describe: Posterior cerebral artery
2
connected to basilar artery
in the back of COW
Describe: Middle cerebral artery
2
Largest arteries in COW
In the middle on each side
Provides perfusion to the middle and lateral cerebral cortex
Bad artery to have a stroke in because it will create a massive amount of damage
Describe: Anterior Cerebral Artery
2
perfuses front and medial frontal lobe
What is A1 in COW?
Pre communicating
Early portion of the arterior cerebral artery
What is A2?
Post communicating
Late portion of the anterior cerebral artery
delivers perfusion to tissues
(extends from COW but not part of it)
What is P1 in COW?
Pre communicating
Early portion of the posterior cerebral artery
What is P2?
Post communicating
Late portion of the posterior cerebral artery
delivers perfusion to tissues
(extends from COW but not part of it)
What are the Cerebellar arteries?
Where are they?
–Around pons and brainstem–
Superior Cerebellar A
Anterior Inferior Cerebellar A
Posterior Inferior Cerebellar A
Theres 1 on each side.
2 of each.
What does the vertebral arteries feed?
The Basilar A
Posterior inferior cerebellar A
What does the Basilar A. feed?
Anterior Inferior Cerebellar A.
Posterior Cerebral A.
Superior Cerebellar A.
What does the posterior cerebral A perfuse?
Inferior parts of the brain
What is neccesary for crosstalk in the COW?
Anterior communicating artery
Located between the A2 parts of the anterior cerebral A
What is BBF?
Brain Blood Flow
Determined by metabolic requirements of brain tissues
What is the main byproduct in the brain?
CO2
Brain blood vessles open more with _____ CO2
Increase
more blood flow
What is the Autoregulation range in BBF?
50 to 150mmHg
What is the lower limit in Autoregulation of BBF? What is it called?
50 mmHg
LLA (lower limit Autoregulation)
What does Autoregulation tell us?
Systemic changes in blood pressure shouldnt change BBF unless its below a MAP or CPP of 50 or above 150
What is the upper limit in Autoregulation of BBF? What is it called?
150mmHg
ULA (upper limit Autoregulation)
How does Autoregulation work?
Blood vessles constrict and dilate to adjust
What could happen with unchecked over perfusion of BBF?
Blow up an aneurysm
What happens to BBF when MAP increases?
Blood vessels constrict to limit perfusion
What happens to BBF when MAP decreases?
Blood vessles dilate to increase perfusion
Describe Chronic HTN and Autoregulation
The Autoregulation curve will shift (LLA and ULA will be adjusted)
But will need blood vessles that can squeeze harder than normal – arteriosclerosis.
Theses blood vessles wont dilate well if your BP drops to help perfuse your brain….
large area of ischemia
wont respons to rough conditions well
What happens when theres no Autoregulation?
linear relationship between blood pressure and blood flow
What happens when a drug interfers with Autoregulation?
The horizontal line becomes a slope.
The steeper the slope the more the drug affects Autoregulation
usually not a problem. but if its a very large slope then PROBLEM
T/F: All drugs affect cerebral blood flow Autoregulation
T
What is the V-G Ca++ channel on the presynapse called?
P-Type
What does the P-Type channel do?
Allows Ca++ to flood into the motor neuron which stimulates Ach storage vessicles to move towards the NMJ for exocytosis
What is VP-2?
Ach storage vessicle thats ready for exocytosis
What is VP-1?
2nd set of Ach storage vessicles that are further up the motor neuron that aren’t quick ready for exocytosis
Not close enough to cell wall or not completely full yet
How is the P-type channel activated?
Spreading of AP down the myelinated axon of a motor neuron by fast Na+ channels
What does VP mean?
Vessicular Pool
What removes the Ca++ from the presynapse?
Ca++ ATPase pump
What is the difference between EPP and AP?
EPP = end plate potential
EPP is the initial stimulus
AP is the stimulus that follows d/t the EPP
T/F: The amount of depolarization that we get with the EPP is always enough depolarization to open Fast Na channels.
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T/F: we have TONS of extra receptors & extra neurotransmitters
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