Exam 2 - Lecture 6 Flashcards
CSF producing structures are surrounded by
meninges
Sinuses are named different than other veins because they are
Robust/rigid, much stronger than normal veins.
Sinus veins in brain outer layer?
dura mater
Why is a subdural hematoma a venous bleed?
Dura mater has a venous bed.
Brain blood flow rate is dependent upon
Cerebral metabolic activity.
Arterial brain blood supply that is a continous pathway
Circle of willis
What is an advantage of the circle of willis?
Increases likelihood of continuous circulation in case one gets blocked. It ensures collateral circulation.
2 vertebral arteries come together in the brain to form
Basilar artery just underneath the pons.
Posterior cerebral artery
posterior side of circle of Willis. Back/far lateral sides of brain.
Blue area on slide 23
Anterior cerebral artery
Provide perfusion for frontal lobe/ front/midline, anterior side of circle of willis.
pink area on slide 23
Middle cerebral artery
perfuse the middle and lateral parts of cerebral cortex, run lateral from circle of willis.
green area on slide 23
Largest artery from circle of willis and how it compares to the other arteries if it clots?
middle cerebral, most dangerous if it clots. If you have a stroke, middle cerebral would be worse effect.
“Early” or “Pre” or “P/A1” part of artery means its
inside the circle of willis
“Late” or “post” or P/A2” part of artery means it ___________
stems from the circle of willis
Anterior communicating artery
Connects the 2 anterior arteries off the circle of willis
Posterior communicating artery
the 2 arteries connecting posterior cerebral artery to middle cerebral arteries.
Does middle cerebral artery have a pre/post communicating artery?
no
Cerebellum is perfused through 3 major arteries:
Superior cerebellar artery, anteroinferior cerebellar artery, posteroinferior cerebellar artery.
Superior cerebellar artery branches off from
Basilar artery, for front/top of cerebellum.
Anteroinferior cerebellar artery branches from
basilar artery, perfuses the middle of cerebellum
Posteroinferior cerebellar artery stems from
each of the vertebral arteries, perfuses the back of the cerebellum.
Epidural hematoma results from
skull fractures/head trauma. Arterial bleed. Easier to fix, put in a drain and get blood out, doesnt infiltrate the rest of the brain.
Subdural hematoma bleeds from
dura mater ripping, venous bleed. Gets worse over a few days, slower to develop.
subarachnoid hemorrhage
Arterial, progresses quickly.
Aneurysm.
Messier than others, hardest to fix. When it bleeds, it infiltrates neurons/glial cells. Caused by hemorrhagic stroke, genetics, lifestyle (alcoholism, chronic hypertension)
Metabolism in the brain goes up, then _________
brain blood flow goes up
The more CO2 produced in brain, the __________ we have.
more brain blood flow
CO2 leaks into blood vessels in brain and
dilates the vessels and increases blood flow
Autoregulation
Brains abillity to adjust brain blood flow based on blood pressure.
Prevents unnecessary changes in blood flow to brain from changes in blood pressure.
autoregulation typically can regulate between what MAP?
50-150
What would brain blood flow/MAP chart look like without autoregulation?
it would be linear
If blood pressure were to raise, but the brain doesnt need more blood flow, what would happen?
Vessels in brain constrict to prevent unnecessary extra blood flow that would result from spike in blood pressure.
If blood pressure were to drop, but the brain doesnt need less blood flow, what would happen?
Vessels would dilate in order to prevent decrease in brain blood flow.
What happens if MAP dropped below 50?
Brain vessels can no longer dilate enough to increase blood flow to brain, and result in under perfusion, cell death.
What happens if MAP rised above 150?
Brain vessels can no longer constrict enough to decrease brain blood flow, resulting in overperfusion of brain. Results in aneurysms.
LLA in autoregulation
Lower limit autoregulation, usually 50 in healthy individual
ULA in autoregulation
Upper limit autoregulation, usually 150 in healthy individual
Brain can adapt to chronically high or low blood pressure by
Adjusting its upper and lower limits in autoregulation. If someones baseline MAP was 150, then the autoregulation range would be more like 100-200
What can reduce brain’s ability to autoregulate?
volatile anesthetic drugs
Chronically high blood pressure would result in
they harden up and become thick/robust vessels from having to squeeze tighter than normal to withhold the higher pressures, but the consequence is they can’t dilate as much.
What determines if a volatile anesthetic is allowed?
Measured by error bars to determine if amount of inhibition is allowed or significantly insignificant. Very difficult to measure.
Ability of a blood vessel in brain to dilate/constrict is related to
Cardiovascular health
Motor neuron in the spinal cord is located in
Anterior horn of spinal cord
Action potential moving down motor neuron in cell body has what channels?
Fast sodium channels opening and relaying AP down the axon
potassium channels as well to reset cell after AP has passed through
As well as Na+/K+ pumps to reset cell.
Once AP gets to end of neuron, it opens up
second set of VG ion channels.
The second set of VG ion channels in end of neuron that get opened up during AP are
P-type calcium channel
P-type calcium channel sees action potential and
opens up during depolarization and allow calcium to flood into the neuron.
Stimulus for the neuron to release neurotransmitter is?
Calcium coming into the neuron
Where are the neurotransmitters at the end of a neuron before they are released?
Storage vesicles next to the cell wall
ACH vesicle ready to be released into synapse
VP-2 storage vesicles
VP-1 vesicles
Not ready to be released because of their distant proximity to cell wall, or because they arent full yet. more abundant than VP-2.
How do vesicles release NT
After calcium stimulates release, vesicles fuse with cell wall and dump them in synapse/NMJ.
What shuts down the NT being excreted into synapse? There’s 4 channels.
- Ca++ pumps to pump calcium out of neuron, using ATP. Gets the vesicles to stop dumping NT.
- Na+/K+ pump are always active and everywhere to help reset, for sodium that came in during AP.
- VG K+ channels
- Calcium sensitive potassium channels are opened by calcium that came in
How many nACH receptors are on skeletal muscle surface?
millions at each NMJ, concentrated near the neurons location.
When both binding sites for ach are occupied at same time, what happens?
Channel opens up and allows sodium to flood into the cell. Ca++ may leak in as well, but not much. K+ may leak out, but not much and its blocked by sodium/calcium coming in.
Where are nACH receptors located?
On skeletal muscle at synapse near the neuron
Type of depolarization from sodium coming through nACH-r channels in skeletal muscle
End plate potential - refers to the muscle being the target.
End plate potential in healthy muscle always
Gives rise to action potential.
When does end plate potential become an action potential?
Once fast Na+ channels get involved, next to nACH-r.
The amount of depolarization we get with an end plate potential in a healthy skeletal muscle cell, will always be __________.
Enough depolarization to open fast Na+ channels and create an AP.
An end plate potential is followed by
an action potential
The current that allows AP to spread down length of skeletal muscles
Fast Na+ channels
How many receptors do you need activated for action potential
500,000.
We have way way more receptors and NTs than we really need.
