3. Cerebral Vasculature and Brain Homeostasis Flashcards

1
Q

What are the main compositions within the skull?

A

10% CSF
10% blood/vasculature
80% brain (20% interstitial fluid, 60% intracellular fluid)

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2
Q

CSF is renewed every 6hrs and can be found in ventricles, cisterns and subarachnoid space. What are 4 of its functions?

A

cushioning
distributing secretory signals
regulating neurogensis
waste clearance

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3
Q

What does CSF do to the weight of the brain?

A

without CSF, the brain weighs as much as a toaster

with CSF, buoyancy allows the brain to float = gold ball weight

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4
Q

Choroid plexus cells make CSF. What can be found on the ventricular lumen (apical) and then blood side (basolateral)?

A

Apical: Na/K ATPase and AQP1
Basolateral: NCBE (Na dependent chloride bicarbonate exchanger) and AQP1

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5
Q

What moves water from the blood to the ventricles across the choroid plexus cells?

A

osmotic gradient

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6
Q

the Na/K ATPase creates an electrochemical gradient for Na resulting in what which creates what? *******important

A

Net flux of Na, HCO3, and Cl from blood into ventricles creating the osmotic gradient that drives H20 into ventricles via AQP1

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7
Q

What three things are greater in CSF than blood serum?

A

Cl-
CO2
pH more acidic (7.33)

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8
Q

What 3 main things are greater in serum than CSF?

A

protein
glucose
pH more basic (7.41)

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9
Q

What two things are equal after equilibration between CSF and blood serum?

A

Na and osmolarity

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10
Q

Production of CSF is constant over a wide range of intracranial pressures. Absorption of CSF is proportional to what?

A

intracranial pressure (as ICP inc, so does CSF and vice versa)

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11
Q

The brain receives 15% of cardiac output with blood flow of 750-900mL/min. What are the four main regulations of blood flow to the brain?

A

CO2 (inc in blood CO2= inc blood flow)**
[Hydrogen Ion] (inc=vasodi=inc blood)
[O2] (dec = inc blood)
Astrocyte Metabolites

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12
Q

Sympathetics leads to vasoconstriction when BP/CO increase to protect brain from surges. What are the NT/ receptors?

A

A-adrenergic via NE/ neuropeptide Y

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13
Q

Parasympathetics lead to vasodilation when CO/BP decreases to inc. blood to the brain. Via which NT and receptor? (4)

A

cholinergic via ACh, VIP, NO

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14
Q

Sensory innervation via NT SP and CGRP, which makes cerebral circulation sensitive to pain under what circumstances?

A
torsion/manipulation
decreased CSF (increases brain weight)
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15
Q

What do the following lead to… hydrocephalus, edema, infection, intracranial bleeding and tumor?

A

increased ICP

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16
Q

Increased ICP leads to obstruction of venous outflow due to compression of brain leads to what?

A

reduced arterial flow

17
Q

Autoregulation maintains blood flow in presence of changing mean arterial blood pressure. What is autoregulation mediated by?

A

sympathetic stimulation

18
Q

What occurs to allow maximal dilation or constriction?

A

max dilation: when cerebral perfusion pressure dec
Max constriction: when cerebral perfusion P inc.

Note: when CPP is normal: there will be mix of constriction and dilation

19
Q
How would each of the follow regulate cerebral blood flow?
High Pa CO2
Low O2
Acidosis
Alkalosis
A

High Pa CO2: increase CBF (cerebral blood flow)
Low O2 : Increase cbf
Acidosis: Increase CBF (to increase blood flow)
Alkalosis: Decrease CBF

20
Q

The BBB and blood-CSF barrier (with ependymal cells) are not present in what?

A

circumventricular organs (CVOs)

21
Q

The BBB and blood-CSF barrier are highly permeable to water, CO2, O2 and lipid solubles. Slight permable to Na, Cl, K and impermeable to what?

A

plasma proteins and non-lipid-soluble organic molecules

22
Q

What is the difference between the normal capillary and brain capillary?

A

brain capillary does not have slit pores/intracellular clefts. They have very tight pores to monitor substances

23
Q

What are the three main components of the BBB?

A

astrocyte endfeet
Pericytes (contract to regulate what can pass)
Endothelial cells

24
Q

There are multiple pathways across the BBB. What are the 5 things that passive diffuse?

A
H20
CO2
O2
Unbound steroid hormones
Lipid soluble stuff
25
Q

What is the main transporter for glucose from blood in the brain, which is its main energy source?

A

GLUT 1 (NOT insulin dependent)

26
Q

the Na/K/2Cl transporter transports ions from CSF to blood, its expression is tied to what two things? which are tied to what?

A

Endothelin 1 and 3 increase expression of Na/K/CC, whose production are tied to astrocyte signals

27
Q

What moves drugs that dont belong that crossed the BBB back into the blood, like a bouncer?

A

P-glycoprotein

28
Q

GLUT1 is located in astrocytes(45kD) , microvessels, choroid plexus, and ependymal cells (55kD). Where are GLUT 3 and 5 located?

A

GLUT3: Neurons
GLUT5: Microglia

29
Q

What are the first two circumventricular organs which lack BBB and what do they do?

A
  1. Posteiror pituitary - secretory- endocrine

2. Area Postrema - sensory - initiates vomitting

30
Q

What are the second two circumventricular organs which lack BBB and what do they do?

A
  1. Organum vasculosum of the lamina terminalis (OVLT) sensory-regulation of total body water and thirst
  2. Subfornical organ (SFO) - sensory