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NS-1 > Cerebral Vasculature and Brain Homeostasis > Flashcards

Cerebral Vasculature and Brain Homeostasis Flashcards

1
Q

What are the 4 main fluid compartments of the brain?

A
  1. CSF = 10%
  2. blood = 10%
  3. IF = 12-20%
  4. Intracellularfluid = 60-80%
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2
Q

How much CSF is there and how often is it renewed?

A

~150 mL

renewed every ~ 6 hrs (550 mL/day)

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3
Q

What are the 3 areas CSF lives?

A

ventricles
cisterns
subarachnoid space

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4
Q

How does CSF help the brain?

A

creates bouyancy

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5
Q

How does water flow through choroid plexus epithelial cells?

A

from blood (basolateral side) to ventricular lumen (apical)

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6
Q

What transporters are on the apical membrane of choroid plexus cells?

A

Na/K-ATPase

aquaporin

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7
Q

What transporters are on the basolateral/blood side of choroid plexus cells?

A

NCBE

aquaporin

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8
Q

How do choroid plexus cells move water from the blood to ventricles?

A

Na/K-ATPase creates electrochemical gradient for Na –> net flux of Na, HCO3 and Cl- into ventricles
water follows via osmosis

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9
Q

What type of aquaporin is in choroid plexus cells?

A

AQP 1

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10
Q

What things are in the same concentration in CSF and serum?

A

Na

osmolarity

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11
Q

What things are found in greater concentration in CSF compared to Serum?

A

Cl-
CO2
H+ (pH is more acidic)

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12
Q

What things are found in greater concentration in serum than CSF?

A 
Protein*
glucose*
(pH more basic)
K+
Ca
Mg
HCO3
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13
Q

How are absorption of CSF and intracranial pressure related?

A

absorption of CSF is proportional to ICP
ICP < 68 mm Hg, no absorption occurs
normal = 112

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14
Q

How does blood CO2 affect cerebral blood flow?

A

increased CO2 in blood greatly increases cerebral blood flow

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15
Q

What is normal cerebral blood flow?

A

750-900 mL/min

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16
Q

How do sympathetics and parasympathetics affect cerebral circulation?

A

Sympathetics: vasoconstriction when CO or BP increases
Parasympathetics: vasodilation when BP decreases (get more blood to the brain)

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17
Q

What NTs and receptors do sympathetics use to alter cerebral circulation?

A

NE and NPY

alpha adrenergic

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18
Q

What NTs do parasympathetics use to alter cerebral circulation?

A

Ach
VIP
CGRP
SP

19
Q

How are cerebral vessels innervated?

A

very sensitive to torsion/manipulation –> pain

decreased CSF vol –> brain heavier –> pain

20
Q

How does ICP affect cerebral blood flow?

A

increased ICP –> obstruction of venous outflow –> reduced arterial flow

21
Q

How are Pa O2 and cerebral blood flow related?

A

as O2 increases –> flow decreases steeply at first –> plateaus at 50 mL/100 g/min

22
Q

How are cerebral perfusion pressure and cerebral blood flow related?

A

increase together steeply at first –> blood flow plateaus at about 50 mL/100 g/min
will then increase again if perfusion pressure gets above 200

23
Q

What mediates autoregulation?

A

sympathetic stimulation

24
Q

What is the purpose of vasoconstriction?

A

increases systemic vascular resistance
BUT
protects the BBB and capillaries

25
Q

What occurs in the result of reduces brain perfusion?

A

activates vasomotor centers –> increased systemic BP –> drives blood to the brain

26
Q

How do acidosis and alkalosis affect CBF?

A

acidosis –> increases CBF

alkalosis –> decreases CBF

27
Q

Where is the BBB not present?

A

circumventricular organs (CVOs)

28
Q

What is the BBB highly permeable to?

A

CO2
O2
lipid-soluble substances

29
Q

what is the BBB slightly permeable to?

A

Na
Cl
K+

30
Q

What is the BBB nearly impermeable to?

A

plasma proteins

non lipid soluble organic molecules

31
Q

What things surround the capillaries of the brain?

A

endothelial cells
pericytes
smooth muscle
astrocyte end feet

32
Q

What things move via trancellular pathway through BBB?

A

lipid soluble agents

33
Q

What transporter moves glucose across the BBB?

A

Glut 1
NOT insulin-dependent
2 forms: 45 kD, 55 kD

34
Q

What does the NKCC do in the BBB?

A

transports ions from CSF to blood
tied to endothelin 1 and 2
endo production tied to astrocyte signals

35
Q

What is P-glycoprotein?

A

moves drugs that don’t belong from brain back into blood

36
Q

Where is glut 3?

A

neurons

37
Q

Where is glut 5?

A

microglia

38
Q

Where is the 45 kD form of glut 1 found?

A

astrocytes

39
Q

Where is 55 kD form of glut 1 found?

A

microvessels
choroid plexus
ependymal cells

40
Q

What are the CVOs?

A

secretory: post pit
sensory:
area postrema
OVLT
subfornicular organ

41
Q

What is the area postrema?

A

sensory CVO

initiation of vomiting in response to chemotactic triggers

42
Q

What is the organum vasculosum of the lamina terminalis (OVLT)?

A

sensory CVO
regulation of total body water and thirst
*target of angiotensin II

43
Q

What is the subfornicular organ?

A

sensory CVO

NS-1 (50 decks)

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