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Hannah Neuro > cerebral vasculature and homeostasis > Flashcards

cerebral vasculature and homeostasis Flashcards

1
Q

what percent of brain fluid is CSF? blood?

A

CSF - 10%
Blood - 10%

*most is intracellular fluid at 60%

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2
Q

what are the 3 areas of CSF flow

A

ventricles
cisterns
subarachnoid space

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3
Q

functions of CSF

A
  • buoyancy
  • cushioning /protection
  • secretory signal distribution
  • regulates neurogenesis
  • waste clearance
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4
Q

what is the direction of fluid movement between blood and CSF in brain? what membrane holds the Na/K pump, NCBE, AQP?

A

-fluid flows from the blood in the capillaries into the lumen of the ventricles

apical membrane: Na/K ATPASE and AQP 1

basolateral membrane: NCBE and AQP 1

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5
Q

what creates the gradient for fluid movement into the ventricles? what is the net effect?

A

apical NA/K ATPase creates gradient that drives Na+, Cl-, and HCO3- into the ventricles which creates an osmotic gradient to bring in water into the ventricles via AQP 1

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6
Q

compare and contrast CSF and serum contents

A

CSF

  • **more acidic (lower pH)
  • more Cl-, CO2, Na+

serum

  • *more protein , glucose, basic (higher pH)
  • more K+, Ca2+, Mg 2+, and HCO3-
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7
Q

production of CSF is _____ over a wide range of intracranial pressures

A

constant

  • reabsoprtion of CSF changes based on pressure but production remains constant
  • CBF changes with ICP also
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8
Q

effects of increasing CO2 in the blood on cerebral blood flow

A

increased CO2 increases CBF

bc Carbonic anhydrase and vasodilation

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9
Q

effects of PNS and SNS innervation on cerebral blood flow

A

SNS
- increased CO or BP = vasoconstriction via Alpha adrenergic and Neurotrasnmitter NE and NPY

PNS
-decreased CO or BP = vasodilation via cholinergic receptors and neurotransmitters Ach, SP, VIP, CGRP, NO

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10
Q

describe sensory innervation effects on cerebral blood flow

A

decreased CSF causes brain to feel heavier and initiates pain via blood vessel torque

  • sensory afferents sense blood vessels and carry pain stimuli to brain
  • reciprocal activation initiates vasodilation to increase CSF via neurotransmitter CGRP, SP, NKA

*Sensory activated vasodilation

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11
Q

affects of increased intracranial pressure on cerebral blood flow

A

increased ICP –> obstruction of venous drainage –> reduced arterial blood flow (decreased CBF)

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12
Q

affects of a large increase of partial pressure of O2 in blood on CBF

A

increased Pa O2 decreases CBF

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13
Q

affects of large decrease in cerebral perfusion pressure on CBF

A
  • increases CPP increases CBF
  • decreased CPP activates vasomotor centers that sense perfusion pressure to send signals to increases systemic BP to increase blood flow to brain to increase CBF
  • mediated CBF increase by SNS vasoconstriction if increase BP is too dramatic
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14
Q

effects of increased astrocytes metabolites in blood on CBF

A

increased metabolites increased vasodilation and CBF

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15
Q

what is the affect of auto regulation in the brain interns of CBF? what regulates this activity ?

A
  • maintains CBF w/ changing BP
  • controlled with PaO2 and CPP
  • SNS mediates with vasocontriction

-maintains blood flow in presence of changing mean arterial blood pressure
(in reference too increases/decreases of PaO2 and CPP– takes a large change to make a difference on CBF)
-their concentrations will initiate changes via sensory input that will increase or decreases systemic BP
*mediated by sympathetic stimulation via vasocontriction

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16
Q

what are the sensory centers in the brain that monitor cerebral perfusion pressure

A

vasomotor centers

17
Q

affects of acidotic blood on CBF? alkalotic blood on CBF?

A

increased acidity (decreased pH) increases CBF

increased basicity (increased pH ) decreases CBF

*want to dilute acidic blood in brain

18
Q

difference between fetal and adult CSF-brain barrier

A

fetal - limited exchange between CSF and brain

adult - free exchange b/t CSF and brain

19
Q

what barrier is between blood and brain parenchyma? blood and ependymal cells of ventricles?

A
  1. Blood brain barrier -BBB

2. Blood-CSF barrier - BCB
in choroid plexus

20
Q

where is there no BBB or blood-CSF barrier in the brain ?

A

circumventricular organs

CVO

21
Q

what is highly permeable, slightly permeable, and impermeable to the BBB and BCB?

A

high- water, O2, CO2, lipid soluble
slight - Na, Cl, K (polar ions)
not- proteins, non lipid soluble organic molecules

22
Q

what is interesting of the capillaries in the brain around the BBB and BCB

A
  • lack typical slit pores around capillaries

* have tight pores that allow extra coverage and more protection

23
Q

what maintains the electrolyte composition of the CSF and brain parenchyma, excludes toxins, contains neurotransmitters, and adds protection to the brain

A

BBB

24
Q

describe the orientation of the BBB from blood to CSF

A

endothelial cells with tight junctions –> basement membrane –> astrocyte end-foot / pericytes

25
Q

function of pericyte

A

contractile cells on BBB that regulates how much can cross the BBB

26
Q

how does glucose cross the BBB

A

Glut 1 (non-insulin dependent transporter)

27
Q

what transports ions from CSF to Blood across the BBB

A

Na -K-Cl2 transporter

  • astrocytes signal endothelia production
  • this transporter related to endothelin 1 and 3 expression
28
Q

what is the function of P-gylcoprotein in the BBB

A

moves drugs/toxins that’s crossed BBB back out into the blood
*like MRP1 in GI

29
Q

where is Glut 1 / 3/ and 5 in the brain ?

A

Glut 1 - on astrocytes, micro vessels, choroid plexus, ependymal cells [BBB and BCB]

3- neurons

5- microglia

30
Q

what are the CVO organs

A
  1. posterior pituitary (ONLY secretory) - endocrine
    * 2-4 are sensory
  2. area postrema - vommiting reflex
  3. organum vasculosum of the lamina terminals (OVLT)- regulates total body water/thirst via ANG II stimulation
  4. subfornical organ - “SFO”

***since no BBB things can cross from blood to here easier

Hannah Neuro (20 decks)

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