Cerebral Vasculature and Brain Homeostasis Flashcards
What is the direction of water flow for CSF?
It flows from the blood side (basolateral), through the choroid plexus cell, into the ventricular lumen (apical)
What creates the electrochemical gradient for movement of water from the blood to the ventricles across the chore plexus cells?
Na+ K+ ATPase in the apical membrane creates a gradient for Na+.
A flux of Na+, HCO3+, and Cl- crosses into the choroid plexus cell via a NCBE transporter. This creates the osmotic gradient that drives water into the ventricles.
CSF and Serum have roughly equal amounts of what?
Na+ Osmolarity
CSF has greater concentrations of what when compared to Serum?
Cl-, CO2, and is more acidic (pH is ~7.33)
Serum has greater concentrations of what when compared to CSF?
Glucose, protein, and is more basic (pH is ~7.41)
What is CSF reabsorbed by?
Arachnoid villi
Is production of CSF constant over a wide range of ICP?
Yes
Absorption of CSF in the arachnoid villi is proportional to what?
Intracranial Pressure
What affect does increased ICP have on neurons?
It damages them
What affect does increasing carbon dioxide in the blood have on cerebral blood flow? How?
Increased cerebral blood flow. Increased H+ concentration leads to vasodilation and therefore increased cerebral blood flow.
What are the 4 regulators of cerebral blood flow?
- ) CO2 regulation
- ) H+ regulation
- ) Oxygen concentration
- ) Astrocyte metabolites
What affect do sympathetics have on cerebral blood vessels?
Vasoconstriction, when systemic CO or BP increases.
What are the neurotransmitters of sympathetics? Receptors?
NE and NPY
a-adrenergic receptors
What affect do parasympathetics have on cerebral blood vessels?
Vasodilation when systemic CO or BP decreases
What are the parasympathetic neurotransmitters in the brain? (4)
- ) Ach
- ) VIP
- ) CGRP
- ) SP
What happens to cerebral blood flow if you increase ICP? How?
Decrease cerebral blood flow.
Increase ICP -> obstruction of venous outflow -> reduced arterial flow
What can cross the BBB via passive diffusion? (5)
- ) H20
- ) CO2
- ) Unbound steroids
- ) O2
- ) lipid soluble stuff
What is the major energy source of the brain?
Glucose
What channel transfers glucose across the BBB?
GLUT-1
Is GLUT-1 insulin dependent?
No
What is the function of the Na+, K+, 2Cl - transporter?
Transport ions from CSF to the blood
What is Na+, K+, 2Cl - transporter expression tied to?
Endothelin 1 & 3
What is endothelin production tied to?
Astrocyte signals
What is the function of P-Glycoprotein?
Moves drugs that don’t belong that crossed the BBB back into the blood
Where is GLUT 3 located?
Neurons
Where is GLUT 5 located?
Microglia
Where is GLUT 1 located? (4)
- ) Microvessels
- ) Astrocytes
- ) Choroid plexus
- ) Ependymal cells
MACE
What are the 4 circumventricular organs?
- ) Posterior pituitary - secretory
- ) Area postrema - sensory, vomiting
- ) OVLT - sensory, thirst
- ) Subfornical organ - sensory
What are the extrinsic factors that can alter cerebral blood flow?
- ) Baroreceptors
- ) Erythrocyte concentration
- Anemia increases CBF
- Polycythemia decreases CBF
- ) Carotid vessel occlusions
If you have a high PaCO2, what will happen to CBF?
It will increase
If you have a low PaO2, what will happen to CBF?
It will increase
What affect will acidosis have on CBF?
Increase CBF
What affect will alkalosis have on CBF?
Decrease CBF
