Cerebral Vasculature and Brain Homeostasis

Question 1

What is the direction of water flow for CSF?

Answer 1

It flows from the blood side (basolateral), through the choroid plexus cell, into the ventricular lumen (apical)

Question 2

What creates the electrochemical gradient for movement of water from the blood to the ventricles across the chore plexus cells?

Answer 2

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.

Question 3

CSF and Serum have roughly equal amounts of what?

Answer 3

Na+ Osmolarity

Question 4

CSF has greater concentrations of what when compared to Serum?

Answer 4

Cl-, CO2, and is more acidic (pH is ~7.33)

Question 5

Serum has greater concentrations of what when compared to CSF?

Answer 5

Glucose, protein, and is more basic (pH is ~7.41)

Question 6

What is CSF reabsorbed by?

Answer 6

Arachnoid villi

Question 7

Is production of CSF constant over a wide range of ICP?

Answer 7

Yes

Question 8

Absorption of CSF in the arachnoid villi is proportional to what?

Answer 8

Intracranial Pressure

Question 9

What affect does increased ICP have on neurons?

Answer 9

It damages them

Question 10

What affect does increasing carbon dioxide in the blood have on cerebral blood flow? How?

Answer 10

Increased cerebral blood flow. Increased H+ concentration leads to vasodilation and therefore increased cerebral blood flow.

Question 11

What are the 4 regulators of cerebral blood flow?

Answer 11

1. ) CO2 regulation
2. ) H+ regulation
3. ) Oxygen concentration
4. ) Astrocyte metabolites

Question 12

What affect do sympathetics have on cerebral blood vessels?

Answer 12

Vasoconstriction, when systemic CO or BP increases.

Question 13

What are the neurotransmitters of sympathetics? Receptors?

Answer 13

NE and NPY

a-adrenergic receptors

Question 14

What affect do parasympathetics have on cerebral blood vessels?

Answer 14

Vasodilation when systemic CO or BP decreases

Question 15

What are the parasympathetic neurotransmitters in the brain? (4)

Answer 15

1. ) Ach
2. ) VIP
3. ) CGRP
4. ) SP

Question 16

What happens to cerebral blood flow if you increase ICP? How?

Answer 16

Decrease cerebral blood flow.

Increase ICP -> obstruction of venous outflow -> reduced arterial flow

Question 17

What can cross the BBB via passive diffusion? (5)

Answer 17

1. ) H20
2. ) CO2
3. ) Unbound steroids
4. ) O2
5. ) lipid soluble stuff

Question 18

What is the major energy source of the brain?

Answer 18

Glucose

Question 19

What channel transfers glucose across the BBB?

Answer 19

GLUT-1

Question 20

Is GLUT-1 insulin dependent?

Answer 20

No

Question 21

What is the function of the Na+, K+, 2Cl - transporter?

Answer 21

Transport ions from CSF to the blood

Question 22

What is Na+, K+, 2Cl - transporter expression tied to?

Answer 22

Endothelin 1 & 3

Question 23

What is endothelin production tied to?

Answer 23

Astrocyte signals

Question 24

What is the function of P-Glycoprotein?

Answer 24

Moves drugs that don’t belong that crossed the BBB back into the blood

Question 25

Where is GLUT 3 located?

Answer 25

Neurons

Question 26

Where is GLUT 5 located?

Answer 26

Microglia

Question 27

Where is GLUT 1 located? (4)

Answer 27

1. ) Microvessels
2. ) Astrocytes
3. ) Choroid plexus
4. ) Ependymal cells

MACE

Question 28

What are the 4 circumventricular organs?

Answer 28

1. ) Posterior pituitary - secretory
2. ) Area postrema - sensory, vomiting
3. ) OVLT - sensory, thirst
4. ) Subfornical organ - sensory

Question 29

What are the extrinsic factors that can alter cerebral blood flow?

Answer 29

1. ) Baroreceptors
2. ) Erythrocyte concentration
   
   • Anemia increases CBF
   • Polycythemia decreases CBF
3. ) Carotid vessel occlusions

Question 30

If you have a high PaCO2, what will happen to CBF?

Answer 30

It will increase

Question 31

If you have a low PaO2, what will happen to CBF?

Answer 31

It will increase

Question 32

What affect will acidosis have on CBF?

Answer 32

Increase CBF

Question 33

What affect will alkalosis have on CBF?

Answer 33

Decrease CBF