Cerebral Vasculature and Brain Homeostasis

Question 1

Fluid compartments in brain (4)

Answer 1

CSF 10%
Blood 10%
Interstitial fluid 12-20%
IC fluid 60-68%

Question 2

3 areas for CSF

Answer 2

Ventricles
Cisterns
Subarachnoid space

Question 3

Main role of CSF for brain

Answer 3

Buoyancy

Question 4

What is water from blood moved across to enter the CSF?

Answer 4

Choroid plexus

Question 5

Describe water flow across a choroid plexus cell

Answer 5

[Na+] is low inside cells. Na+ enters via NCBE. Na+ then is pumped to ventricular side via Na/K ATPase. This sets up a concentration gradient for water to flow across.

Question 6

What is the NCBE?

Answer 6

Transports Na+, HCO3- and Cl- into the cell from the blood.

Question 7

Which AQP does water flow across?

Answer 7

AQP-1

Question 8

What solute is about the same concentration in CSF and serum?

Answer 8

Na+

Question 9

What solutes are in greater concentration in CSF than serum? (3)

Answer 9

Cl-
CO2
H+

CSF is more acidic (pH 7.33)

Question 10

What is in greater concentration in serum than CSF? (3)

Answer 10

Proteins
Glucose
OH-

Serum is more basic (pH 7.41)

Question 11

What is absorption of CSF in proportion to?

Answer 11

Intracranial pressure

Question 12

What is CSF reabsorbed by?

Answer 12

Arachnoid villi

Question 13

Regulators of blood flow to the brain (4)

Answer 13

CO2 regulation
H+ conc.
O2 conc.
Astrocyte metabolites

Question 14

What is the effect of high CO2 in blood?

Answer 14

It greatly increases cerebral blood flow

Question 15

SNS NTs in cerebral circulation (2)
What is their effect?
Receptor?

Answer 15

NE and NPY.
Vasoconstriction due to increased CO or BP.
alpha adrenergic Rs.

Question 16

PSNS NTs in cerebral circulation (4)

Effect?

Answer 16

ACh, VIP, CGRP, SP.

Vasodilation due to lowered CO or BP.

Question 17

Sensory NTs in the brain (3)

Answer 17

SP, NKA, CGRP.

Question 18

How is the brain exquisitely sensitive to pain?

Answer 18

BVs are very sensitive to torsion, manipulation.

When CSF levels decrease, brain becomes heavier and movements can cause pain.

Question 19

What does pain do to blood flow in brain? Why?

Answer 19

Activates vasodilation and increases blood flow, likely to increase CSF volume.

Question 20

How does ICP effect BF?

Answer 20

Increased ICP –> obstruction of venous outflow –> reduced arterial flow.

Question 21

What can increase ICP? (5)

Answer 21

Hydrocephalus
Edema
Infection
Intracranial blockage
Tumor blockage

Question 22

What mediates autoregulation of blood flow to brain?

Answer 22

SNS

Question 23

SNS effect in brain

Answer 23

Causes vasoconstriction –> increased systemic vascular resistance.
BUT
Protects the BBB and capillaries.