Blood brain barrier

Question 1

Name the brain areas lacking a BBB

Answer 1

Circumventricular organs

• Area postrema- chemoreceptor- vomiting
• Post pituitary- hormones released have direct access to circulation
• Median eminence- oxytocin, vasopression. Pick up releasing hormones for carriage to the ant pituitary
• OVLT- organ vasculosum of lamina termalis- actions of cytokines in the periphery- fever

Question 2

Describe the effects of tumours on the BBB

Answer 2

Leaky BBB

increased nutrients, increased growth

Question 3

Describe the effect of infiltration

Answer 3

Infection

Increased antibiotic permeability

Question 4

Describe the effect of ischaemia

Answer 4

Cellular damge

Increased water, oedema

Question 5

Why can’t dopamine cross the BBB?

Answer 5

Ionised at ph 7.4

Question 6

Which factors regulate passage through the BBB?

Answer 6

Lipid solubility increases, access increases
Plasma protein binding– to large
Ionisation at ph 7.4–less acess

Question 7

Name 3 lipid soluble molecules

Answer 7

L leucine
D glucose
L DOPA

Question 8

Why can’t anti epileptics cross?

Answer 8

Plasma protein bound– lower uptake

Question 9

How is glucose transported?

Answer 9

D glucose transported via GLUT1, not metab by brain, taken up mark cell activity- PET
Essential aa transported, not transporters

Question 10

Define BBB

Answer 10

CNS needs ultrastable environment
Altered if ECF composition is altered
Morphological factors and mechanisms reg transport across brain capillary endothelial cells
Tight junctions between endo cells 
Restricts mW>2000 eg proteins

Question 11

Describe the clinical use of CSF

Answer 11

Spinal block to anesthesise spinal nerves distal to site of application- intrathecal drug application
Routine procedure
Injection into third ventricle, unlimited access to ECF so neurones and glia. not routine

Question 12

Describe lumbar puncture

Answer 12

Sampling of CSF for detection of pathogens eg MS, meningitis
Measure CSF pressure for detection of hydrocephalus, sub arachnoid haemorrhage
Routine clinical procedure L3-5

Question 13

List the routes of drainage of CSF

Answer 13

Bulk flow via arachnoid villi
Diffusion- vascular epi
AT- choroid plexus eg weak organic acids

Question 14

Describe the composition of CSF

Answer 14

Low protein, cholesterol, K+

Question 15

Describe the mechanism of CSF secretion

Answer 15

Basolateral- neutralise weak acids from CNS- H+/Na+ in, HCO3- accum, leaves, Cl- in

Apical membrane- Na+ out/K+ in
HCO3- and CL- leave- KCC4 transport
AQP1- water transporter

Question 16

Describe the two processes of CSF secretion

Answer 16

• Choroid epi cells secrete fluid into ventricles

- Ultrafiltration of plasma across fenestrated capillary wall into ECF beneath basolateral membrane of choroid epi cell

Question 17

Outline CSF movements

Answer 17

Lateral ventricles- cortex
Foramina of Monroe
3rd ventricle- Thalamus
Cerebral aqueduct of Sylvius
Fourth ventricle- brain stem
Two foraminae of Luschka and Magendie
Subarachnoid space

Question 18

List 8 functions of cerebrospinal fluid

Answer 18

Cushion, shock absorber
Appropriate environment for glial cells/neurones
Exchange medium- ECF and blood
Waste removal- drugs, NT, metabolites
Fills ventricles- thin layer, around brain and SC
Interface between brain and peripheral endo functions
150 mls, 500mls a day
CSF secretion pushes CSF- SA space

Question 19

Describe the blood CSF barrier

Answer 19

CSF- filtrate of blood made in choroid plexus of ventricles- around brain and sc
Arachnoid gran-CSF- venous sinuses- systemic circulation
Nutrient transfer and waste removal

Question 20

Describe ECF

Answer 20

Interacts with CSF, neuronal cells, glia. Solute conc fluctuates with neuronal activity
CSF affects composition
BBB prodects ECF from fluctuations in conc, limit compound entry
Glial cells (astrocytes) condition ECF