The document discusses the blood-brain barrier (BBB) and its key functions and characteristics. The BBB is formed by cerebral endothelial cells and limits molecular exchange between the blood and brain. It maintains homeostasis in the brain by regulating passage of substances like ions, nutrients, and toxins. Transport across the BBB occurs primarily through passive diffusion, carrier-mediated transport, and active transport mechanisms. The BBB and blood-cerebrospinal fluid barrier share similarities in selectively controlling molecular movement and protecting the brain microenvironment.

1. BLOOD BRAIN
BARRIER-
Characteristics,
function,transport &
similarities between
BBB and blood CSF
barrier
P. MEENALOKSHINI
II MSc Biochemistry

2. Introduction
– Blood brain barrier (BBB)- cerebral endothelium- absent - CVO.
– Limited exchange- passive diffusion.
– Capillaries-carrier mediated and active transport.

4. Characteristics of BBB
– Cerebral capillaries-birth-more permeable. BBB-early life.
– Endothelial cells- tight junction.
– Pores.
– A dense protein matrix.
– Capillaries- astrocytes.

5. Penetration of substances into the
brain
– CO2,O2, H2O-pass easily H+ & HCO3– slowly.
– Plasma proteins, organic molecules-cannot cross. Dyes, substance
bound to protein- can pass.
– Lipid soluble substances-cross more easily than water soluble
substances.
– Glucose- brain metabolism- glucose transporters.
– Ions – pass slowly.
– Bile salts & catechol- do not.

6. – Drugs( sulphonamides and erthromycin )-enter, penicillin&
chloromycetin-limited entry, anti-depressent & psychotropic
drugs-easily enter. Amines-limited entry- L-DOPA & 5-hydroxy
tryptophan – enter rapidly.
– Absence of specific transporter- limited entry.

7. Functions Of BBB
– Maintain constancy of environment-neurons- CNS- homeostatic
mechanism.
– Protection – endogenous and exogenous toxins, prevention-
neurotransmitters.
– Regulated transcellular penetration- H+ & HCO3-.
– Prevents – chemicals, permits-metabolic materials.

8. – O2,CO2,Glucose, aminoacids, electrolytes, drugs, lipid soluble
anesthetic gas-ether,NO-pass.
– Injurious chemical agents, Pathogens- cannot pass.
– Bile pigments- cannot enter,Jaundice-enter-damage basal ganglia-
Kernicterus.

9. – BBB dysfunction-abnormal neuronal activity-seizures.
– Sensor motor neurological dysfunction-reduced metabolic efficacy,
cellular damage.
– Changes in blood flow-key determinant- patho-physiology of brain
injuries.
– BBB.mp4

11. Transport of glucose & aminoacid
glu,aa.mp4
– Endothelial cells- insulin dependent glucose transporter-GLU1-
glycoprotein.
– GLU1-uptake of glucose. Regulation- cell surface GLU1 levels.
– Neuroactive substances-Aspartate & Glutamate-impermeable.
– Limited transport-paracellular barrier.
– Specific solute carriers(SLC)- glucose and aminoacids and other
nutrients.

12. Transport of Ions
– Synaptic and neuronal function-ion channels & transporters.
Water – ion channels.
– Eg- regulated ionic movement-potassium concentration- 2.5 to
2.9mM.
– If increase in conc-change in neuronal activity.
– Neuronal firing & synaptic transmission- influx of ca2+ and Na+ &
eflux of K+, neurotransmitters.

13. Transport of macromolecules
alter[Mute].mp4
– Endocytic vesicles- proteins and peptides.
– Vesicular mechanisms-RMT or AMT- transport diverse large
molecules.
Steps involved in transport
1. Internalization
2. Exocytosis
3. Interaction
Peptide specific transporter-facilitate transport.
Function- signaling cascade.

14. Transport of drugs
drugs.mp4
– Transcranial drug delivery-carrier mediated and receptor mediated
transport- facilitate transport of drugs- CNS pathologies.
– Currently- reengineering of drugs-enables BBB transport.

15. Similarities between BBB & blood
CSF barrier
– Formed –epithelium cells of brain capillaries
– Prevents & blocks -harmful chemicals- toxins- BBB & CSF.
– Substance regulation-substance transport-blood to CSF & BBB.
BBB- oxygen,CO2,glucose & aminoacids.
Chloroid plexus-calcium & endocrine substances.

16. Thank you