Presentation 3

BLOOD BRAIN BARRIER(BBB)

PREPARED BY GROUP

-Nowhere in the body is there more need for homeostasis than in the brain.

-The blood- brain barrier protects the brain against surging fluctuations in ion concentrations.

-It is a diffusion barrier

-Essential for normal function of central nervous system(CNS)

-contains a number of key structure that carry its important function

Introduction

Discovery Of BBB• 1885: Paul Ehrlich: intravenous dyes in

experimental organisms caused staining of all organs except the brain

• 1913: Edwin Goldmann put forward hypothesis that the cerebral capillaries provide anatomical basis for a physiological barrier between brain and the rest of the body

• 1950s: Electron microscopy demonstrated that the outermost layers of endothelial cells in brain capillaries are fused together

Function of BBB

Separate circulating blood from the brain

extracellular fluid (BECF) in the central

nervous system (CNS).

Allow the diffusion of small hydrophobic

molecules (O2, CO2, hormones)

Provide an optimal chemical environment for cerebral function.

Restrict the diffusion of microscopic objects (e.g.,

bacteria) and large or hydrophilic molecules into the cerebrospinal

fluid (CSF)

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Permeability of BBB

Structure of BBB

Microscopic image of BBB

• The BBB exists at the level of the endothelial cells of cerebral capillaries. The endothelial cells are joined together by an extensive network of tight junctions and surrounded by a basement membrane, within which pericytes reside. Astrocytic processes (so-called end-feet) surround cerebral capillaries .

Key Structu

res

Endothelial cell

Pericytes

Astrocytes

A large, star-shaped cell found in certain tissues of the nervous system.

Have many processes One of its function is maintenance of the blood–

brain barrier

Astrocytes

one of the elongated, contractile cells found wrapped about precapillary arterioles outside the basement membrane.

Responsible for tight junction formation and vesicle trafficking amongst endothelial cells.

Open or close a given amount to allow (or disallow) certain sized particles to flow to the brain

Pericytes

Tight junction• Prevent the passage of molecules and ions

through the space between cells. • Materials must actually enter the cells (by

diffusion or active transport) in order to pass through the tissue.

• Provides control over what substances are allowed through.

Endothelial Cells• Form the walls of capillaries• The endothelial cells meet each other at what are

called tight junctions• Materials must actually enter the cells (by

diffusion or active transport) in order to pass through the tissue.

• Provides control over what substances are allowed through.

Importance of BBB

Without the BBB, undesirable molecules could freely diffuse from the capillaries to the fluid that surrounds the brain cells.

Toxin• Poisons taken in from the

environment

Ions• Upset the delicate

electrochemical gradients of the cerebral fluid.

Acids and

bases

• Might upset the cerebral fluid's delicate pH balance.

Diseases caused by a weaken, or inflammatory BBB

Diseases

Description

• 1- Menigitis is an inflammation of the membranes which surround the brain and spinal cord.

• 2- Epilepsy is a neurological disease characterized by frequent and often untreatable seizures.

• 3- Multiple sclerosis which is an auto-immune and neurodegenerative disorder. This causes the immune system attacks the myelin protecting the neurons in the central nervous system.

• 4- Neuromyelitis optica will causes these patients have high levels of antibodies against a protein called Aquaporin levels, antibodies against a protein called Aquaporin, a component of the astrocyte foot.

• 5- Sleeping sickness a condition in which trypanosoma protozoa are found in brain tissues. Parasites possibly infect the brain from the blood.

• 6- Progressive Multifocal Leukoencephalopathy is a disease in the CNS. It affects immune compromised patients usually seen with having AIDS.

• 7- De Vivo disease is a condition caused by an inadequate transport of glucose across the barrier resulting in mental retardation and other neurological problems.

• 8- Alzheimer's Disease indicate that disruption in the blood brain barrier will allow blood plasma containing amyloid beta to enter the brain and adheres preferentially to the surface of astrocytes.