Introduction-Nowhere in the body is there more need forhomeostasis than in the brain.-The blood- brain barrier protects the brainagainst surging fluctuations in ion concentrations.-It is a diffusion barrier-Essential for normal function of central nervoussystem(CNS)-contains a number of key structure that carry itsimportant function
• 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 bloodfrom the brain extracellular Allow the diffusion of small fluid (BECF) in the central hydrophobic molecules (O2, nervous system (CNS). CO2, hormones) Restrict the diffusion ofProvide an optimal chemical microscopic objects (e.g., environment for cerebral bacteria) and large or function. hydrophilic molecules into the cerebrospinal fluid (CSF)
• 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 .
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
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
• 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.
• 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.
Without the BBB, undesirable molecules could freelydiffuse from the capillaries to the fluid that surrounds thebrain cells. • Poisons taken in from the Toxin environment • Upset the delicate electrochemical Ions gradients of the cerebral fluid. Acids and • Might upset the cerebral fluids bases delicate pH balance.
• 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- Alzheimers 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.