THE BLOOD-BRAIN BARRIER (BBB)
• The brain is carefully shielded from harmful changes in the blood by a
highly selective BLOOD-BRAIN BARRIER (BBB).
• It limits access of materials from the blood into the brain tissue.
• The cells that form the walls of a brain capillary, in addition to other
components, form a brier (THE BLOOD-BRAIN BARRIER)
• These cells of the brain capillary are joined by tight junctions that seal the
wall and nothing can be exchanged across the wall by passing between the
cells.
• All other substances exchanged between the blood and the brain interstitial
fluid, including such essential materials as glucose, amino acids, and ions,
are transported by highly selective membrane-bound carriers.
• Lipid-soluable substances such as O2, CO2, alcohol, and steroid hormones
can easily penetrate these cells by dissolving in their plasma membrane.
• Small water molecules also can diffuse through by passing between
phospholipid molecules of membrane or thorough Aquaporins.
• BBB protects the delicate brain from chemical fluctuations in the blood by
strictly limiting exchange between the blood and brain.
For example, if the K+ level in the blood is doubled, little change occur in
the K+ concentration of the fluid bathing the central neurons.
• The brain is carefully shielded from harmful changes in the blood by a
highly selective BLOOD-BRAIN BARRIER (BBB).
• It limits access of materials from the blood into the brain tissue.
• The cells that form the walls of a brain capillary, in addition to other
components, form a brier (THE BLOOD-BRAIN BARRIER)
• These cells of the brain capillary are joined by tight junctions that seal the
wall and nothing can be exchanged across the wall by passing between the
cells.
• All other substances exchanged between the blood and the brain interstitial
fluid, including such essential materials as glucose, amino acids, and ions,
are transported by highly selective membrane-bound carriers.
• Lipid-soluable substances such as O2, CO2, alcohol, and steroid hormones
can easily penetrate these cells by dissolving in their plasma membrane.
• Small water molecules also can diffuse through by passing between
phospholipid molecules of membrane or thorough Aquaporins.
• BBB protects the delicate brain from chemical fluctuations in the blood by
strictly limiting exchange between the blood and brain.
For example, if the K+ level in the blood is doubled, little change occur in
the K+ concentration of the fluid bathing the central neurons.
