Makeup and function of the blood brain barrier.
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Makeup and function of the blood brain barrier
The makeup
The Blood-Brain Barrier (BBB) is a physical part of the brain that acts as a barrier to prevent large molecules from entering the brain. These molecules tend to have a potentiality of being toxic, and that is why they must be restricted to protect the brain. The barrier is made to separate the central nervous system and the systematic circulation. The structure of this barrier is made by several tight junctions that are between the endothelial cells of the brain (Murphy, 2017). Apart from the endothelial cells, the blood-brain barrier is also made up of other components. These components include microglia, pericytes, and a basement membrane that is structured by proteins like extracellular matrix.
The pericytes are made in a way that they can contract so that they can control the flow of blood in the capillaries. There is also part of the brain called brain parenchyma, which the barrier protects from the diffusion of molecules and other bacteria. Research has shown that there are some parts of the brain; we do not have a blood-brain barrier. The importance of this is that it allows the brain to control and monitor any homeostatic changes that occur within the systematic circulation (Murphy, 2017). The blood-brain barrier consists of several different barriers that are structure to work parallel to each other in various anatomical regions. Some of the barriers that have been studied are vascular and choroid barriers. The endothelial cells have mechanisms that enable these main barriers to function well. The endothelial is supported by Astrocytes that are found in the brain and the spinal cord. Each is structured to restrict the movement of solutes in the brain. The blood-brain barrier also extends all through into the central nervous system
The function
The blood-brain barrier is structured to be semi-permeable so that it can only allow some materials and prevent some from crossing. Some of these materials or particles are large and cannot pass through the blood-brain barrier easily. Molecules that are prone to high electric charges are also slowed down by BBB. In this way, the BBB can protect the brain from any harmful substances that can result in injuries (Nangia, 2020). It can protect the brain from neurotransmitters and certain hormones that are found in the rest of the body. The BBB achieves this by ensuring and maintaining an environment that is constant for the brain to function well. It also helps in maintaining levels of water and nutrients in the brain and keeps them at a constant level to avoid fluctuations that can cause disruption.
In some parts of the brain, like in the circumventricular organs, the blood-brain barrier is made to be weak. This has its advantages. It allows some molecules to cross in the brain freely, and therefore the brain can monitor the makeup of the brain (Nangia, 2020). The BBB is also responsible for transporting some toxic substances back into circulation. If the BBB functions well, it ensures that the brain circuits are working correctly. The availability of pericytes enables the blood-brain barrier to play its essential role in regulating the functions of neurovascular. Pericytes are also very crucial because they form and maintain the permeability of the blood-brain barrier during adulthood and when one is aging. If there is any deficiency in pericytes, the blood-brain barrier might be unable to function well.
References
Murphy, E. (2017). The blood-brain barrier and protein-mediated fatty acid uptake: the role of
the blood-brain barrier as a metabolic barrier. Journal Of Neurochemistry, 141(3), 324-329. https://doi.org/10.1111/jnc.14000
Nangia, S. (2020). The Blood-Brain Barrier: More than Just a Barrier. Scientia.
https://doi.org/10.33548/scientia490