The vast majority of potential drug treatments do not readily cross the barrier, posing a huge impediment to treating mental and neurological disorders. The blood–brain barrier is generally very effective at preventing unwanted substances from accessing the brain, which has a downside. This causes problems with how neurons signal to each other. In multiple sclerosis, for example, a defective blood–brain barrier allows white blood cells to infiltrate the brain and attack the functions that send messages from one brain cell (neuron) to another. It’s also thought the blood–brain barrier’s function can decrease in other conditions. As a result, the blood–brain barrier becomes more porous, allowing bacteria and other toxins to infect the brain tissue, which can lead to inflammation and sometimes death. Meningococcal bacteria can bind to the endothelial wall, causing tight junctions to open slightly. One common way this occurs is through bacterial infection, as in meningococcal disease. So what happens if the blood–brain barrier is damaged or somehow compromised? Its other function is to help maintain relatively constant levels of hormones, nutrients and water in the brain – fluctuations in which could disrupt the finely tuned environment. The purpose of the blood–brain barrier is to protect against circulating toxins or pathogens that could cause brain infections, while at the same time allowing vital nutrients to reach the brain. Surrounding the endothelial cells of the blood vessel are other components of the blood–brain barrier that aren’t strictly involved in stopping things getting from blood to brain, but which communicate with the cells that form the barrier to change how selective the blood–brain barrier is. Some larger molecules, such as glucose, can gain entry through transporter proteins, which act like special doors that open only for particular molecules.
The tight gap allows only small molecules, fat-soluble molecules, and some gases to pass freely through the capillary wall and into brain tissue. In the capillaries that form the blood–brain barrier, endothelial cells are wedged extremely close to each other, forming so-called tight junctions. Endothelial cells line the interior of all blood vessels. We now know the key structure of the blood–brain barrier that offers a barrier is the “endothelial tight junction”. While this showed that a barrier existed between brain and blood, it wasn’t until the 1960s researchers could use microscopes powerful enough to determine the physical layer of the blood–brain barrier. To his surprise, the dye infiltrated all tissues except the brain and spinal cord. The blood–brain barrier was discovered in the late 19th century, when the German physician Paul Ehrlich injected a dye into the bloodstream of a mouse. Whereas the skull, meninges and cerebrospinal fluid protect against physical damage, the blood–brain barrier provides a defence against disease-causing pathogens and toxins that may be present in our blood. As the name suggests, this is a barrier between the brain’s blood vessels (capillaries) and the cells and other components that make up brain tissue. Both provide further defence against physical injury.Īnother protective element is the blood–brain barrier. The most obvious is our 7mm thick skull, but the brain is also surrounded by protective fluid (cerebrospinal – of the brain and spine) and a protective membrane called the meninges. The brain is precious, and evolution has gone to great lengths to protect it from damage.
0 kommentar(er)
