What is the “brain”?
Normally, we call the brain the organ that is protected by the skull and is responsible for collecting the signals it receives and sending the necessary orders for us to stay alive. However, the brain is only part of the system that does this job.
The correct name is the nervous system which, according to its anatomy, is divided into central and peripheral. Within the central nervous system we find the spinal cord and the brain , which in turn is made up of the brain stem, the cerebellum and now the brain .
So when we refer to the brain as the machine room where decisions are made, we are actually talking about the brain . Which is not the only one responsible for everything that happens, since without the peripheral nervous system it is nothing, because it could not receive or send information .
The central nervous system and its bone protection
The brain benefits from several structures that protect it from dangers, both physical and biochemical. The first thing that comes to mind is the skull, the set of bones that form a hard and resistant physical barrier .
This bony component is made up of eight bones creating a hollow cavity inside where the entire brain and meninges are located . The skull is capable of withstanding strong blows without suffering fractures, but this resistance is not homogeneous throughout the surface or throughout life.
The skull solidifies during the first years of life , so the brain is less protected during this period. Over the years, in old age, this protection can also diminish due to other aging factors.
Finally, the spinal cord , which is also part of the central nervous system. This structure begins at the end of the brain or brain stem and runs through the back until it reaches the sacral region, just at the end of the lumbar. The marrow also has a bony protection , since it is inside the spinal canal.
But this is not all, since all these structures have another layer of protection that is not made up of bones: the meninges .
What are the meninges?
The central nervous system has another type of protection that may seem unnecessary but has a very important function. These are the meninges, which consist of three membranes that surround the brain and spinal cord . Each layer has a special composition and properties, but together they act as a physical and chemical barrier.
The ability of the meninges to be a physical barrier lies in the cerebrospinal fluid , which is found between two membranes of the meninges and is responsible for cushioning external shocks or internal pressures .
In addition, this fluid contains many nutrients and cells that maintain and regulate the function of the spinal cord and brain. This fluid can be used to test for infection , through a lumbar puncture to remove it.
The chemical barrier of the meninges is due to the fact that the membranes also act as a filter, thus preventing the entry of pathogens . The case of meningitis, inflammation of the meninges, due to infection by viruses or bacteria, is known.
Finally, we find a structure with a very important function that must be taken into account when developing drugs for neurological diseases: the blood-brain barrier .
What is the blood-brain barrier and what is it for?
This last structure is a network of cells found in all the capillaries and blood vessels that are in contact with elements of the central nervous system. The function of this barrier is to control which molecules enter and which do not , through what we call a selective permeability.
Neurons need to receive information and nutrients from different parts of the body, however, some of them could be detrimental to the proper functioning of the brain. The blood-brain barrier works like a customs checkpoint at an airport .
Some elements such as water, gases or small molecules can cross this barrier without any problem. The largest molecules need receptors that can help them cross because they must carry out their function in the brain, as may be the case with some hormones.
The function of the blood-brain barrier is obvious: to protect from the dangers that are already inside our body , such as bacteria, viruses or even poisons. Although an infection spreads to other organs, this barrier prevents it from penetrating the brain. However, in some situations it can happen.
This protection process is very important in the development of drugs that act on neurons , since it is necessary to develop an additional mechanism that allows it to cross the customs of the blood-brain barrier. The study of the barrier has facilitated the advancement of new treatments that are specific and do not generate serious side effects, but further research is still needed to improve them.
References:
Alberts et al. 2007. Molecular Biology of the Cell. Garland Science. 5th edition.
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