The human brain
The human brain, along with the spinal cord, constitutes its central nervous system. In a newborn, its weight does not exceed 330 or 340 grams. In the embryo stage and the first few years of childhood, the human brain is developing intensively. By the age of 20 his growth is coming to an end. In an adult male, the brain mass is 1375 g, and for a woman - 1275 g. The smaller weight of the organ in the fairer sex is due to their overall smaller size. And to old age the mass of not only all organs decreases, the brain also loses weight.
Anatomy of it, as well as functioning is studied by neurology - a discipline about the peripheral nervous system and central.
The human brain is occupied by the cranial cavity. It consists of large hemispheres and a trunk with a cerebellum.
There are five departments in the brain: it is the final brain, the middle, back, intermediate and oblong. The spinal cord has a direct relationship to the latter. The continuation of its cervical region is the medulla oblongata. Its shape resembles an elongated bulb. And the upper part of the medulla oblongata passes into the posterior one, which includes the cerebellum and the bridge. Its gray matter forms separate islets - the nucleus of cranial nerves - and not solid columns, as in the spinal cord. It also has a mesh formation due to the processes connecting the nerve cells among themselves. The bridge looks like a roller, consisting of nerve fibers. The back of it is covered with a gray substance in the form of nuclei of cranial nerves. By the end, it narrows and ends in the middle of the cerebellum, which, behind the bridge and oblong brain, closes them almost completely. Above it is covered with a gray substance and furrows is divided into lobules.
The middle brain through the isthmus is connected to the posterior one. It includes legs and quadruple. This name was given to the roof plate for dividing into two upper mounds associated with vision, and two lower ones connected with hearing. The transverse section of the midbrain represents the base of the legs of the brain, the tire and the roof. Between the legs and the roof lies the water pipe of the brain. And the tire contains a reticular formation and two large red nuclei.
Under the corpuscular body is the intermediate brain, which on the sides fuses with the large hemispheres. It has four hillocks: a visual, an overseas area, an over-the-hill and an off-shore one. The cavity of the intermediate brain is the third ventricle.
The human cerebral cortex looks like a gray substance covering the hemisphere and having a thickness of up to 5 mm. Form its nerve fibers and cells( neurons), which lie in layers in a certain order. The crust is not homogeneous. Each of its parts is characterized by the structure of fibers and cells. This is due to the functions that it performs. After all, every part of the brain takes separately impulses coming from the surface of the whole body, from tissues and organs. For example, the ways of auditory signals end in the temporal lobe, the visual - in the occipital, etc. The departments of the cortex, in turn, send impulses to its other sites, to the stem part of the brain.
In addition, the human brain, as well as the dorsal, is covered with three membranes: vascular( soft), arachnoid and solid. The porridge of the skull bones is the hard shell. On the surface of the brain passes a thin, non-articular cobweb. And the cerebral, on the contrary, contains very soft vessels, which allows it to fill all the furrows and crevices of the brain. Without it, the formation of vascular plexuses of the ventricles is impossible.
Since the spinal cord and the brain are interconnected, damage to one of them inevitably leads to disruption of reflexes, for which the other responds. The defeat of the brain and even increased fatigue, exhaustion of functions can lead to serious diseases of the central nervous system of man.