The brain with more than 100,000 million interconnected neurons is the control center of the nervous system. The main part of the brain, the brain, processes and sends nerve signals, which allows us to relate to the environment, move in coordination, think, create, learn and be alert.
The two hemispheres of the brain, left and right, control respectively the opposite side of the body. Other brain areas are responsible for the automatic control of functions such as breathing and blinking, as well as the vigor and frequency of the heart rhythm.
The brain, of which we see a vertical section, has three basic regions: the forebrain, the cerebellum and the brainstem. The forebrain is formed by the two hemispheres, which constitute 85% of the brain mass and, below, the thalamus and the hypothalamus. The cerebellum coordinates movement and balance. The brainstem connects the brain with the spinal cord and controls vital processes, such as breathing. The brain is protected by three membranes, called meninges, and the skull.
The thin outer layer of each hemisphere, the cerebral cortex, processes and stores information and initiates the movements of the body. The different zones of the cortex perform specific tasks, as we see in this map of the left hemisphere, but they never operate isolated.
The sensor areas (S) receive information from the sensors, for example, from the skin. The motor zones (M) send instructions to the muscles. About 75% of the cortex consists of association zones (A). They interpret and analyze the information and allow us to learn, project and stay alert.
In these images of the left hemisphere we see the activity of the groups of neurons that participate in the movement of the right index. In the first image thousands of seconds before the finger moves, the neurons of the cortezamotora are activated (pink) while sending instructions to the muscles of the finger.
In this image, 40 thousands of seconds after the order of movement is sent, neurons in the sensory cortex "turn on". This occurs when the neurons receive signals from the extension receptors of the muscles of the finger, signals that indicate that the muscles contract and that the index moves.
