This, of course, the most important organ of the nervous system. It is covered with a hard shell (mening) and floats inside the skull in the so-called cerebrospinal fluid. Although the human brain weighs less than two kilograms on average, it is an exceptionally complex organ.
The brain contains many billions of neurons. Due to the complex interweaving of axons, each neuron is connected to several thousand others. The complexity of these interweaving is so great that sometimes it goes beyond our understanding. Despite this, studies of the most complex organ in the human body are conducted and bear fruit. A fruitful approach to the study of the brain is to examine it in parts and find out the specific functions of each of them.
The main parts of the brain are the hindbrain, midbrain and forebrain. Figure 3-5 shows their location relative to each other. If we go upwards from the spinal cord, then the hind brain will be the first on our way.

Posterior brain

The main components of the hindbrain are the medulla, the pons, and the cerebellum. The medulla is located at the junction of the brain with the spinal cord and is essentially a continuation of the spinal cord. It regulates such extremely important functions of the body as breathing, heartbeat, blood pressure, digestion, swallowing and vomiting. Disruption of the medulla oblongata is very dangerous, and taking drugs that are inactive on the medulla, a person questions his life. When the content of toxic substances in the medulla oblongata rises dramatically, the emetic center is activated to cleanse the body. Therefore, when very drunk people often feel sick. Further in the back brain the bridge is located. It provides training for the transmission of impulses through the spinal cord, and is also partly responsible for sleep and wakefulness.A special path of impulses (not shown in Figure 3-5), known as the reticular formation, passes through the medulla oblongata and the bridge. It is very important for alertness and wakefulness. Obviously, substances that cause sleep (barbiturates and tranquilizers) act on this part of the brain.
The third major part of the hindbrain is the cerebellum. It has a very complex structure, consists of several billion neurons. Its main task is to regulate the movement of body parts. The mechanism of action of the cerebellum is practically incomprehensible to us, it is only known that it coordinates the most diverse gestures, speech and maintains balance. Drugs that cause inconsistency in movements and loss of balance (for example, alcohol) affect the cerebellum.

The midbrain

It consists of two small formations: the internal mounds and external mounds. Internal hillocks are parts of the hearing system, they localize the sound source in space. Outer mounds do the same with visual stimuli. Localization of objects and sending messages about them are the main functions of these parts of the brain. Recognition and interpretation of visual and auditory stimuli occur somewhere in another part of the brain.