The hypothalamus owes its name to the fact that it is located at the base of the brain in the sub-tubercle region. Translated from the Latin hypothalamus, there is a hypothalamus. This is one of the oldest subcortical formations of the brain, most developed in higher mammals and humans.
The hypothalamus is an accumulation of nerve cells and projection pathways that connect it with other structures of the brain and spinal cord. More than three dozen paired nuclei of the hypothalamus are topographically divided into anterior, middle, and posterior groups, and its projection paths are divided into incoming and outgoing. Extensive anatomical and functional connections of the hypothalamus provide a wide range of its activity.
Two types of nuclei are concentrated in it. Some of them consist of neurosecretory cells producing hormones vasopressin and oxytocin. They are transported to the posterior pituitary gland and stored in it, as in a reservoir, and then released into the blood as needed. For example, in acute blood loss, emotional stress, fever and some other conditions, the secretion of vasopressin increases, which helps to increase blood pressure.
Vasopressin also regulates the formation of urine. And if for some reason the hypothalamus does not produce this hormone enough, a disease known as diabetes insipidus develops; while the body secretes urine in an excessively large amount.
Oxytocin stimulates the separation of milk by the lactating mammary gland and the contraction of the muscles of the uterus.
In other nuclei of the hypothalamus, peptide (protein) substances are synthesized that regulate the formation of the so-called tropic hormones in the cells of the anterior pituitary gland. These hormones (among them growth hormone, luteinizing, thyrotropic, adrenocorticotropic), in turn, excite the activity of many endocrine glands, including the thyroid, adrenal glands, and sex glands.
Thus, the pituitary gland located at the base of the brain (in the so-called Turkish saddle), connected through the pedicle to the hypothalamus, is both a repository of hormones coming here from the hypothalamus and a factory of hormones secreted by it under the stimulating effect of the hypothalamus.
The main functional role of the hypothalamic-pituitary system is the regulation of the vegetative functions of the body. In the nuclei of the hypothalamus, the finest coordination of the autonomic nervous system, which controls all internal organs, regulates metabolic processes in the body. This function of the hypothalamus is especially pronounced in conditions of any extreme, so-called stressful, effects on the body, including injuries, strong emotions, low and high ambient temperatures, and infections.
Of course, various departments of the central nervous system take part in the formation of reactions of the body to resist stressful effects, but the hypothalamus has a special role. The regulation of autonomic functions is carried out by him in these cases through the pituitary gland. Under the influence of the hypothalamus, an adrenocorticotropic hormone (ACTH) is secreted in the anterior pituitary gland, and it, in turn, stimulates the secretion of hormones of the adrenal cortex, which have an adaptive value in a stressful situation.
The hypothalamus ensures the constancy of the internal environment of the body. For example, in the event of a sharp change in air temperature, adaptation mechanisms come into play aimed at maintaining a constant body temperature, and they are “triggered” mainly by the hypothalamus with special heat-sensitive devices. At high ambient temperatures, peripheral vessels expand, sweating increases, and metabolism decreases At low temperatures, the peripheral vessels, on the contrary, narrow, the heart rate quickens, muscle tremors appear, and metabolism increases at.
The hypothalamus takes an active part in the regulation of the exchange of proteins, carbohydrates, salts and water in the body, in the activity of many organs and systems, in the formation of positive and negative emotions; it has centers that influence sexual behavior.
Feeling of hunger, appetite, satiety are also “subject to” the hypothalamus. It has centers of satiation and hunger. These are clusters of nerve cells that are sensitive to changes in the chemical composition of blood. When a person is hungry, the so-called hungry blood, in which there is little glucose, amino acids and fatty acids, acts on the nerve cells of the center of hunger, and they activate the higher structures of the brain, up to the anterior sections of the cerebral cortex. As a result, a person feels hunger. Subsequent satisfaction of this need (motivation and the formation of actions aimed at satisfying hunger) occurs with the direct participation of the higher parts of the central nervous system.