The hypothalamus owes its name to what is located at the base of the brain in the hypothalamus region. Translated from the Latin hypothalamus, there is a hypothalamus. This is one of the ancient subcortical formations of the brain, the most developed in higher mammals and humans.
A hypothalamus is a collection of nerve cells and projection paths connecting 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 – into the incoming and outgoing. Extensive anatomical and functional connections of the hypothalamus provide a wide range of its activity.
It contains two types of nuclei. Some of them consist of neurosecretory cells that produce the hormones vasopressin and oxytocin. They are transported to the posterior lobe of the pituitary gland and stored in it, as in a reservoir, and then excreted into the blood as needed. For example, in acute blood loss, emotional stress, fever, and some other conditions, vasopressin secretion increases, which contributes to high blood pressure.
Vasopressin also regulates urine formation. And if for any reason the hypothalamus does not produce enough of this hormone, a disease known as diabetes insipidus develops; at the same time, the body excretes urine in an excessively large amount.
Oxytocin stimulates the separation of milk with a lactating mammary gland and contraction of the muscles of the uterus.
In other nuclei of the hypothalamus, substances of a peptide (protein) nature are synthesized that regulate the formation of so-called tropic hormones in the cells of the anterior pituitary gland. These hormones (among them growth hormone, luteinizing, thyrotropic, adrenocorticotropic), in turn, stimulate the activity of many endocrine glands, including the thyroid, adrenal glands, sex glands.
Thus, the pituitary gland, which is connected with the hypothalamus through the pedicle, is located at the base of the brain (in the so-called Turkish saddle) and is a repository of hormones coming here from the hypothalamus and a factory of hormones secreted by it during the stimulating effect of the hypothalamus.
The main functional role of the hypothalamic-pituitary system is the regulation of the body’s autonomic functions. In the nuclei of the hypothalamus, the finest coordination of the activity of the autonomic nervous system takes place, which controls all the internal organs and regulates the metabolic processes in the body. This function of the hypothalamus is particularly pronounced in conditions of any extreme, so-called stressful effects on the body, including injuries, strong emotions, low and high temperature of the external environment, infections.
Of course, different departments of the central nervous system take part in shaping the reactions of the organism to stress, but the hypothalamus has a special role. The regulation of autonomic functions is carried out in these cases through the pituitary gland. Under the influence of the hypothalamus in the anterior lobe of the pituitary gland adrenocorticotropic hormone (ACTH) is released, and it, in turn, stimulates the secretion of adrenal cortex hormones that have an adaptive (adaptive) value in a stressful situation.
The hypothalamus ensures constancy of the internal environment of the body. For example, in the event of an abrupt change in air temperature, adaptation mechanisms are activated to maintain a constant body temperature, and they are “started” mainly by the hypothalamus with special temperature-sensitive devices. At high ambient temperatures, the peripheral vessels expand, sweating increases, and metabolism decreases in the body. At low temperatures, peripheral vessels, on the contrary, narrow, heart rhythm increases, muscle tremors appear, the exchange of substances increases at.
The hypothalamus takes an active part in the regulation of the metabolism 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 affect sexual behavior.
The feeling of hunger, appetite, saturation are also “subject to” the hypothalamus. It has centers of saturation and hunger. These are clusters of nerve cells that are sensitive to changes in the chemical composition of the blood. When a person is hungry, the so-called fasting blood, in which there is little glucose, amino acids and fatty acids, affects the nerve cells of the hunger center, and they activate the higher structures of the brain, up to the anterior parts of the cerebral cortex. As a result, a person feels hunger. The 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. And if the coordinated activity of the centers of hunger and satiety is disturbed under the influence of any pathological process, the patient’s appetite (hyperphagia) can be extremely intensified and, as a result, obesity develops.