**5. Functions of the hypothalamus**

The hypothalamus is involved in different daily activities like eating or drinking, in the control of the body's temperature and energy maintenance, and in the process of memorizing and in stress control. It also modulates the endocrine system through its connections with the pituitary gland.

#### **5.1. Thermoregulation**

Thermoregulation is the process that allows maintenance of the body's temperature within normal ranges. In case of high body temperature, the hypothalamus responds through thermoregulatory heat loss behavior (either sweating or vasodilatation). If the body needs to be warm up, hypothalamus can determine heat production behavior (vasoconstriction, thermogenesis—heat production from muscles, brain or other organs, including the thyroid gland) [25].

They are of the hypothalamus responsible for controlling this process is the anterior one, more specific the preoptic nucleus.

#### **5.2. Regulation of food intake**

The hypothalamus controls appetite and food intake through the ventromedial, dorsomedial, paraventricular, and lateral hypothalamus nucleus. The ventromedial nucleus is referred to as the appetite-suppressing or anorexigenic center. Destruction of this nucleus leads to hyperpolyphagia, obesity, and to an aggressive behavior.

Contrary, the appetite-increasing or orexigenic center is considered to be the lateral hypothalamic nucleus that can lead to aphagia and cashexy in case of its destruction and to hyperphagia or polyphagia in case of its stimulation.

Appetite control is modulated by the leptin hormone released by the fatty cells that binds to specific hypothalamic receptors.

#### **5.3. Regulation of body water content**

Water control in the living organism is assured by the hypothalamus through the antidiuretic hormone (ADH) secretion. In cases of blood volume loss and dehydration, the ADH hormone is secreted from the supraoptic nucleus–that have osmoreceptor cells–and released in the circulation. The peptide is directed toward the specific receptor from kidneys and decreases the urine production with subsequent water retention in the organism.

#### **5.4. Center for autonomic nervous system**

The hypothalamus regulates both sympathetic and parasympathetic systems. The anterior region of the thalamus has an excitatory effect over the sympathetic system while the posterior and lateral ones have an excitatory effect over the parasympathetic system.

#### **5.5. Endocrine control**

Axons from the spinal cord can project in the hypothalamic region using the path of the spinohypothalamic tract. They carry out pain and temperature information. The hypothalamus exerts its effects within two projections: the spinothalamic tract reaching the lateral horn of the spinal cord of T1-L2 segments regulates the sympathetic autonomic response; the mammillotegmental tract and the dorsal longitudinal fasciculus carry out information from the posterior region of the hypothalamus while the anterior one connects with the thalamus

The hypothalamus is involved in different daily activities like eating or drinking, in the control of the body's temperature and energy maintenance, and in the process of memorizing and in stress control. It also modulates the endocrine system through its connections with the

Thermoregulation is the process that allows maintenance of the body's temperature within normal ranges. In case of high body temperature, the hypothalamus responds through thermoregulatory heat loss behavior (either sweating or vasodilatation). If the body needs to be warm up, hypothalamus can determine heat production behavior (vasoconstriction, thermogenesis—heat production from muscles, brain or other organs, including the thyroid

They are of the hypothalamus responsible for controlling this process is the anterior one,

The hypothalamus controls appetite and food intake through the ventromedial, dorsomedial, paraventricular, and lateral hypothalamus nucleus. The ventromedial nucleus is referred to as the appetite-suppressing or anorexigenic center. Destruction of this nucleus leads to hyper-

Contrary, the appetite-increasing or orexigenic center is considered to be the lateral hypothalamic nucleus that can lead to aphagia and cashexy in case of its destruction and to hyperpha-

Appetite control is modulated by the leptin hormone released by the fatty cells that binds to

Water control in the living organism is assured by the hypothalamus through the antidiuretic hormone (ADH) secretion. In cases of blood volume loss and dehydration, the ADH hormone

(mammillothalamic tract) and the above fornix.

**5. Functions of the hypothalamus**

pituitary gland.

gland) [25].

**5.1. Thermoregulation**

10 Hypothalamus in Health and Diseases

more specific the preoptic nucleus.

polyphagia, obesity, and to an aggressive behavior.

gia or polyphagia in case of its stimulation.

specific hypothalamic receptors.

**5.3. Regulation of body water content**

**5.2. Regulation of food intake**

The endocrine control is realized through the pituitary gland or the hypophysis situated below the tuberal region of the hypothalamus. The hypothalamus is connected with the posterior lobe of the gland through the hypothalamo-hypophyseal tract. Along these fibers, the AHD and oxytocin hormones are transported into the neurohypophysis where they are stocked in vesicles.

Hormones secretion in the body is regulated by the hypothalamus through the releasing and inhibitor factors: thyrotropin-releasing, gonadotropin-releasing, corticotrophin-releasing, somatostatin, and dopamine. These hormones are involved in the process of growth, in the reproduction, in the metabolism of the body, and also can assure the homeostasis of the body.

#### **5.6. Reproduction**

The reproduction function of an organism is assured by the hypothalamic-pituitary-gonadal axis. The gonadotropin-realizing hormone (GnRH) secreted by the hypothalamus stimulates the production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the anterior subdivision of the pituitary gland. Action of these two hormones on the gonads determines the estrogen and testosterone production.

Behavior in males and females is influenced as well by the sex steroids. The neurons in the preoptic are involved in the male sexual behavior while the ones from the tuberal regional exert their properties in females [26].

#### **5.7. The circadian rhythm**

The photosensible suprachiasmatic nucleus is involved, along with is connections with the pituitary gland, in the circadian rhythm. The suprachiasmatic nucleus receives electro-chemical information from the stimulated retina. The circadian rhythm represents the endogenous clock of an organism that is involved in the well-being of the body due to keeping within normal limits the major functions.

Despite its reduced size, the hypothalamus represents an important, integrative region of the brain with complex functions and multiple connections with essential cerebral structures.
