Hormonal regulation of carbohydrate metabolism during muscular activity
The concept of hormones, their biological role.
ENDOCRINE SYSTEM – system of glands that produce hormones and secrete them directly into the blood. These glands, called endocrine glands or ductless, have no excretory ducts; they are located in different parts of the body, but functionally closely related. The figure shows the location of major endocrine glands in the human body. Absent the figure the pineal gland (epiphysis), studied enough, but now it belongs to the endocrine system. This gland is a small formation in the midbrain, and in mammals, it plays a role in neuroendocrine transducer, which goes from the eye through the brain nerve impulses turn into a hormonal signal, causing the secretion of the hormone melatonin. Melatonin affects biological rhythms, including daily fluctuations of physiological functions and seasonal reproductive cycles. In lower vertebrates, the pineal gland can directly perceive light (third eye).
HORMONES, organic compounds produced by certain cells and used to control the functions of the body, their regulation and coordination. In higher animals there are two regulatory systems by which the body adapts to constant internal and external changes. One of them is the nervous system, quickly transmitting a signal (in pulses) via a network of nerves and nerve cells; the other endocrine performing chemical regulation by hormones, which are transported by blood and affect distant from the place of their separation tissues and organs. Chemical communication system interacts with the nervous system; thus, some hormones function as mediators (mediators) between the nervous system and the authorities responsible for the effects. Thus, the distinction between the nervous and chemical coordination is not absolute.
Hormones are all mammals, including humans; they are found in other living organisms. The physiological action of hormones is aimed at:
1) providing humoral, i.e. carried through the blood, regulation of biological processes;
2) maintaining the integrity and constancy of the internal environment, harmonious interaction between cellular components of the body;
3) the regulation of the processes of growth, maturation and reproduction.
The pituitary gland is the main gland of internal secretion, the activity of which depends on the activity of other glands. The pituitary gland located in the skull under the brain, therefore is also called the lower brain appendage. And location, and the structure and origin of the pituitary gland dough is associated with the nervous system, which it has not effect, either enhancing or inhibiting its production of hormones.
Despite the small size and weight only about a gram. the pituitary gland is actually two glands in one body (anterior lobe is one gland, and the posterior and intermediate lobe is a second iron).
The pituitary gland consists of three lobes – anterior, consisting of cells of glandular tissue, rear, consisting of cells of nervous tissue, and intermediate, closely connected with the rear portion. Each of the lobes of the pituitary produces its own hormones.
Hormones regulate the activity of all cells of the body. They affect acuity and physical dexterity, vitality and growth to determine the growth of hair, tone of voice, libido, and behavior. Thanks to the endocrine system people can adapt to extreme temperature fluctuations, excess or lack of food, physical and emotional stress. The study of the physiological action of the endocrine glands revealed the secrets of sexual function and the miracle of birth and to answer the question, why are some people tall and others low, some full, others thin, some are slow, others fast, some strong, some weak.
In the normal state there is a harmonious balance between the activity of the endocrine glands, the nervous system and the response of target tissues (tissues that are sent to the impact). Any violation in each of these links leads quickly to deviations from the norm. Excessive or insufficient production of hormones is the cause of various diseases associated with deep chemical changes in the body.
What are hormones? According to classic definition, hormones are the secretions of endocrine glands and released directly into the bloodstream and having high physiological activity. The main endocrine glands of mammals – the pituitary, thyroid and parathyroid glands, adrenal cortex, adrenal medulla, islet tissue of the pancreas, gonads (testes and ovaries), placenta and hormone – producing areas of the gastrointestinal tract. In the body are synthesized and some compounds hormone-like actions. For example, studies of the hypothalamus showed that the number of secreted substances necessary for the release of pituitary hormones. These “releasing factors”, or liverini, were selected from different parts of the hypothalamus. They go to the pituitary gland through a system of blood vessels connecting the two structures. Because the hypothalamus in structure is not a gland, and releasing factors do, apparently, only in very close located the pituitary gland, those secreted by the hypothalamus substances can be considered hormones only when a broad understanding of the term.
Other issues even more difficult. The kidneys secrete into the bloodstream of the enzyme renin, which through activation of the angiotensin system (this system causes dilation of blood vessels) and stimulates the production of adrenal hormones, aldosterone. The regulation of the selection of aldosterone this system is very similar to how the hypothalamus stimulates the release of pituitary hormone ACTH (adrenocorticotropic hormone or corticotropin), regulating adrenal function. The kidneys also secrete erythropoietin – hormonal substance that stimulates the production of red blood cells. Is it possible to include kidney, endocrine organs? All these examples prove that the classical definition of hormones and endocrine glands is not inclusive enough.