It is not a secret to anyone that our body and the systems it consists of are controlled by a number of things. Naturally, everyone thinks of our brain as a control organ, when it comes to sending order within our body, however, not everyone knows that there are also hormones that shape our entire life. There are two regulatory systems by which the body adjusts to changes in the environment, circumstances and our daily routine. The first one is our central nervous system, with our brain as a major organ in that system, quickly transmitting a signal (in pulses) via a network of nerves and nerve cells; the second one is our endocrine system, carrying out chemical regulation by hormones, which are spread inside the body through blood. Hormones affect organs, which are distant from the place of their allotment. Hormones are standard for all mammals, including humans (Mandal, 2009).
Before we can understand what effect the hormones have on us, we have to figure out where they come from. In the human body there are several endocrine glands that secrete specific chemical activators, hormones, which have a strong impact on our health by controlling and regulating a variety of processes. Hormones are secretions of endocrine glands and are released directly into the bloodstream and have high physiological activity. The main endocrine glands of mammals – the pituitary gland, parathyroid glands, adrenal cortex, adrenal medulla, islet tissue of the pancreas, gonads (testes and ovaries), placenta and hormone-producing areas of the gastrointestinal tract (Mandal, 2009). Hormones, as regulators, which work directly with the organs do not only contribute to our physical state, but mental health as well. In other words, such aspect as a women's ability to conceive a child, a women's ability to bear one, one's sexual attraction, beauty, functionality of various organs, and much more, all of these things depend upon the amount and the ratio of hormones that are produced and discharged into the blood. In total, what goes for hormones' work, there are several basic functions. As we have already discussed, the first is physical, mental and sexual development of a person. Another feature is the adaptation of the organism to certain conditions. For example, human reaction to stress, change in temperature, etc. Thirdly, upon hormones depends the constancy of the internal state of the organism, i.e. homeostasis. Finally, hormones are a kind of signal substances for the body, as they establish relationships between organs and tissues, indicating certain changes and processes (Davis, n. d.).
Movement of hormones
Hormones, once in the bloodstream, must be received by the relevant target-organs. Transport of macromolecular (protein) hormones is poorly understood due to the lack of accurate data on molecular weight and chemical structure of many of them. Hormones with relatively small molecular weight, such as thyroid and steroid, are rapidly bound to plasma proteins, so blood levels of hormones in a bound form is higher than in free; these two forms are in a dynamic equilibrium. Available hormones exhibit biological activity, and in some cases it was clearly shown that they are extracted from the blood to the target organs. The significance of protein binding of hormones in the blood is not clear.
Actions of hormones
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.
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 endocrine glands and hormones allowed to uncover 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 (Physiologic Effects of Thyroid Hormones, n. d.).
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 sensitive to the impact of hormones). 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.
In General, hormones act at specific target organs and cause significant physiological changes. The hormone can have several target organs, and when caused by physiological changes may affect a number of body functions. For example, maintaining normal levels of glucose in the blood - which is largely controlled by hormones – is important for the life of the whole organism. Hormones sometimes act jointly; thus, the effect of a hormone can depend on the presence of other hormones. Growth hormone, for example, is ineffective in the absence of thyroid hormone.
The action of hormones at the cellular level is carried out by two main mechanisms: enter the cells, usually water soluble, make an influence on the cell membrane, through the receptors, and easily pass through the membrane hormones (lipid soluble) – via receptors in the cell cytoplasm. In all cases, only the presence of a specific protein receptor determines the sensitivity of cells to this hormone, i.e. makes it a "target" (Mandal, 2009). The first mechanism of action is studied in detail on the example of adrenaline, is that the hormone binds to its specific receptors on the cell surface; the binding triggers a series of reactions resulting in the formation of the so-called second intermediaries that have a direct impact on cellular metabolism. And of cyclic amp and calcium ions are used for the transmission of the external signal inside cells in a variety of organisms at all levels of the evolutionary ladder. However, some membrane receptors, in particular receptors of insulin, there is a shorter way: they permeate through the membrane, and when a part of the molecule binds the hormone on the cell surface, the other part begins to function as an active enzyme on the side facing the inside of the cell; this provides a manifestation of hormonal effect. The second mechanism of action is via cytoplasmic receptors, it is characteristic for steroid hormones (hormones of the adrenal cortex and sex) and thyroid hormones. Infiltrating the cell containing the appropriate receptor, the hormone forms a hormone-receptor complex. This complex undergoes activation, and then enters the cell nucleus, where the hormone has a direct impact on the expression of specific genes, stimulating the synthesis of specific RNA and proteins. These newly formed proteins, usually short-lived, responsible for the changes that make the physiological effect of the hormone.
All in all, hormones and their contribution to our health are enormous and, therefore, it is crucial to keep our secretion organs in shape, as they have a vital effect on the well being of the whole organism.
Davis, Sandra I. "The Effects of Hormones on The Physiological System." The Effects of Hormones on The Physiological System. N.p., n.d. Web. 10 July 2015.
"Endocrine Glands and Types of Hormones." What Is the Function of Endocrine Glands & Types Of Hormones Released? Ed. Bradley Anawalt, Susan Kirk, and Dorothy Shulman. N.p., 2013. Web. 10 July 2015. <http://www.hormone.org/hormones-and-health/the-endocrine-system/endocrine-glands-and-types-of-hormones>.
Mandal, Ananya. "Physiology of Hormones." News-Medical.net. N.p., 25 Nov. 2009. Web. 10 July 2015. <http://www.news-medical.net/health/Physiology-of-Hormones.aspx>.
Mandal, Ananya. "What Are Hormones?" News-Medical. N.p., 25 Nov. 2009. Web. 10 July 2015.
"Physiologic Effects of Thyroid Hormones." Physiologic Effects of Thyroid Hormones. N.p., n.d. Web. 10 July 2015. <http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/thyroid/physio.html>.