Regulation of Physiological Process by Thyroid Hormones Essay

Regulation of Physiological Process by Thyroid Hormones - Essay Example On the other hand, each function may be controlled by several hormones, which act in concert. The secretion of the hormones in a normal human being is mainly based on negative feedback control, most of which involves the hypothalamic-pituitary axis that detects changes in the concentration of hormones secreted by peripheral endocrine glands. The hormones may also be secreted in response to changes in a controlled variable (Nussey & Whitehead 2001). The following examples illustrate as to how hormones regulate physiological function. The thyroid hormones, namely, thyroxine (T3) and tri-iodothyronine (T4) are secreted by the thyroid gland. They stimulate the oxygen consumption of most of the cells of the body, help in the regulation of lipid and carbohydrate metabolism, and are essential for normal growth and maturation. The thyroid hormones enter the cells after which T3 binds to the thyroid receptors in the nuclei. T4 binds, but not avidly. The thus formed hormone-receptor complex then binds to DNA via zinc fingers and affects the variety of different of different genes that code for enzymes which regulate cell function. The main physiological effect of thyroid hormones is calorigenic action (Ganong 2003). The hormones increase oxygen consumption of most of the tissues in the body except brain, testes, uterus, lymph nodes, spleen and anterior pituitary. The hormones also increase the metabolism of fatty acids. Due to increased calorigenic action, nitrogen excretion is increased and endogenous protein and fat st ores are metabolized, which may lead to weight loss. The hormones also cause hepatic conversion of carotene to vitamin A. Other functions include an increase in cardiac output by direct action on the heart and also by activating heat dissipation mechanisms. The pulse pressure and heart rate are also increased, thus shortening circulation time. In the central nervous system, the thyroid hormones increase the responsiveness of the brain tissue to catecholamines, thus activating the reticular activating system. The hormones also affect brain development and reflexes. They increase the rate of absorption of carbohydrate from the gastrointestinal tract.

Define what art is Essay Example | Topics and Well Written Essays - 500 words

Define what art is - Essay Example It is a weapon, a massive protest and a huge platform for revelation and revolution. Exploring the meaning of art as it appeals to a connoisseur is difficult but not always beyond comprehension. The essay attempts to identify, examine and explore few such intricate subtleties associated with the mighty term called â€Å"art†. In determining various approaches regarding the definition of art, first it is essential to judge the general view about the term. Generally, the term ‘art’ stands for a process or it can be denoted as a product which is intentionally arranged in an order with specific elements that will appeal and affect human senses or emotions. Art encompasses a diversified and a wide range of human activities pertaining to myriad creations and mode of expression. The canon of art includes many activities included in various spheres of artistry such as music, literature, film, sculpture and paintings among others. The definition of art has become considerably critical during the 20th century. Traditionally, art had been considered as a medium to make money or a device for amusement. Another traditional aspect of art is that the term exclusively refers to any â€Å"skill or mastery†. The concept of art transformed during the romantic period. During this period the perspective towards art completely changed and the term was viewed as â€Å"a special faculty of the human mind to be classified with religion and science† (The Gombrich Archive, â€Å"Press statement on The Story of Art†) The critical evaluation of art came into being during the Twentieth century. Scholar and artist, Richard Wollheim, envisaged three different approaches regarding the concept of art. Wollheim envisioned that art can be posited in three different paradigms namely ‘Realist Position’, ‘Objectivist Position’ and ‘Relativist Position’. These perspectives and distinguishing connotation undoubtedly helps in better understanding of the term.