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Transcript
Lecture No 1. Endocrinology (Introduction) Prepared of prof.L.Bobyreva • Endocrinology is a science, which comprises the study the development, the structure and the functions of endocrine glands, biosynthesis, the mechanism of action and hormones metabolism in the organism, secretion of these hormones in norm and during dysfunction of endocrine glands, and the diseases of endocrine system. • The glands of internal secretion produce hormones and release them into the blood. These hormones have definite influence on the metabolism changing the function of the whole organism or separate organs and systems. Thus, the major object of endocrine system is the functioning coordination of organs and systems. It is realized in close interaction with the central nervous system. Therefore it is more correct to say about a neuroendocrine regulation and neuroendocrine system of the human organism. epiphysis hypophysis thyroid gland thymus Parathyroid glands thyroid gland adrenal cortex adrenal gland adrenal medulla pancreas Langergans islet ovaries testicles ovaries Parathy-roid glands The endocrine system is composed of: hypophysis (pituitary gland), thyroid gland, parathyroid glands, insular apparatus of pancreas, adrenal medulla and adrenal cortex, testicles, ovaries, epiphysis, and thymus. • Functional activity of endocrine system depends • • • on: ability of endocrine glands to produce the necessary amount of hormones; a state of target tissues. Target tissue is a tissue, which is sensitive to the action of definite hormone and having specific biological effect on this action. The ability of target tissues to react to the corresponding hormone is determined by the presence of receptors, which interact with this hormone. The endocrine function of an organism is provided with systems, which include: • endocrine glands secreting hormones; • hormones and different ways of their transport; • proper organs and target tissues, responding to action of hormones. At present there are following variants of hormones' action: • hormonal, i.e. the action on long distance from the place of forming; • isocrinal (local) action, when the chemical agent synthesized in one cell, to have an effect on the cell which is located in close contact with the first one. Releasing of this agent occurs into intertissue liquid or blood; • neurocrinal (neuroendocrinal) action, when hormone during releasing from nerve endings functions as neurotransmitter or neuromodulator , i.e. hormone acts as a substance which changes (usually intensifying) the action of neurotransmitter; • paracrinal action is the type of the isocrinal action but hormone forming in one cell enters into intertissue liquid and has an influence on some cells, located near it; • autocrinal action, when hormone releasing from the cell has definite influence on the same cell, changing its functional activity . Depending on the chemical composition, hormones are divided into: • albuminous (protein) hormones are adrenocorticotropic hormone (ACTH), somatotrophic hormone, melano-stimulating hormone (MSH), prolactin, parathyroid hormone, calcitonin, insulin, glucagon, thyrotropic hormone (thyroid-stimulating hormone) (TSH), follicle-stimulating hormone, luteinizing (interstitial cell-stimulating) hormone (ICSH), and tyroglobulin; • steriod (or lipidic) hormones are corticosterone, cortisol, aldosterone, progesterone, estradiol, estrone, estriol, testosterone; • amino acid derived hormones are adrenalin, noradrenaline (norepinephrine), thyroid hormones (triiodothyronine, tetraiodthyroxin). Hormones realize their biological action combining with receptors. Receptors are informational molecules, which transform the hormonal signal into hormonal activity. At present there are approximately 60 hormonal receptors. More than half of them are localized on the cell membranes. These are receptors to peptide hormones. Steroid hormones and amino acid derived hormones interact with receptors located intercellular (cytoplasmic and nuclear). R Influence to membrane (transport) Inactive protein kinase H cAMP АC H Active protein kinase R АМP Synthesis of proteine Resulting biological effect Activation of enzymes Membrane Mechanism of protein hormone action by force of cAMP activation: R- receptor, H – hormone, AC - adenylate cyclase. Са+protein H H Active calmodulin Inactive calmodulin R Ca2+ Activation Kinase phosphorylase s Ca2+ RР Resulting biological effect Membrane Mechanism of protein hormone action by force of Са2+. R – receptor; H – hormone. Ca2+ Biological effect of hormones interacting with receptors, localized on a plasmatic membrane, realizes with the collaboration of "secondary messenger": cyclic adenosine monophosphate (adenosine phosphoric acid) (AMP) – adrenocorticotropic hormone (ACTH), thyroidstimulating hormone (thyrothropin, TSH), folliclestimulating hormone (FSH), luteinizing hormone, melano-stimulating hormone (MSH), vasopressin (antidiuretic hormone), parathyroid hormone, adrenalin and others; ionized calcium (Ca++) – oxytocin, noradrenaline (norepinephrine) and others; "secondary messenger" is unknown – somatotrophic hormone, prolactin (lactotropin), insulin and others .