Prepared by: Mr.Maulik chaudharyTHE ENDOCRINE SYSTEM * Two body systems are responsible for sending and receiving sensory information and coordinating body responses. These are the nervous system and the endocrine system. Together, they are sometimes referred to as the neuro-endocrine system. * The endocrine system regulates body activities by releasing hormones (chemical messengers) into the bloodstream, where they are carried throughout the entire body. * Hormonal responses may be almost instantaneous (Sudden), or may occur days later. There is a wide variety of hormonal effects.* The body contains two kinds of glands: — Exocrine glands secrete their products into body ducts, which carry the products into body cavities, the lumen of an organ, or the outer surface of the body. * Sudoriferous glands, sebaceous glands, mucous glands, and digestive glands. —Endocrine’ glands secrete’ their products (hormones) into the extracellular space around the secretory cells. The secretions diffuse into capillaries and are carried throughout the body by the circulatory system.* The endocrine system is composed of the body’s endocrine glands. These include: — The pituitary, — thyroid, — parathyroid, — adrenal — pineal glands — Pancreatic islets. * There are also many organs that have cells which secrete hormones, but are not exclusively endocrine organs. * These include: — The hypothalamus, thymus, pancreas, ovaries, testes, kidneys, stomach. liver, small intestine. skin, heart. and placenta.ENDOCRINE SYSTEM PINEAL cLano——_~faire ws HYPOTHALAMUS PITUITARY GLAND PARATHYROID GLANDS (behind thyroid gland) THYROID GLAND SKIN Trachea / THYMUS Lung GLAND ADRENAL (SUPRARENAL) HEART GLANDS STOMACH. KIDNEY Uterus uveR PANCREAS SMALL INTESTINE TESTES* Hormones are a chemical substances that are carried by a cell tissue and initiate specific action.HORMONES Hormones can have very powerful effects, even when present in very low concentrations. There are approximately 50 different hormones produced in the human body. The specific cells which are affected by a hormone are called target cells. Hormones influence their target cells by binding to proteins or glycoproteins in the cell membrane called receptors.. HORMONE FUNCTIONS Regulate the chemical composition and volume of the internal environment (extracellular fluid). Help regulate metabolism and energy balance. Help regulate contraction of smooth and cardiac muscle fibers and secretion by glands. Help maintain homeostasis, despite disruptions, such as infection, trauma, emotional stress, dehydration, starvation, hemorrhage, and temperature extremes.+ Regulate certain activities of the immune system. + Play a role in the smooth, sequential integration of growth and development. * Contribute to the basic processes of reproduction, including gamete production, fertilization, nourishment of the embryo and fetus, delivery, and nourishment of the newborn.What’s Hormone? * chemical messengers that are secreted directly into the blood, which carries them to organs and tissues of the body to exert their functions. Secretory vesicles * organic substances, produced in small amounts by specific tissues (endocrine glands), secreted into the blood stream to control the metabolic and biological Hormone activities in the target cells. molecules source- 2005 Pearson Education, Inc. Publishing Endocrine cellAnup Muni BajrechanaProperties of Hormones 1. Hormones are produced by a specialized glands and are secreted directly into the blood stream. 2. Hormones are transported by the blood stream from the endocrine cells to serve as ‘chemi-cal messenger’ which act on target cells or organs by regulating the rates of specific metabolic reactions. 3. Hormones exert their effects not where they are locally produced, but on other tissues of the body. 4. Hormones are required in very small amounts and their effect may be excitatory or inhibitory depending upon their concentration and the physiological state of the responding tissue. 5. Hormones belong to different types of chemical structure. They may be steroids, proteins, peptides or amino acid derivatives.Functions There are many types of hormones that act on different aspects of bodily functions and processes. Some of these include: Development and growth Metabolism of food items Sexual function and reproductive growth and health Cognitive (mental) function and mood Maintenance of body temperature and thirstClassification of hormones Hormones can be classified according to their Chemical nature, Mechanism of action, Nature of action, Stimulation of Endocrine glands and Effects of hormonesChemical nature of hormones Based on the chemical nature the hormones can be categorized into three groups Protein or peptide hormones e.g. insulin, glucagon, antidiuretic hormone, oxytocin. Steroid hormones e.g. glucocorticoids, mineralocorticoids, sex hormones. Amino acid derivatives e.g. epinephrine, norepinephrine, thyroxine (T4), triiodothyronine (T3). But more specifically it is divided into six classes, they are hormones steroid; amines; peptide; protein; glycoprotein and eicosanoid.Hormones. Steroid hormones Amine hormones Peptide hormones Protein hormones Glycoprotein hormones Eicosanoid hormones. Source Derived from cholesterol which belong to a chemical compounds known as steroids Hormones derived from the modification of amino, acids are referred to as amine hormones. Typically, the original structure of the amino acid is modified such that a —COOH, or carboxyl, group is removed, whereas the —NH?*, or amine group remains. Amine hormones are synthesized from the amino acids tryptophan or tyrosine. These hormones are made up of only few amino acid residues and they are usually present themselves in form of a linear chains These hormones are build up from large number of amino acid residues These are conjugated protein bound to carbohydrate which include galactose, mannose, fructose Made up of small fatty acid derivatives with a variety of arachidonic acid Example sex hormones, adrenal cortex hormones ‘An example of a hormone derived from tryptophan is melatonin, whil tyrosine derivatives include thyroid hormones and catecholamines Oxytocin and vasopressin Insulin, glucagon, somatotropins lute ing hormones follicle stimulating hormones, thyroid stimulating hormones ProstaglandinsMechanism of action of hormones U Group | Hormones Group II HormonesGroup | hormones Includes group of lipophilic hormones that are usually derived from cholesterol (except T; and T,). Steroid hormones are lipophilic (fat-loving) — meaning they can freely diffuse across the plasma membrane of a cell. bind to receptors in either the cytoplasm or nucleus of the target cell, to form an active receptor-hormone complex This activated complex will move into the nucleus and bind directly to DNA, acting as a transcription factor for gene expression. DNA E> mRNA EA protein mM) causes biochemical changes in the cell. Examples of steroid hormones include those produced by the gonads (i.e. estrogen, progesterone and testosterone)Group | hormones CYTOPLASM NUCLEUS steroid sé Line > | a _V Steroid on chromatin, activating hormone mRNA transcription | Oo ss? ® Complex binds to sites t Hormone-receptor complexUterine cell membrane Hormone (eg, oestrogen) a “+— Nucleus nt <+— Genome Receptor-hormone S mRNA complex } a Proteins Physi soot responses: (Tissue growth and differentiation)Group II hormones Include peptide hormones are hydrophylic and lipophobic (fat-hating) — meaning they cannot freely cross the plasma membrane They bind to receptors on the surface of the cell, which are typically coupled to internally anchored proteins (e.g. G proteins) The receptor complex activates a series of intracellular molecules called second messengers, which initiate cell activity This process is called signal transduction, because the external signal (hormone) is transduced via internal intermediaries Examples of second messengers include cyclic AMP (cAMP), calcium ions (Ca), nitric oxide (NO) and protein kinases The use of second messengers enables the amplification of the initial signal (as more molecules are activated) Peptide hormones include insulin, glucagon, leptin, ADH and oxytocin|Group II hormones CYTOPLASM SCRE (aC Number of molecules activatedi (e.g., FSH) SS Ovarian cell membrane (Generation of second messsnger) (Cyclic AMP or Ca”) Biochemical responses Physiological responses (e.g., ovarian growth)Nature of hormones action a. Local hormones— These hormones have a specific local effect through paracrine secretion, for example, hormone testosterone (a) Circulating hormones (@) Local hormones b. General hormones— These are hormones transported through circulation to the distal target tissue/organ examples are thyroid aenienan hormones and insulinStimulation of Endocrine glands a. Tropic hormones— --> ee": hormones that stimulate other : [vm : endocrine gland for secretion a: examples are TSH which stimulate T ee secretion of thyroid gland for the i sold oiene production of thyroid hormones = *""""""""" esos Target cells = poral b. Nontropic hormone— yi hormones that usually exert their effect ew on non-endocrine target tissues examples which increases the rate of oxygen @ consumption and metabolic activity of different cells in the body. of these hormone are Thyroid hormone OoTropic hormones Their primary function is to act at different endocrine glands than those from which are secreted, maintaining their integrity and regulating the secretion of other hormones. In the absence of these hormones their endocrine target tissues lose their structural integrity and stop secreting their hormones. Example: Thyroid-stimulating hormone (TSH) Non-tropic hormoi They do not regulate the secretion of other hormones. They directly stimulate target cells to induce effects. Example: Insulin, catecholamines.Tropic Hormones E.g. Gonadoliberin (affects anterior pituitary gland) and Somatostatin (affects anterior pituitary gland) ZNEffect of hormones a. Kinetic hormones— These hormones may cause muscle contraction, pigment migration, glandular secretion and others, example of these hormones is epinephrine b. Metabolic hormones— These are hormones that mainly caused changes in the rate of metabolism and balance the reaction examples include insulin, glucagon, parathyroid hormones. c. Morphogenetic hormones— These are hormones that mainly involved in growth and differentiation in the body, examples are Follicle stimulation hormones, luitenizing hormones and thyroid hormones