Published on August 3, 2014

Author: tushar3891

Source: authorstream.com


ENDOCRINE SYSTEM & HORMONAL FEEDBACK MECHANISM : ENDOCRINE SYSTEM & HORMONAL FEEDBACK MECHANISM ANIRBAN KUMAR CLASS-XI-JCM-2 INTRODUCTION: INTRODUCTION CHEMICAL MESSENGERS ENDROCINE GLANDS INTRODUCTION: INTRODUCTION All the physiological activities are regulated by two major systems in the body Nervous system Endocrine system These two system interact with one another and regulate the body function. Endocrine system functions by secreting some chemical substances called chemical messengers or chemical mediators. CHEMICAL MESSENGERS: CHEMICAL MESSENGERS The chemical messengers are mainly secreted from endocrine. Glands. Some chemical messengers are also secreted by nerve ending and the cells various other tissues also. All the chemical messengers carry the message(signal) from the controlling cells(signaling cells) to the target cells. These messenger substances may be the hormones or hormone like substances. CHEMICAL MESSENGERS(Contd): CHEMICAL MESSENGERS(Contd) Generally the chemical messengers are classified into two types Classical hormones secreted by endocrine glands. Local hormones secreted from other tissues. Recent method of classification has four types messengers. Endocrine messengers Neurocrine messengers Paracrine messengers Autocrine messenger ENDOCRINE MESSENGERS: ENDOCRINE MESSENGERS Endocrine messengers are the classical hormones, which are secreted by the endocrine glands and transported by blood to the target organ or tissues (site of action). NEUROCRINE MESSENGERS: NEUROCRINE MESSENGERS Neurocrine messengers are also known as neurotransmitters, neuro-hormones or neural messengers. Neurotransmitters are released from the nerve ending These chemical mediators carry the message from the nerve ending to the target cells. Some neurotransmitters move to the distant target cell through the blood. The neurotransmitters released at the synapses also belongs to messengers. PARACRINE MESSENGERS: PARACRINE MESSENGERS The paracrine messengers are the chemical messengers, which diffuse from the control cells to the target cells through the interstitial fluid. Some of these substances directly enter the neighboring target cells through gap junctions Such substances are also called juxtacrine messengers AUTOCRINE MESSENGERS: AUTOCRINE MESSENGERS Autocrine messengers are the chemical messengers that control the source cells which secrete them. These are also called intracellular chemical mediators. Some of the chemical mediators can act as more than one type of chemical messengers eg . Noradrenalin and dopamine function as classical hormones as well as neuro transmitters. Similarly histamine acts as neurotransmitter and paracrine messengers. 2. ENDOCRINE GLANDS: 2. ENDOCRINE GLANDS The endocrine glands play an important role in homeostasis and controlling various other activities in the body by secreting the hormones The endocrine glands are also called ductless glands because the hormone directly released into the blood. The hormones are transported by blood to the target organs or tissues in different parts of the body, where the action are executed. Endocrine Glands,Hormones,Functions& Structure : Endocrine Glands,Hormones,Functions & Structure GLAND/TISSUE HORMONES MAJOR FUNCTIONS CHEMICAL STRUCTURE Hypothalamus Thyrotropin releasing hormone(TRH) Corticotropin -releasing hormone(CRH) Growth hormone- releasing hormone(GHRH) Growth hormone inhibitory hormone(GHIH) ( somatostatin ) Gonadotropin - releasing hormone( GnRH ) Dopamine or prolactin -inhibiting factor(PIF) Stimulates secretion of TSH and Prolactin Causes release of ACTH Causes release of GH Inhibits release of GH Causes release of LH and FSH Inhibits release of Prolactin Peptide Peptide Peptide Peptide Amine Contd.: Contd . GLAND/ TISSUE HORMONES MAJOR FUNCTIONS CHEMICAL STRUCTURE Anterior pituitary Growth hormone Thyroid –stimulating hormone(TSH) Adrenocorticotropic hormone (ACTH) Prolactin Follicle-stimulating hormone(FSH) Luteinizing hormone(LH) Stimulates protein synthesis and over all growth of most cell and tissues Stimulates synthesis & secretion of thyroid hormone ( thyroxine & triiodothyronine ) Stimulates synthesis & secretion of adrenocortical hormone ( cortisol,androgens,aldosterone .) Promotes development of female breasts and secretion of milk. Causes growth of follicle in the ovaries & sperm maturation in sertoli cells of testis. Stimulates testosterone synthesis in Leydig cell of testis,stimulates ovulation, formation of corpus luteum & estrogen and progesterone synthesis in ovaries. Peptide Peptide Peptide Peptide Peptide Peptide PowerPoint Presentation: GLAND/ TISSUE HORMONES MAJOR FUNCTIONS Chemicalstructure Posterior pituitary Antidiuretic hormone (ADH) (also called vasopressin) Oxytocin Increases water re absorption By the kidneys &causes vasoconstriction &increased blood pressure, Stimulates milk ejection from breasts & uterine contractation Peptide Peptide Thyroid Thyroxin (T4) & Triiodothyronin (T3) Calcitonin Increases the rate of chemical reaction in most of the cells thus increasing metabolic rate. Promotes deposition of calcium in the bones. Amine Peptide PowerPoint Presentation: Gland/Tissue Hormones Major Functions Chemical Structure Adrenal cortex Cortisol Aldosterone Has multiple metabolic functions for controlling metabolism of protiens , Carbohydrates and fats , also has anti-inflammatory effects. Increases renal sodium reabsorption,potassium secretion & hydrogen ion secretion. Steroids Steroids Adrenal medulla Norepinephrine , epinephrine Same effects as sympathetic stimulation Amine Parathyroid Parathyroid hormone (PTH) Controls serum calcium ion concentration by increasing calcium absorption by the gut and kidneys and releasing calcium from bones Peptide PowerPoint Presentation: Gland/Tissue Hormones Major Functions Chemical Structure Pancreas Insulin ( β cells) Glucagon ( α cells) Promotes glucose entry in many cells, and in this way controls carbohydrate metabolism. Increases synthesis & release of glucose from the liver into the body fluids. Peptide Peptide Testes Testosterone Promotes development of male reproductive system and male secondary sexual characteristics . Steroid Ovaries Estrogens Progesterone Promotes the growth development of female reproductive system and female secondary sexual characteristics. Stimulates secretion of uterine milk by the endometrial glands Steroid Steroid PowerPoint Presentation: G land/Tissue Hormones Major Functions Chemical Structure Placenta Human chorionic gonadotropin(HCG) Human somatomammotropin Estrogens Progesterone Promotes growth of corpus luteum and secretion of estrogens progestrogens by corpus luteum . Probably helps promote development of some fetal tissue as well as mammary gland -same- -same- Peptide Peptide Steroid Steroid Kidney Renin 1,25-Dihydroxycholecalcife-rol Erythropoietin Catalyses conversion of angiotensinogen to angiotensin I (acts as an enzyme) Increases intestinal absorption of calcium and bone mineralization Increases erythrocyte production Peptide Steroid Peptide PowerPoint Presentation: Gland/Tissue Hormones Major Functions Chemical Structure Heart Atrial natriuretic peptide (ANP) Increases sodium excretion by kidneys, reduces blood pressure . Peptide Stomach Gastrin Stimulates HCl secretion by parietal cells. Peptide Small intestine Secretin Cholecystokinin (CCK) Stimulates pancreatic acinar cells release bicarbonate and water. Stimulates gallbladder contraction and release of pancreatic enzymes Peptide Peptide Adipocytes Leptin Inhibits appetite, stimulates thermogenesis Peptide What is a feedback mechanism: What is a feedback mechanism Feedback is (generally) information about actions. PowerPoint Presentation: In cybernetics and control theory , feedback is a process whereby some proportion or in general, function, of the output signal of a system is passed (fed back) to the input. Often this is done intentionally, in order to control the dynamic behaviour of the system. Feedback is observed or used in various areas dealing with complex systems, such as engineering , architecture , economics , and biology . Drawing a feedback loop: Drawing a feedback loop Lines are usually drawn, directed from input through the system and to output. The feedback is shown by another arrowed line, directed from output outside the system to an input, resulting in a loop on the diagram, called feedback loop . This notion is important; for example, the feedback loop is a convenient place for a control device. In nature : In nature In biological systems such as organisms , ecosystems , or the biosphere , most parameters must stay under control within a narrow range around a certain optimal level under certain environmental conditions. The deviation of the optimal value of the controlled parameter can result from the changes in internal and external environments. A change of some of the environmental conditions may also require change of that range to change for the system to function. The value of the parameter to maintain is recorded by a reception system and conveyed to a regulation module via an information channel. Positive and negative feedback: Positive and negative feedback Biological systems contain many types of regulatory circuits, among which positive and negative feedbacks. Positive and negative don't imply consequences of the feedback have positive or negative final effect. The negative feedback loop tends to slow down a process, while the positive feedback loop tends to accelerate it. Useful vocab: Useful vocab negative feedback The stopping of the synthesis of an enzyme by the accumulation of the products of the enzyme-mediated reaction. negative feedback control   Occurs when information produced by the feedback reverses the direction of the response; regulates the secretion of most hormones . negative feedback loop A biochemical pathway where the products of the reaction inhibit production of the enzyme that controlled their formation. Negative feedback: Negative feedback Feedback and regulation are self related. The negative feedback helps to maintain stability in a system in spite of external changes. It is related to homeostasis . Positive feedback amplifies possibilities of divergences (evolution, change of goals); it is the condition to change, evolution, growth; it gives the system the ability to access new points of equilibrium An example of a simple negative feedback loop: An example of a simple negative feedback loop What if you get cold?: What if you get cold? What if your blood sugar changes?: What if your blood sugar changes? Integrating organs with feedback: Integrating organs with feedback PowerPoint Presentation: For example, in an organism, most positive feedbacks provide for fast autoexcitation of elements of endocrine and nervous systems (in particular, in stress responses conditions) and play a key role in regulation of morphogenesis, growth, and development of organs, all processes which are in essence a rapid escape from the initial state. Homeostasis is especially visible in the nervous and endocrine systems when considered at organism level. Endocrine system : Endocrine system The endocrine system is a control system of ductless glands that secrete chemical messengers called hormones that circulate within the body via the bloodstream to affect distant organs . Hormones act as "messengers", and are carried by the bloodstream to different cells in the body, which interpret these messages and act on them. The endocrine system does not include exocrine glands such as salivary glands , sweat glands and glands within the gastrointestinal tract . What is a hormone?: What is a hormone? hor·mone (hôr ' mōn') n. A substance, usually a peptide or steroid, produced by one tissue and conveyed by the bloodstream to another to effect physiological activity, such as growth or metabolism. How are hormones classified: How are hormones classified Hormones are grouped into three classes based on their structure: steroids peptides amines Steriods: Steriods Steroids are lipids derived from cholesterol. Testosterone is the male sex hormone . Estradiol, similar in structure to testosterone, is responsible for many female sex characteristics. Steroid hormones are secreted by the gonads , adrenal cortex, and placenta . Steroid structure: Steroid structure Peptides and Amines : Peptides and Amines Peptides are short chains of amino acids ; most hormones are peptides. They are secreted by the pituitary , parathyroid, heart , stomach , liver, and kidneys. Amines are derived from the amino acid tyrosine and are secreted from the thyroid and the adrenal medulla. Solubility of the various hormone classes varies. PowerPoint Presentation: The integration of body functions in humans and other higher organisms is carried out by the nervous system, the immune system, and the endocrine system. The endocrine system is composed of a number of tissues that secrete their products, called endocrine hormones , into the circulatory system; from there they are disseminated throughout the body, regulating the function of distant tissues and maintaining homeostasis. In a separate but related system, exocrine tissues secrete their products into ducts and then to the outside of the body or to the intestinal tract. Endocrine Hormones: Endocrine Hormones Classically, endocrine hormones are considered to be derived from amino acids, peptides, or sterols and to act at sites distant from their tissue of origin. However, the latter definition has begun to blur as it is found that some secreted substances act at a distance (classical endocrines), close to the cells that secrete them (paracrines), or directly on the cell that secreted them (autocrines). Insulin-like growth factor-I (IGF-I) , which behaves as an endocrine, paracrine, and autocrine, provides a prime example of this difficulty. What is the amount of hormones in the blood?: What is the amount of hormones in the blood? Hormones are normally present in the plasma and interstitial tissue at concentrations in the range of 10-7M to 10-10M. Because of these very low physiological concentrations, sensitive protein receptors have evolved in target tissues to sense the presence of very weak signals. In addition, systemic feedback mechanisms have evolved to regulate the production of endocrine hormones. PowerPoint Presentation: Once a hormone is secreted by an endocrine tissue, it generally binds to a specific plasma protein carrier, with the complex being disseminated to distant tissues. Plasma carrier proteins exist for all classes of endocrine hormones. Carrier proteins for peptide hormones prevent hormone destruction by plasma proteases. Carriers for steroid and thyroid hormones allow these very hydrophobic substances to be present in the plasma at concentrations several hundred-fold greater than their solubility in water would permit. Carriers for small, hydrophilic amino acid--derived hormones prevent their filtration through the renal glomerulus, greatly prolonging their circulating half-life. How do hormones travel in the blood! Nonsteroid hormones (water soluble) do not enter the cell but bind to plasma membrane receptors, generating a chemical signal (second messenger) inside the target cell. Five different second messenger chemicals, including cyclic AMP have been identified. Second messengers activate other intracellular chemicals to produce the target cell response.: Nonsteroid hormones (water soluble) do not enter the cell but bind to plasma membrane receptors, generating a chemical signal ( second messenger ) inside the target cell. Five different second messenger chemicals, including cyclic AMP have been identified. Second messengers activate other intracellular chemicals to produce the target cell response. Action of nonsteroid hormones: Action of nonsteroid hormones Step two: Step two Step Three: Step Three Action of steroid hormone: Action of steroid hormone The second mechanism involves steroid hormones, which pass through the plasma membrane and act in a two step process . PowerPoint Presentation: Steroid hormones bind, once inside the cell, to the nuclear membrane receptors, producing an activated hormone-receptor complex. PowerPoint Presentation: The activated hormone-receptor complex binds to DNA and activates specific genes, increasing production of proteins. PowerPoint Presentation: Tissues capable of responding to endocrines have 2 properties in common : they posses a receptor having very high affinity for hormone, and the receptor is coupled to a process that regulates metabolism of the target cells. Receptors for most amino acid--derived hormones and all peptide hormones are located on the plasma membrane. Activation of these receptors by hormones (the first messenger) leads to the intracellular production of a second messenger, such as cAMP, which is responsible for initiating the intracellular biological response. Steroid and thyroid hormones are hydrophobic and diffuse from their binding proteins in the plasma, across the plasma membrane to intracellularly localized receptors. The resultant complex of steroid and receptor bind to response elements of nuclear DNA, regulating the production of mRNA for specific proteins. How do tissue react to hormones? What we have seen so far..: What we have seen so far.. Stomach and intestines Gastrin Secretin Cholecystokinin (CCK) Somatostatin Neuropeptide Y Getting a head start on hormones: Getting a head start on hormones List of hormones and organs related to hormones: List of hormones and organs related to hormones Hypothalamus Thyrotropin-releasing hormone (TRH) Gonadotropin-releasing hormone (GnRH) Growth hormone-releasing hormone (GHRH) Corticotropin-releasing hormone (CRH) Somatostatin Dopamine Hypothalamus to Pituitary: Hypothalamus to Pituitary Pituitary gland: Pituitary gland Anterior lobe ( adenohypophysis ) GH ( human growth hormone ) PRL ( prolactin ) ACTH ( adrenocorticotropic hormone ) TSH ( thyroid-stimulating hormone ) FSH ( follicle-stimulating hormone ) LH ( luteinizing hormone ) Posterior lobe ( neurohypophysis ) Oxytocin ADH ( antidiuretic hormone ) Integration of blood and hormones: Integration of blood and hormones A division of labour: A division of labour PowerPoint Presentation: Pineal gland Melatonin Thyroid gland Thyroxine (T4), a form of thyroid hormone Triiodothyronine (T3), a form of thyroid hormone Calcitonin Parathyroid gland Parathyroid hormone (PTH) Heart Atrial-natriuretic peptide (ANP) PowerPoint Presentation: Adrenal glands Adrenal cortex Glucocorticoids - cortisol Mineralocorticoids - aldosterone Androgens (including testosterone ) Adrenal medulla Adrenaline ( epinephrine ) Noradrenaline ( norepinephrine ) Adrenal gland and kidney: Adrenal gland and kidney Kidney Renin Erythropoietin ( EPO ) Calcitriol PowerPoint Presentation: Liver Insulin-like growth factor Angiotensinogen Thrombopoietin http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/L/LiverHormones.html Islets of Langerhans in the pancreas Insulin Glucagon Somatostatin PowerPoint Presentation: Skin Calciferol ( vitamin D 3) Adipose tissue Leptin PowerPoint Presentation: In males only Testes Androgens ( testosterone ) PowerPoint Presentation: In females only Ovarian follicle Oestrogens Testosterone Corpus luteum Progesterone Placenta (when pregnant ) Progesterone Human chorionic gonadotrophin (HCG) Human placental lactogen (HPL) Your challenge….: Your challenge…. Most hormones turn on and off a response You should be able to make feed back loops for regulating levels of major chemical groups in the body. What are feedback loops for regulating: Oxygen and Carbon Dioxide Blood sugars ( you have seen it!) Blood salts Sexual and growth development More challenges…: More challenges… Can you link feedback mechanisms to specific systems? Could you make a comparative table pairing hormones with organ systems? What disorders are associated with your adrenal gland, thyroid gland, pancreas, bones and blood sugar imbalance. (see on-line references) A possible end..or beginning: A possible end..or beginning Feedback: Feedback This is my 1 st presentation, and I apologies for any mistake. So, please give your feedback at [email protected] THANK YOU: THANK YOU

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