Exam 1 ReviewPPT 1:- Endocrinology: intercellular chemical communication- Endocrine system: main function is to maintain internal homeostasiso Support of cell growtho Coordination developmento Coordination reproductiono Facilitation of responses to external stimuli- Endocrine Communication Systemo Endocrine gland  hormone  blood  target cell  transduction  amplification  effector  response- 4 Classes of Hormoneso Peptideso Lipids Cholesterol metabolites  sterols, steroids Fatty acid metabolites  eicosanoids Retinoic acid metaboliteso Amino acid derivativeso Gases (nitric oxide)- Different types of secretionso Endocrine  secrete long distanceo Paracrine  secrete to target cells in close proximityo Autocrine  target cells of secretion are selfo Pheromonal  secretion by one organisms and sensation/response in a second organism- Hormones are potent  doesn’t take much for a responseo Mili  10^-3o Micro  10^-6o Nano  10^-9- Not all signaling molecules are in body at low concentrations, however- Endocrine organso- Classical Endocrine Glandso Thyroid gland Secretes thyroid hormone  regulates the body’s overall metabolismo Parathyroid gland there are 4 secretes parathyroid hormone absolute control over calcium levels in bodyo Adrenal gland there are 2, one above each kidney Secretes adrenaline, aldosterone, and cortisol  maintains salt levels in blood, maintains BP, help control kidney function, controloverall fluid concentrations in body, and control of glucose metabolism and the immune systemo Pancreas Secretes glucagon, somatostatin, and others control blood glucose and overall homeostasiso Gonads  ovary and testes, secretion of sex hormoneso Pituitary gland Secretes tropic hormones  thyroid stimulating hormone, follicle stimulating hormone, adrenocotropic hormone, and other Controls activity of many other endocrine glands (thyroid, ovaries, adrenal)- Exocrine glands  secrete products into ducts- Endocrine glands  secrete hormones into blood- How does a hormone find its receptor?o If it is large/charged, it probably cant enter cell and receptor will be on cell surfaceo Lipid soluble (steroid hormones) will have receptors likely on inside of cell in cytoplasm or nucleus Peptide hormones never use these receptors; they use membrane-bound receptors- Steroid hormone receptors are ligand-activated transcription factorso For steroid hormone to change cell function  change in transcription of genes must occur- How peptide hormones signalo Hormone binds to outer surface of receptor on cell surface and a signal passes through receptor to its cytoplasmic endo Signal is generated inside cello Some peptide hormones use GPCR to generate intracellular signals- Speed in which hormone acts is determined by structure of hormoneo Allosteric changes in receptor protein shapeo Signaling cascades are very rapido Opening/closing of ion channels also cause rapid responseso Intranuclear receptor transduction triggers changes in gene transcription  protein synthesis affected  takes longer time (minutes to days)- Cholesterolo Very insoluble in watero Can build up in arteries  arthrosclerosiso Cause gall stoneso Essential component of cell membraneso PRECURSOR OF ALL STEROID HORMONESo Cleavage if side chain is first step in synthesis of steroid hormones- Steroid hormoneso Adrenal steroids  21 carbonso Progestin  21 carbonso Androgens  19 carbonso Estrogen  18 carbonsPPT 2:- General features of Endocrine Systemo Endocrine glands are ductlesso Have rich supply of bloodo Hormones produced are secreted into bloodstreamo Hormones travel through blood to target cells both close by and far awayo Hormone receptors are specific binding sites on target cells- Endocrine vs exocrine glandso Endocrine are ductless, comprised of endocrine cells Means there are no ducts that lead to outside of body Since ductless, endocrine glands secrete hormones directly into bloodstreamo Exocrine have ducts Have ducts that lead to outside of body  example: sweat glands- Terminating Hormone Actionso Feedback inhibitiono Metabolism of hormoneo Switching off intracellular pathway which led to a response of target cell- Congenital hypothyroidismo Caused by mutation in the TSH geneo Makes people insensitive to thyroid stimulating hormone- Not all endocrine glands are regulated by pituitary axiso The following are not Hormones secreted by kidney and those involved in calcium homeostasis Atrium of heart involved in regulation of BP Hormones secreted by fat- Steroid hormoneso Produced by the gonads and adrenal cortexo Cannot be stored in vesicles in endocrine cells that produced them As soon as their produced, they diffuse into the bloodstreamo Lipid soluble and receptors are located inside their target cell- Peptide hormoneso Comprised of chains of amino acidso Synthesized on ribosomes of rough ERo Can be stored in vesicles until they are needed at a later pointo Do not readily pass through cell membrane; water soluble receptors found on cell surface of target cells- Hormone-Receptor Interactionso Protein that binds a ligand with high affinity and low capacity; binding must be saturable- Agonist vs. Antagonisto Agonist  molecules that bind the receptor and induce all the post-receptor events thatlead to a biological effect Act like “normal” hormone, but less potento Antagonist  molecule that bind the receptor and block binding of the agonist Prevents triggering of intracellular signaling events- Signal transductionso Can be accomplished one of two ways Either by a series of biochemical changes within the cell Modifying the membrane potential by movement of ions in/out of cello Biochemical changes can be initiated by either Directly via intrinsic enzymatic activities (kinases) within the receptor Activating intracellular messenger molecules- Receptors may be broadly classified into 4 groups that differ in their mode of action and in molecules that transmit their signalso GPCR’s  depend on GTP for their function; largest family of receptorso Receptor tyrosine kinases (RTKs)  membrane bound receptors; function by phosphorylating themselves and recruiting downstream signaling componentso Ion channels  proteins which open upon activation; respond to ligands or voltage changes across membraneo Nuclear receptors  bind cell-permeable molecules such