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Chapter 36 Signaling Molecules: 1) 2) Neurotransmitters Local signaling Molecules a) Secreted into extracellular fluid b) Short lived c) Very local effects 3) Pheromones a) Signal other individuals b) Sensed by vomeronasal organ 4) Hormones Hormones Produced by endocrine system – Endocrine glands/cells – Some neurons Delivered by blood then interstitial fluid Received by target cells – Cells with membrane receptors for that specific hormone – Lipid hormones diffuse through cell membrane (they are non-polar) Intracellular receptors Bind lipid Hormones like steroids Testosterone & thyroid hormones Often affect promoters regulating transcription Why do they need carrier proteins in blood? Intracellular Receptor Membrane Receptors Bind peptide/protein hormones Binding produces 2nd messenger mols. Like cAMP cAMP initiates chain reaction resulting series of chem. rxns is called a cascade Example: Glucagon Glucagon induced cascade Anterior Pituitary Hormones Regulated by Hypothalamus Hypothalamus monitors blood levels of thyroid hormones (T3/T4) and cortisol Low levels of T3/T4 or cortisol cause hypothalamus to signal Anterior Pituitary Neurons in hypothal. make releasing hormones (_RH) that signal the anterior pituitary to begin secreting hormones Releasing Hormones Produced by hypothalamus CRH = Corticotropin Releasing Hormone In response to low cortisol levels Coritsol helps maintain blood glucose levels High cortisol levels may result from stress TRH = Thyrotropin Releasing Hormone In response to low thyroid hormone level in blood Negative feedback loops Slow production of Releasing hormones by Hypothalamus High blood thyroid hormone levels = slow TRH production High blood cortisol levels in blood = slow CRH production Transmission of ___RH Releasing hormones produced in hypothalamus neruons flow into hypothalamus capillary bed Blood & hormones flow to 2nd capillary bed in anterior pituitary where TRH and CRH bind to receptors in anterior pituitary Anterior Pituitary Response RHs binding to receptors on Ant. Pituitary cells begin cascade of rxns leading to….. Release of TSH (thyroid stimulating hormone) or ACTH (adreno corticotropin) TSH also called thyrotropin -tropins stimulate other glands These hormones travel through blood to their target endocrine glands Thyroid Gland Response TSH binds to thyroid receptors Cascade of reactions results in release of T3 and T4 (thyroxins) High T3/T4 levels result in negative feedback to Hypothalamus and Anterior pituitary..stops TRH and TSH production T3/T4 regulate metabolism, growth & maturation Adrenal Gland Response ACTH binds to adrenal cortex receptors Cascade of reactions results in release of cortisol High cortisol levels in blood cause negative feedback to Hypothalamus and Anterior pituitary..stops CRH and ATCH production cortisol regulates blood glucose levels, stress response, excess = poor growth/imune system, cushings syndroms Other Ant. Pit. Hormones FSH – Follicle-stimulating Hormone Stimulates follicle to release egg (see ch 44) Stimulates sperm production in males LH – Luteininzing Hormone Stimulates gamete formation (see ch 44) Prolactin – causes lactation Growth Hormone- duhh Posterior Pituitary Function Hormones produced in cell bodies in the hypothalamus Axons of hypothamamic nerves extend into the posterior pituitary Action potentials trigger the release of hormones into capillaries Blood carries hormones to target organs Posterior Pituitary Hormones ADH – AntiDiuretic Hormone * Controls water excretion by kidney Oxytocin – controls…. * Uterine contractions/ lactation Pancreatic Hormones Hormones produced in Pancreatic Islets 3 types of cells in islets 1) alpha cells = glucagon 2) beta cells = insulin 3) Delta cells = somatostatin Glucagon = peptide hormone Low blood glucose triggers alpha cells Glucagon produced, binds to liver cells Cascade causes breakdown of glycogen into glucose High blood glucose levels = neg. feedback Insulin High blood glucose levels trigger beta cells Produce insulin Insulin cascade resulting in uptake of glucose – (only hormone to do this) Targets skeletal muscle, fat & liver cells Promotes: protein, fat & glycogen synthesis Low glucose levels = Neg. feedback Somatostatin Produced by Delta cells Regulated digestion Inhibits insulin glucagon Diabetes mellitus Cells do not take up glucose properly Type I = autoimmune attack on B cells (juvenile onset diabetes) Type II = target cells ignore insulin Beta cells constant production of insulin fail Insulin shots required Caused by genetics & obesity Symptoms of Diabetes Sugar accumulated in blood/ urine upsets water-solute balance kidney damage Cells burn protein/fats in absence of glucose Produces ketones ketoacidosis Affects brain, bloodvessels & nerves amputations