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Hormones and the Endocrine SystemTypes of Intercellular Signaling: Endocrine Paracrine Autocrine Synaptic Neuroendocrine Endocrine System = Hormone-secreting cells + TissuesEndocrine glands: ductless, secrete hormones directly into body fluidsHormones: chemical signals that cause a response in target cells (receptor proteins for specific hormones) Affects 1 tissue, a few, or most tissues in body Or affect other endocrine glands (tropic hormones)Regulation by Positive & Negative Feedback Pheromones - Chemical signal from 1 individual to another individualEg. ant trail; sex phermones Hormones - Chemical signal from endocrine gland through blood to target cellEg. peptide, steroid hormones Local Regulators - Chemical signal from one cell to an adjacent cellEg. cytokines, growth factors, nitric oxide (NO) Major Endocrine Glands: Hypothalamus, pineal gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries/testesOrgans containing endocrine cells: Thymus, heart, liver, stomach, kidneys, small intestine Types of HormonesPeptide• Water-soluble• Bind to receptors on plasma membrane & triggers signal transduction pathway• Affects protein activity already present in cell• Rapid response• Short-lived• Eg. oxytocin, insulin, epinephrine Steroid• Lipid-soluble• Enters cell & binds to intracellular receptors• Causes change in gene expression (protein synthesis)• Slower response• Longer life• Eg. androgens (testosterone), estrogen, progesterone, cortisol Epinephrine: one hormone à many effectsLiver cells break down glycogen and release glucoseBlood vessels to skeletal muscles dilateBlood vessels to intestines constrictMaster Glands: Hypothalamus à Pituitary Gland Hypothalamus:• Receives info from nerves and brain• Initiates endocrine signalsPituitary Gland: Posterior pituitary gland:• Oxytocin: contract uterine muscles, eject milk in nursing• Antidiuretic Hormone (ADH): promote H2O retention by kidneys Anterior pituitary gland:• Follicle-stimulating hormone (FSH): development of ovarian follicles (eggs); promote sperm production• Luteinizing hormone (LH): trigger ovulation; stimulate testosterone production in testes Negative feedback systems:Thyroid hormonesBlood Ca2+ levelsBlood glucose levelsPositive feedback system:Oxytocin (birthing process; release of milk/suckling) Insulin & Glucagon: Control blood glucose levelsà High blood glucose à Insulin released from pancreas à Body cells take up glucoseLiver stores glucose as glycogen à Blood glucose drops à Glucagon released from pancreas à Liver breaks down glycogen and releases glucose into blood à Diabetes Mellitus• Type I diabetes (10%):deficiency of insulin– Insulin-dependent– Autoimmune disorder à beta cells of pancreas destroyed• Type II diabetes (90%): failure of target cells to respond to insulin– Non-insulin dependent– Insulin produced à cells don’t respond (defect in insulin receptor or response pathway)– Risk factors: obesity, lack of exercise Thyroid GlandGraves’ Disease:• Autoimmune disorder• Antibodies bind to TSH receptor• Hyperthyroidism• High temp, sweating, weight loss, high BP Adrenal Gland: responsible for stress response Anabolic-Androgenic Steroid (AAS) Use• Legally prescribed to treat hormone deficiency, loss of muscle mass (cancer, AIDS)• Used to enhance performance and improve physical appearance Effects of AAS Abuse (Source: www.drugabuse.gov/infofacts/steroids.html)Aggression, extreme mood swings, liver damage, jaundice, fluid retention, high blood pressure, increases in LDL (“bad” cholesterol), decreases in HDL (“good” cholesterol), renal failure, severe can For men—shrinking of the testicles, reduced sperm count, infertility, baldness, development of breasts, increased risk for prostate cancerFor women—growth of facial hair, male-pattern baldness, changes in or cessation of the menstrual cycle, enlargement of the clitoris, deepened voiceFor adolescents—stunted growth due to premature skeletal maturation and accelerated puberty changes; risk of not reaching expected height if AAS is taken before the typical adolescent growth spurtIn addition, people who inject AAS run the added risk of contracting or transmitting HIV/AIDS or hepatitis
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