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• The Endocrine System (the second messenger system of the body) I. Hormones: A.Endocrine system produces hormones (chemical messages) that are important in maintaining homeostasis & regulating reproduction, metobolic rate, growth & development plus it mobilizes the immune system. I. Hormones: B. A Hormone is a chemical messenger produced by a cell that causes specific changes in the cellular activity of other cells (target cells). Overview of the Endocrine System • The Role of Target Cell Receptors in Hormonal Action Figure 10-2 Overview of the Endocrine System • Classes of Hormone Receptor –Extracellular Receptors • Located in cell membrane • Targeted by –Amino acid derivatives –Peptides –Eicosanoids • Operates through a second messenger such as cyclic-AMP Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Membrane receptor First messengers (E, NE, peptide hormones, and eicosanoids) Hormonereceptor complex Cell membrane G protein G protein (inactive) (activated) Activates adenylate cyclase Acts as cAMP second messenger ATP Cytoplasm Nuclear envelope Activates kinase Nuclear pore Nucleus Alterations in enzyme activity; opens ion channels TARGET CELL RESPONSE DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 1 of 7 Membrane receptor G protein (inactive) Cell membrane Cytoplasm Nuclear envelope Nuclear pore Nucleus DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 2 of 7 Membrane receptor Hormonereceptor complex G protein (inactive) First messengers (E, NE, peptide hormones, and eicosanoids) Cell membrane Cytoplasm Nuclear envelope Nuclear pore Nucleus DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 3 of 7 Membrane receptor First messengers (E, NE, peptide hormones, and eicosanoids) Hormonereceptor complex Cell membrane G protein G protein (inactive) (activated) Activates adenylate cyclase Cytoplasm Nuclear envelope Nuclear pore Nucleus DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 4 of 7 Membrane receptor First messengers (E, NE, peptide hormones, and eicosanoids) Hormonereceptor complex Cell membrane G protein G protein (inactive) (activated) Activates adenylate cyclase Acts as cAMP second messenger ATP Cytoplasm Nuclear envelope Activates kinase Nuclear pore Nucleus DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 5 of 7 Membrane receptor First messengers (E, NE, peptide hormones, and eicosanoids) Hormonereceptor complex Cell membrane G protein G protein (inactive) (activated) Activates adenylate cyclase Acts as cAMP second messenger ATP Cytoplasm Nuclear envelope Activates kinase Nuclear pore Nucleus Alterations in enzyme activity; opens ion channels DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 6 of 7 Membrane receptor First messengers (E, NE, peptide hormones, and eicosanoids) Hormonereceptor complex Cell membrane G protein G protein (inactive) (activated) Activates adenylate cyclase Acts as cAMP second messenger ATP Cytoplasm Nuclear envelope Activates kinase Nuclear pore Nucleus Alterations in enzyme activity; opens ion channels TARGET CELL RESPONSE DNA Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 10-3(a) 7 of 7 C. Unlike exocrine glands that release their products at the body’s surface or into body cavities through ducts, the endocrine glands do not secrete substances into ducts instead their hormones are secreted directly into the surrounding extracellular space & then diffuse into nearby capillaries & are transported throughout the body in the blood. • D. The endocrine & nervous systems often work together to maintain homeostasis. • E. The nervous system uses neurotransmitters to act on cells (which is usually short-lived) to maintain homeostasis • F. The endocrine system uses hormones (whose effects last longer than neurons) to produce homeostasis. • G. Hormones are classified into 2 basic categories: peptides (including amino acids, polypeptides, & proteins) & steroids (complex rings of carbon & hydrogen atoms) synthesized by cholesterol. Ex. Gonadal hormones & adrenocortical hormones Now we are going to look at each gland individually: • These next few slides will be copied onto your paper but do not have blanks to fill in • H. Pituitary – found in sella turcia pea-size, gland. It is also called the Master Gland. The Anterior pituitary is hormone production glandular portion. Ex. GH (bone & muscle) & TSH (growth of thyroid) • The Posterior pituitary is the neural portion & extension of hypothalamus. Ex. Oxytocin (milk release) & ADH ( increase H O & BP) Hormones of the Anterior Pituitary • Pituitary Hormones and Their Targets The Pituitary Gland Figure 10-8 Hormones of the Posterior Pituitary • I. Thyroid-Found in anterior throat overlying inferior border of larynx. One of the largest endocrine glands & has a heavy blood supply. Ex. Thyroid hormone T3 & T4 contain iodine. • J. T3-T4 Function to 1) accelerate cellular metabolism, 2) tissue growth, 3) skeletal reproductive & nervous system development. Calcitonin lowers blood calcium levels. • K. Thyroid gland unique because it can store & slowly release its hormones (up to 3 months worth) Goiter= iodine or T3 / T4 deficiency L. Over active & under active thyroid can cause severe disturbances. Ex. Hypothroid syndrome – goiter or cretinism; Severe hyperthyroidism – Graves disease (autoimmune disorder that attacks the thyroid)-most common. M. Parathyroid – 4 to 8 embedded in posterior aspect of thyroid gland. Ex. PTH important in controlling level of calcium in blood. • N. Hyperparathyroidism- rare result of PTH deficiency untreated death may occur. Kidney stones, reflexes & skeletal muscle weakness. The Parathyroid Glands Figure 10-11 • O. Adrenal glands almond size atop the kidneys. 1. Adrenal Medulla (inner)epinephrine & norepinephrine 2. Adrenal cortex (outer)- Makes steroid hormones called Corticosteroids. Ex. Mineralcotricoids, Glucocorticoids, & Androgens Adrenal Medulla Produces two similar hormones 1. Epinephrine – aka Adrenaline; associated w/the fight or flight system. Axons stimulate hormone secretion. Increases heart rate and force, releases glucose, fatty acids into blood, opens airways Epinephrine Adrenal Medulla Produces two similar hormones 2. Norepinephrine: aka. Noradrenaline- associated w/the rest & digest system. Is the antagonist to epinephrine. These hormones prepare the body to deal with short-term stress Norepinephrine – Rest & Digest Adrenal Cortex-Mineralcorticoids (mainly aldosterone) Produced in outer adrenal cortex Regulate mineral content in blood, water, and electrolyte balance Target organ is the kidney Production stimulated by renin and aldosterone Adrenal Cortex: Glucocorticoids (including cortisone and cortisol) Promote normal cell metabolism Help resist long-term stressors Released in response to increased blood levels of ACTH Adrenal Cortex: Sex hormones Produced in the inner layer of the adrenal cortex Androgens (male hormones) and some estrogen (female hormones) Adrenal Gland Response to Stress • P. Pancreas- located partially behind the stomach. Mixed gland so has both endocrine & exocrine capabilities. • Islets of Langerhans-minute clusters of cells that produce pancreatic hormones. Ex. Insulinlowers blood sugar level & Glucagon –increases blood sugar P. Pancreas: –Islet cells secrete insulin and glucagon •Insulin produced by beta cells •Glucagon produced by alpha cells –Exocrine cells secrete enzymerich digestive fluid • Actions of Insulin and Glucagon –Insulin •Lowers blood glucose concentration •Increases glucose uptake, storage, and use by target cells •Targets liver, muscle, fat cells –Glucagon •Raises blood glucose concentration •Increases glycogen breakdown and glucose synthesis •Targets liver cells The Pancreas Figure 10-13(a) rd 3 Q. Pineal Gland: located in the ventricle of the brain secretes Melatonin associated w/sleep & wake cycles. R. Inhibits reproductive function S. Protects neural tissue from free radicals T. Its’ complete function is still unclear. Q. Pineal Gland: located in brain Thymus Gland Located posterior to the sternum Largest in infants and children Produces thymosin Matures some types of white blood cells Important in developing the immune system Reproductive Glands: Ovaries Estrogen Hormone: Produced by Graafian follicles or the placenta Stimulates the development of secondary female characteristics Matures female reproductive organs Helps prepare the uterus to receive a fertilized egg Helps maintain pregnancy Prepares the breasts to produce milk Reproductive Glands: Ovaries Progesterone Produced by the corpus luteum Acts with estrogen to bring about the menstrual cycle Helps in the implantation of an embryo in the uterus Reproductive Glands: Testes Interstitial cells of testes are hormoneproducing Produce several androgens (sex hormones) Reproductive Glands: Testes Testosterone (hormone) is the most important androgen Responsible for adult male secondary sex characteristics Promotes growth and maturation of male reproductive system Required for sperm cell production Other Hormone Producing Tissues & Organs: Parts of the small intestine Secretes hormones to control digestion Parts of the stomach –Kidneys Secretes three hormones • Calcitriol—Stimulates calcium and phosphate absorption in intestine • Erythropoietin (EPO)—Stimulates red blood cell production by bone marrow • Renin—Enzyme that leads to angiotensin II that triggers aldosterone from adrenal cortex Other Hormone Producing Tissues & Organs: Heart Specialized muscle cells secrete atrial natriuretic peptide (ANP) to lower blood volume or blood pressure • Adipose tissue (fat cells) – Secretes leptin to control appetite – Secretes resistin to reduce insulin response Many other areas have scattered endocrine cells Endocrine Functions of the Placenta Produces hormones that maintain the pregnancy Some hormones play a part in the delivery of the baby Produces HCG in addition to estrogen, progesterone, and other hormones Patterns of Hormonal Interaction • Kinds of Interaction between Hormones –Antagonistic (opposing effect) • E.g., calcitonin versus PTH –Synergistic (additive effect) • E.g., hGH and cortisol on glucose sparing –Permissive effect • E.g., epinephrine and thyroid hormones –Integrative effect • E.g., calcitriol and PTH on calcium levels Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Hormonal Interaction • Hormones Needed for Normal Growth –Growth Hormone –Thyroid Hormones –Insulin –Parathyroid Hormone –Calcitriol –Reproductive Hormones Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Patterns of Hormonal Interaction • Hormones and Stress • Stress—Any condition that threatens homeostasis • General Adaptation Syndrome to stress –Alarm phase (sympathetic ANS response) –Resistance phase (glucocorticoid response) –Exhaustion phase (organ system failure) Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Development of the Endocrine System Most endocrine organs operate smoothly until old age Menopause is brought about by lack of efficiency of the ovaries Problems associated with reduced estrogen are common Growth hormone production declines with age Many endocrine glands decrease output with age • The information on the next slides will be found on your notes papers II. Hormone Action • C. Hormones activate target cells by 1 of 2 methods, depending upon the chemical nature of the hormone: • 1) peptide hormones {water soluble} that bind to a receptor protein on the plasma membrane of the cell. The receptor protein, then stimulates the production of a second messenger (either cAMP or calcium.) II. Hormone Action • 2) steroid hormones {lipid soluble} that diffuse through the plasma membrane of the target cell & bind to receptor protein present in the cytoplasm that activates a DNA segment that turns on specific genes III. Control of Hormone Production • A. Endocrine glands release hormones in response to 1 or more of the following stimuli: • 1. Hormones form other endocrine glands • 2. Chemical characteristics of the blood • 3. Neural stimulation III. Control of Hormone Production • 4. most hormone production is regulated by negative feedback system. • a. negative feedback: hormones secretion is triggered by some internal or external stimulus, then rising hormones levels inhibit further hormone release resulting in blood levels of many hormones varying only within a very narrow margin. IV. Communication b/w the Hypothalamus & Pituitary Glands • A. Communication b/w the hypothalamus & the Anterior Pituitary Gland occurs through chemicals that are produced by the hypothalamus & delivered to the ant. pituitary through blood vessels. IV. Communication b/w the Hypothalamus & Pituitary Glands • B. Communication b/w the hypothalamus & the Posterior Pituitary Gland occurs through neurosecretory cells that connect the 2 glands. V. Antagonistic Hormones • A. When the body hormone levels drop below normal homeostasis levels the antagonistic hormones are secreted to bring the body back to homeostasis. • B. Ex. Bundles of cells in the pancreas called the islets of Langerhans contain 2 kinds of cells alpha (secrete glucagons) & beta (secrete insulin) cells, that control blood glucose concentrations by producing the antagonistic hormones insulin & glucagon VI. Major Endocrine Organs Gland Hormone Released Target Tissue/Organ Chief Function of Hormone Pineal Melatonin Various Tissues Involved in daily rhythms; possibly involved in maturation of sex organs Hypothalamus Hypothalamic-releasing & release-inhibiting hormones Anterior pituitary Regulate anterior pituitary hormones Anterior Pituitary Growth hormone (GH) Soft tissues, bones Mammary glnds Ovary, testes Gonads Adrenal cortex Thyroid Skin & Melanocytes Stimulates protein synth. & bone growth Prolactin; (LTH) Luteininzing Hormone; Follicle stimulating hormone (FSH); Adrenocorticotropic hormone (ACTH) Thyroid stimulating (TSH) MSH (Melanocyte stimulating Hormone) Stimulates milk production & secretion Reg. Oogenesis & spermatogenesis Same as LH Stimulate secretion of gluco-corticoids Stimulate secretion of T &T VI. Major Endocrine Organs Gland Hormone Released Target Tissue/Organ Chief Function of Hormone Posterior Pituitary Oxytocin Uterus,mammary glands Uterine contractions, release of milk Increases water retention & BP Increases metabolic rate; helps to result. growth & development Lowers blood calcium levels Increases rate of cellular metabolism Raises blood calcium levels Thyroid Antidiuretic Hormone (ADH); Thyroxin (T4) Calcitonin Triiodothyronine (T3) Kidneys, sweat glands All tissues Bones, kidneys, intestine Bone Parathyroid Parathyroid hormone (PTH) Bones, kidneys, intestine Thymus Thymosins T lymphocytes Stimulates maturation of T lymphocytes VI. Major Endocrine Organs Gland Hormone Released Target Tissue/ Organ Chief Function of Hormone Adrenal Medulla Epinephrine & Norepinephrine Cardiac & other muscles Stimulate “fight-orfight” reaction; raise blood glucose lvl. Adrenal Cortex Glucocorticoids ex. Cortisol Mineralcorticoids ex. Aldosterone Androgens ex. DHEA All tissues Kidneys Sex organs, skin, muscles Pancreas Insulin Glucagon Liver, muscles, adipose tissues Liver Raises blood glucose level Increase reabsorption of Na+ & to excrete K+ Stimulate onset of puberty, female sex drive Lowers blood glucose levels Increases blood glucose levels Adrenal Glands VI. Major Endocrine Organs Gland Hormone Released Target Tissue/ Organ Chief Function of Hormone Ovaries Estrogen Progesterone Relaxin Inhibin Uterus Uterus Pelvis, cervix pituitary Testes Testosterone Inhibin Testes Pituitary Regulates menstrual cycle, secondary sex characteristics. Reg.menstrual cycle, pregnancy Dilates cervix & birth canal Inhibits FSH release Regult. spermatogenesis, secondary sex characteristics inhibits FSH release Gonads • THE END!!!!