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Transcript
Endocrine System Unit 6 Endocrine System …coordinates and controls the activities of the body • Regulates: – extracellular fluid – metabolism – biological clock – contraction of cardiac & smooth muscle – glandular secretion – some immune functions • Controls growth & development • Regulates reproductive system Endocrine System vs. Nervous System Endocrine System • • • • • hormones far from site of release cells throughout body seconds - hours - days long duration Nervous System • • • • • neurotransmitters close to release site muscles, glands, neurons milliseconds brief duration Hormones and Glands Hormones: Chemical substances that are produced in one part of the body and transported by the blood to influence activities in another part of the body Endocrine vs. Exocrine Endocrine Exocrine • hormones into blood • pituitary, thyroid, parathyroid. adrenal, pineal • secondary function • hypothalamus, thymus, pancreas, testes, ovaries, kidneys, stomach, GI, skin, heart, & placenta • ducts • cavity/surface • sweat, oil, mucous, digestive glands Hormone Activity and Cellular Response • A given hormone affects only target cells • Hormone receptors develop as a cell differentiates • Different cells may respond in different ways to the same hormone • Some hormones are present much of the time, while others appear only sporadically • The amount of a circulating hormone is usually governed by negativefeedback control • Hormones are usually broken down rapidly • A hormone can increase the rate at which other substances enter or leave the target cell • A hormone can stimulate a target cell to synthesize enzymes, proteins, or other substances • A hormone can prompt the target cell’s machinery to activate or suppress existing cellular enzymes Hormone Chemistry 1. Steroid hormones – fat-soluble molecules (made from cholesterol) • Sex hormones groups: estrogens, androgens and progesterones. • Males and females make all three, just in different amounts. • Steroids pass into a cell's nucleus, bind to specific receptors and genes and trigger the cell to make proteins. • Steroid hormones must attach to transport proteins synthesized by liver • improve transport by making them water-soluble 2. Amino acid derivatives – water-soluble molecules derived from amino acids • Epinephrine, insulin, growth hormone. • These hormones are stored in endocrine cells until needed. • They act by binding to protein receptors on the outside surface of the cell. The binding alerts a second messenger molecule inside the cell that activates enzymes and other cellular proteins or influences gene expression. • Regulate such processes as metabolism, lactation, growth and reproduction. • Amino Acid hormones circulate in ‘free’ form in blood Steroid Hormone Action Amino Acid Hormone Action Hormonal Interactions • Permissive effect – a second hormone, strengthens the effects of the first ex. thyroid strengthens epinephrine’s effect upon lipolysis • Synergistic effect – two hormones acting together for greater effect ex. estrogen & LH are both needed for oocyte production • Antagonistic effects – two hormones with opposite effects ex. insulin promotes glycogen formation & glucagon stimulates glycogen breakdown Control of Hormone Secretion • Regulated by signals from nervous system, chemical changes in the blood or by other hormones • Negative feedback control (most common) • decrease/increase in blood level is reversed • Positive feedback control • the change produced by the hormone causes more hormone to be released • Disorders involve either hyposecretion or hypersecretion of a hormone Endocrine Gland Stimuli How are endocrine glands stimulated? 1. Hormonal - where a hormone stimulates the gland to release its hormone • tropic hormone - a hormone that stimulates a gland to release another hormone • -tropin a suffix often used on tropic hormones 2. Humoral - where the gland monitors the conditions it is going to control 3. Neural - where a nerve impulse stimulates the gland to release its hormone Hypothalamus & Pituitary Gland Hypothalamus Oxytocin Antidiuretic hormone (ADH) Releasing hormones Inhibiting hormones Anterior Pituitary Growth hormone (GH) Thyroid stimulating hormone (TSH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL) Adrenocorticotropin hormone (ACTH) Melanocyte-stimulating hormone (MSH) Anterior Pituitary Hormones Posterior pituitary Posterior pituitary Posterior Pituitary Hormones • • • • • • ADH Oxytocin during Labor Stimulation of uterus by baby Hormone release from posterior pituitary Uterine smooth muscle contracts until birth of baby Baby pushed into cervix, increase hormone release More muscle contraction occurs When baby is born, positive feedback ceases Thyroid Gland Actions of Thyroid Hormones Control of T3 & T 4 Secretion Parathyroid Gland Regulation of Calcium Blood Levels Actions of Parathyroid Hormones Adrenal Gland Adrenal Gland Cortex Medulla • • receive innervation from sympathetic nervous system mineralocorticoids • Aldosterone • increase reabsorption of Na+ with Cl- (and H2O) • promotes excretion of K+ and H+ • glucocorticoids • cortisol • corticosterone • cortisone • androgens • dehydroepiandrosterone (DHEA) • release epinephrine and norepinephrine in response to stress • Produces rapid, drastic effects involving several targets (fight or flight response). Regulation of Aldosterone Glucocorticoids Cortisol • 95% of glucocorticoid activity • protein catabolism • glucose formation • stimulate lipolysis • resistance to stress • anti-inflammatory effects • depression of immune responses Summary of Adrenal Gland Hormones Stress Response Pancreas Functions of Pancreas Exocrine function - Acini - cells clusters that produce digestive enzymes Endocrine function - Islets of Langerhans - clusters of hormone secreting cells Regulation of Glucagon & Insulin Secretion Pancreatic Islet Hormones Pineal Gland Other Hormones Pituitary Gland Disorders Pituitary dwarfism - hyposecretion of hGH Giantism - hypersecretion of hGH (childhood) Acromegaly - hypersecretion of hGH (adult) Thyroid Gland Disorders Congenital hypothyroidism - hyposecretion of thyroid hormone Myxedema - hypothyroidism during adult years Grave’s disease - hyperthyroidism - exophthalmos (edema behind eyes) Goiter - enlarged thyroid Thyroid Hormone Disorders Hyperthyroidism - excessive secretion high basal metabolism (Grave’s disease), high temperature, sweating, weight loss, irritability, high bp Hypothyroidism - deficiency (cretinism) weight gain, lethargy, intolerance to cold, simple goiter Adrenal Gland Disorders Cushing’s Syndrome - hypersecretion of cortisol Addison’s Disease - hyposecretion of glucocorticoids and aldosterone Diabetes Mellitus & Hyperinsulinism Type I - insulin-dependent diabetes mellitus (IDDM) Type II - non-insulin-dependent diabetes mellitus (NIDDM)