Endocrine System Notes PDF

Chapter 18 The Endocrine System 1 General Functions of Hormones ◼ Help regulate: ◼ extracellular fluid ◼ metabolism ◼ contraction of cardiac & smooth muscle ◼ glan...

Chapter 18 The Endocrine System 1 General Functions of Hormones ◼ Help regulate: ◼ extracellular fluid ◼ metabolism ◼ contraction of cardiac & smooth muscle ◼ glandular secretion ◼ some immune functions ◼ Growth & development ◼ Reproduction 2  Endocrine Glands Defined ◼ Exocrine glands ◼ secrete products into ducts which empty into body cavities or body surface ◼ sweat, oil, mucous, & digestive glands ◼ Endocrine glands ◼ secrete products (hormones) into bloodstream ◼ pituitary, thyroid, parathyroid, adrenal, pineal ◼ other organs secrete hormones as a 2nd function ◼ hypothalamus, thymus, pancreas,ovaries,testes, kidneys, stomach, liver, small intestine, skin, heart & placenta 3 Circulating & Local Hormones ◼ Circulating hormones ◼ act on distant targets ◼ travel in blood ◼ Local hormones ◼ paracrines act on neighboring cells ◼ autocrines act on same cell that secreted them 4 Action of Lipid-Soluble Hormones ◼ Hormone diffuses through phospholipid bilayer & into cell ◼ Binds to receptor turning on/off specific genes ◼ New mRNA is formed & directs synthesis of new proteins ◼ New protein alters cell’s activity 5 Action of Water-Soluble Hormones ◼ Can not diffuse through plasma membrane ◼ Hormone receptors are integral membrane proteins ◼ act as first messenger ◼ Receptor protein activates G-protein in membrane ◼ G-protein activates adenylate cyclase to convert ATP to cAMP in the cytosol 6  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 (oxytocin) 7  Types of anterior pituitary cells 1- Somatotrophs : - secrets human growth hormone (hGH), hGH in turn stimulate other tissues to secrete insulinlike growth factors which stimulate general body growth and metabolism. 2- Thyrotrophs: - secrete thyroid stimulating hormone (TSH), TSH regulate thyroid gland secrtion. 3- Gonadotrophs: - secrete two hormones follicle stimulating hormone (FSH) and luteinizing hormone (LH). These two hormones in turn stimulate secretion of estrogen and progesterone and maturation of oocytes in overies. They also stimulate the secretion of testosterone and sperm production in the testes. 8  Types of anterior pituitary cells 4- Lactotophs: - secrete prolactin which initiate milk production from mammary gland. 5- Corticotrophs: - secrete adrenocorticotropic hormone (ACTH), which stimulates the adrenal cortex to secrete glucocorticoids 9 Regulation of hGH 10  Regulating Thyroid Stimulating Hormone (TSH) Negative feedback system 11 Actions of Thyroid Hormones ◼ T3 & T4 = thyroid hormones responsible for our metabolic rate, synthesis of protein, breakdown of fats, use of glucose for ATP production ◼ Calcitonin = responsible for building of bone & stops reabsorption of bone (lower blood levels of Calcium) 12 Parathyroid Hormone ◼ Raise blood calcium levels ◼ increase activity of osteoclasts ◼ increases reabsorption of Ca+2 by kidney ◼ promote formation of calcitriol (vitamin D3) by kidney which increases absorption of Ca+2 and Mg+2 by intestinal tract ◼ Opposite function of calcitonin 13 Regulation of Calcium Blood Levels 14  Prolactin (PRL) ◼ Hypothalamus regulates lactotroph cells by secretion of PIH or PRH ◼ Lactotrophs produce prolactin ◼ Under right conditions, prolactin causes milk production ◼ Suckling reduces levels of hypothalamic inhibition and prolactin levels rise along with milk production 15 Adrenocorticotrophic Hormone ◼ Hypothalamus releasing hormones stimulate corticotrophs ◼ Corticotrophs secrete ACTH ◼ ACTH stimulates cells of the adrenal cortex that produce Mineralocorticoids 16  Mineralocorticoids ◼ Secreted from the cortex ◼ The major mineralocorticoid is aldosterone ◼ Functions ◼ increase reabsorption of Na+ with Cl- , bicarbonate and water following it ◼ promotes excretion of K+ and H+ 17 Regulation of Aldosterone 18  Adrenal Medulla ◼ Chromaffin cells receive direct innervation from sympathetic nervous system ◼ Produce epinephrine & norepinephrine ◼ Hormones are sympathomimetic ◼ effects mimic those of sympathetic NS ◼ cause fight-flight behavior 19 Posterior Pituitary Gland (Neurohypophysis) ◼ Does not synthesize hormones, it only sore and release hormone. ◼ Consists of axon terminals of hypothalamic neurons ◼ Neurons release two neurotransmitters that enter capillaries ◼ antidiuretic hormone(ADH) 20 ◼ oxytocin  Oxytocin ◼ Two target tissues (Uterus and mammary gland) affected by oxytocin ◼ During delivery ◼ baby’s head stretches cervix ◼ hormone release enhances uterine muscle contraction ◼ baby & placenta are delivered ◼ After delivery ◼ suckling & hearing baby’s cry stimulates milk ejection ◼ hormone causes muscle contraction & milk ejection 21 Regulation of ADH 22  Anatomy of Pancreas ◼ Cells (99%) in acini produce digestive enzymes ◼ Endocrine cells (1%) in pancreatic islets produce hormones 23 Cell Types in the Pancreatic Islets ◼ Alpha cells (20%) produce glucagon ◼ Beta cells (70%) produce insulin ◼ Delta cells (5%) produce somatostatin ◼ F cells produce pancreatic polypeptide 24 Regulation of Glucagon & Insulin Secretion 25