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ENDOCRINELECTf2008out - How do cells communicate How How...

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Unformatted text preview: How do cells communicate? How How are organ systems regulated? • cell-cell communication – gap junctions, etc…. • paracrine communication – paracrine factors (cytokines)-produced locally by cells • Examples: thromboxanes, histamine, tissue factors • synaptic communication – chemicals that bind to receptors onto another cell • travel short distances • _________________________________ – chemicals that are released and act at sites far away • receptors determine cellular response • ____________________ glands – release substances into blood that bind to cell receptors • amino acid derivative ‘hormones’ – norepinephrine, epinephrine, histamine • peptide hormones – atrial natriuretic peptide (ANP) – erythropoietin (EPO) – angiotensin II • glycoprotein hormones • these 3 classes of hormones act at the cell surface: – bind to plasma membrane receptors • “_________________________” receptors – ‘G protein’-coupled receptors » activate cellular responses » production of “second messenger” molecules ‘G-protein’ coupled receptors (Fig. 16-3) 1) 2) 3) inactive G protein bound to receptor ligand binds to receptor activates G-protein, causing G-protein to activate activates cellular enzymes to produce second messenger molecules molecules 4) type of G-protein complex that associates with the receptor determines the cellular,response to hormone etermines seconddmessengers: cAMP, IP DAG, and Ca Types of G-protein coupled hormone receptors: Types 1) receptor that activates adenylate cyclase receptor – results in cAMP production – causes phosphorylation of cellular proteins/channels » Example: _____ adrenergic receptors 1) inhibits adenylate cyclase; activates inhibits phosphodiesterases phosphodiesterases – reduces cAMP level – enzyme/channel inhibition through removal of enzyme/channel phosphate phosphate » Example: ______ adrenergic receptors Types of G-protein coupled hormone receptors: Types 1) activating phospholipase C – – – causes release of Ca++ from intracellular stores intracellular opening of Ca++ channels activates enzymes Example: ______ adrenergic receptors Martini, Fig. 16-3 British Journal of Anesthesia 93 (1): 34-52 (2004) Adrenergic receptor signalling pathways Note relationship between receptors and second messengers • other types of hormones (Fig. 16-4a): – steroid hormones (lipid derivatives) • diffuse through cell membrane • bind to intracellular receptor – cytoplasmic or nuclear location • causes changes in gene expression • Examples: – ________________: increase expression of ________________: Na+/K+ pumps Na – calcitriol: increase expression of calcium absorption mechanisms – thyroid hormone (T , T ; Fig. 16-4b) • Bind to carrier protein in plasma • Enters cell, binds to receptors inside cell – Mitochondria » _____________ energy metabolism – Nucleus » Change gene expression Fig. 16-4, Endocrine control Endocrine hypothalamic control of endocrine function 1) secretion of pituitary regulatory hormones • • releasing hormones or factors inhibitory hormones or factors – affects pituitary control of many endocrine organs 2) sympathetic control over adrenal medulla • epinephrine, norepinephrine release 3) directly releasing hormones directly • antidiuretic hormone (ADH) Hypothalamic control of endocrine function Fig. 16-5, Martini ‘Endocrine reflex’ Simplest mode of regulation negative feedback loop to: control centers site of hormone synthesis site of hormone release Fig. 16-8a, Martini Pituitary gland Pituitary • ___Anterior pituitary ___Anterior pituitary – regulating production of the following “tropic” regulating hormones hormones • • • • thyroid stimulating hormone follicle stimulating hormone (cell in ovary or testie) luteinizing hormone adrenocorticotropic hormone • Prolactin o Prolactin 4 • growth hormoneo 4 • melanocyte stimulating hormone o melanocyte 4 (Hypothalmus) (thyroid stimulating hormone) Corticotropin releasing hormone (adrenocorticotropic hormone) (leutinizing hormone) gonadotropin releasing hormone (leutinizing hormone) (thyroxine, triiodothyroxine) (hydrocortisone) Pituitary gland Pituitary • Posterior pituitary Posterior pituitary – hypothalamic neurons release the following hormones • Antidiuretic hormone (ADH) – osmoreceptive cells release ADH » when osmolarity rises above 280 mOsm above – ADH, in high concentration, causes vasoconstriction » known also as ‘_vassopressin_’ • Oxytocin – Stimulates smooth muscle contraction – Women: uterine contractions, milk let-down response – Men: stimulates smooth muscle contraction in sperm Men: duct during ejaculation Endocrine disruptions Endocrine • diabetes _inspidius_ diabetes _inspidius_ – Lack/reduction of ADH production • hyperthyroidism – excessive quantities of thyroid hormone release – ‘_Graves_ Disease’ • • • high metabolic rate, blood pressure, and heart rate restless, excitable, mood swings low excess energy, fatigues easily • hypoaldosteronism – – – – lack of renin production excess water and Na+ loss low blood volume and pressure change in membrane potential Fig. 16-10a, Martini Martini Calcium homeostasis Calcium • _Calcitonin • released by parafollicular cells in thyroid – inhibits osteoclasts – stimulates calcium deposition in bone • osteoblast stimulation – released as blood calcium levels rise Figure 16-12a Figure 16-13 Calcium homeostasis • __Parathyrod hormone____ – released by parathyroid gland – increases Ca++ reabsorption in kidney and intestine intestine • stimulates calcitriol in tubule cells – stimulates degradation of bone matrix • Osteoclast stimulated – released as blood calcium levels fall Figure 16-13 Glucose homeostasis • Pancreas – a “mixed gland” • _exocrine_ function to produce digestive _exocrine_ enzymes, secreted into pancreatic duct enzymes, • __endocrine__ function to produce insulin __endocrine__ and glucagon, cells in Islets of Langerhans and Figure 16-15a – Insulin; made by beta cells (small Insulin; peptides and proteins) peptides • works to lower blood glucose works ↑ rate of glucose transport into cells rate ↑ rate of glucose utilization in ATP synthesis rate ↑ rate of glucose to glycogen rate ↑ amino acid uptake and protein synthesis amino ↑ triglyceride synthesis in adipocytes triglyceride Figure 16-16 – Glucagon; made by alpha cells • works to raise blood glucose levels ↑ rate of glycogen breakdown in liver, muscle rate ↑ rate of fats to fatty acids (adipocytes) rate ↑ rate of glucose synthesis in liver synthesis » “gluconeogenesis” Figure 16-16 STOP STOP STOP STOP STOP DUECES! Digestion and hormones DUECES! Stimulus for release Hormone/source Function gastrin/stomach ↑ HCl secretion and gastric motility motility CCK/duodenum CCK/duodenum (cholecystokinin) (cholecystokinin) contraction of gall bladder; contraction pancreatic enzyme release pancreatic Acidic environment in Acidic duodenum duodenum secretin/duodenum ↓ gastric movement & acid secretion secretion ↑ bicarbonate release from pancreas pancreas Fats and carbohydrates Fats in small intestine in gastric inhibitory gastric peptide (G.I.P)/duodenum (G.I.P)/duodenum ↓ motility in stomach; stimulates pancrease to secrete insulin PNS (acetylcholine) Amino acids Stomach distension Presence of fats or Presence amino acids in small intestine intestine Parietal cells Parietal intrinsic factor (vit B12 absorption) intrinsic HCl HCl Chief cells pepsinogen Secretion of acid by gastric parietal cells parietal • 3 phases of gastric activity – Cephalic – Gastric – Intestinal • 3 phases of gastric activity – Cephalic – Gastric – Intestinal • 3 phases of gastric activity – Cephalic – Gastric – Intestinal • Movement of Movement materials in gut materials – peristalsis ...
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