Endocrine Physiology

KEY CONCEPTS OF ENDOCRINE ANATOMY AND PHYSIOLOGY A. Endocrine functioning 1. Hormones - regulate metabolic functions 2. Functions: • • • • •

Rates of biochemical reactions Transport substances - plasma membrane Growth and development Stress response Reproduction

3. Classification • • •

Tropic Releasing and inhibiting Peripheral

4. Characteristics • • • •

Respond to body/ environment rhythms Control rate of cellular activities Minute amounts 3 secretion Patterns • diurnal • pulsatile • depends on circulating substances

5. Control • •

Chemical - negative feedback, presence of other hormones Neural - cns

6. Hormonal receptors 7. Effects on the target cells • • •

direct effects permissive pharmacological

B. Specific Endocrine organs 1. Hypothalamus -hypophyseal system a. Anterior lobe (adenohypophysis) hormones: GH, TSH, ACTH, FSH, LH, ICSH, PRL b. Posterior lobe (neurohypophysis): stores and releases ADH and oxytocin 2. Thyroid: neck between 2 and 3 tracheal rings a. Hormones: T3 & T4 : regulate protein, fat, carbohydrate metabolism; regulate heat production, maintains growth and development

Thyrocalcitonin : lowers Calcium levels b. Functions of Thyroid hormones: • • • • • • •

glucose uptake by cells enhance fat metabolism basal metabolic rate (BMR) HR, COP, vasodilatation increase O2 consumption and CO2 beta-adrenergic receptors control secretion of other hormones

3. Parathyroid: Regulates serum calcium, magnesium, and phosphate 4. Pancreas a. Cells • •

Acinar cells (exocrine gland) Islet cells (endocrine gland)

• •

Alpha - secrete glucagon Beta - secrete insulin transport glucose to cells (reduce blood glucose) facilitates intracellular transport of K

•

Delta - secrete somatosatin

b. Role of Insulin: Regulated by chemicals, hormones, neural • • • • • •

Carbohydrate Metabolism: increase glucose transport, increase formation of glycogen, inhibits gluconeogenesis Fat Metabolism: increases triglyceride synthesis, fatty acid transport, fatty acid synthesis Protein Metabolism: Increases amino acid transport; Augments protein synthesis; Inhibits proteolysis stimulated by : blood glucose levels, amino acids, GI hormones, parasympathetic stimulation of beta cells Negative feedback - lowers insulin levels in response to high levels of insulin Decreases with low blood glucose levels, sympathetic stimulation of alpha cells, prostaglandins

5. Adrenal Glands a. Medulla : Catecholamines • • •

Epinephrine Norepinephrine Dopamine

b. Cortex: • • •

Androgen / estrogen Glucocorticoids (Cortisol) Mineralcorticoids (Aldosterone)

Key Points of GI Anatomy, Physiology

I. Four Major Activities of the GI Tract : • • • •

secretion of electrolytes, hormones, and enzymes to be used in breakdown of the ingested materials; movement of ingested products; digestion of food and fluids; absorption of end products into the bloodstream.

II. Gastrointestinal Secretions A. Mouth: alpha-amylase (ptyalin) B. Stomach: 1500 - 3000 ml of gastric juice per day. • • • •

Cardiac glands and Neck cells: mucus Peptic or chief cells: mucus and pepsinogen Parietal (oxyntic) cells: Intrinsic factor and hydrochloric acid G cells of pyloric antral region: gastrin

C. Small Intestine 1. Major Hormones • • • • •

Gastrin (duodenal mucosa) Secretin (duodenal and jejunal mucosa): Cholecystokinin (CCK) (duodenal and jujunal mucosa) Gastric inhibitory peptide (GIP) (duodenal and jejunal mucosa) Vasoactive intestinal peptide (VIP) (intrinsic plexuses, stomach -> colon)

2. Major Enzymes • • • • •

maltase: breaks maltose into glucose. lactase: breaks lactose into galactose and glucose. Sucrase: breaks sucrose into glucose and fructose Lipase (enzyme, found in 3 forms/locations: gastric mucosa, pancreas, and intestines): splits fats Peptidases (several enzymes of intestinal mucosa); splits proteins.

D. Pancreas - Secretions: 1500-2000 ml/day of pancreatic juice; pH = 8.3 (alkaline) 1. Major Enzymes: • • •

Lipase: works on fats [triglycerides to fatty acids & glycerol] Amylase: works on starches [amylose and amylopectic to maltose and dextrins] Trypsin: works on proteins [breaks amino acid bonds; activates other enzymatic precursors]

2. Major Hormones, islets of Langerhans • • •

Insulin (from Beta cells) Glucagon (from Alpha cells) Somatostatin (from Delta cells, islets of Langerhans)

E. Gallbladder, an accessory organ of digestion - concentrates and stores bile

F. Liver - over 400 functions; will review separately

Key Points of GI Assessment I. Anatomical Landmarks • • • • • • • • •

Right upper and lower quadrants; Left upper and lower quadrants; Subcostal margins Epigastric hollow; Umbilicus; Midline; Anteriosuperior spine (of iliac crest); Flanks; Costovertebral angle

II. Cardinal Symptoms of Gastrointestinal dysfunction: • • • • • • •

anorexia, nausea, vomiting, dysphagia, diarrhea, constipation, abdominal and referred pain.

III. Order of Assessment: 1. Inspect: • • •

Skin: scars, striae, dilated or engorged veins, spider angiomata; Umbilicus: eversion, caput medusae; Masses (movable or stationary)

2. Auscultate: • • • • • • • •

Position Supine; knees flexed or flat; Normal bowel sounds: 5-34/minute, random throughout abdomen. Intensity varies; loudest when meal overdue; Liver edges by "scratch": stethoscope over liver, lightly run fingernail outward; sound changes at borders Abnormal sounds: (a) Borborygmi: loud, rushing, high-pitched tinkling sounds heard proximal to intestinal obstruction until muscles become fatigued. (b) Absence: immobile bowel, due to peritonitis, paralytic ileus, advanced obstruction. (c) Bruit: like systolic murmur, turbulent flow through partially occluded artery. (d) Venous hum: over upper abdomen, liver: liver disease, portal or splenic vein thrombosis

3. Percuss: to establish distention, fluid, enlargement of solid organs (viscera); • •

Normal liver: dull; Normal spleen: dull;

• • •

Normal stomach: tympany when empty; Normal gut: hyperresonant to tympanic; "Test for shifting dullness" indicates free fluid in abdomen (ascites); Fluid wave maneuver: estimate large accumulation of ascitic fluid.

4. Palpation: • • • • •

to detect/elicit tenderness or muscle guarding, detect abdominal masses or fluids, to examine individual organs: rebound tenderness; involuntary rigidity or spasm.