Final.docx

Final – chapter 27: fluid, electrolyte, and acid-base homeostasis Fluid balance: fluid gained each day is equal to amount lost Electrolyte balance: neither a net gain nor loss of any ion Homeostasis: body “input” of water and electrolytes must be balanced by output How it works: excess gain requires...

Final – chapter 27: fluid, electrolyte, and acid-base homeostasis Fluid balance: fluid gained each day is equal to amount lost Electrolyte balance: neither a net gain nor loss of any ion Homeostasis: body “input” of water and electrolytes must be balanced by output How it works: excess gain requires selective elimination and excess loss requires prompt replacement (fluid volume remains relatively constant Imbalance: both totally volume/amount of compartment fluid is outside normal limit Total body water Most of our body weight is water, factors that effect this is age, fat content and gender as well as adipose and aging Stored: muscle mass (65%), fat (20%), less concentrated urine (Na+). As we get older and lose muscle mass and get more fat tissue we can’t hold onto water as well. Body fluid compartments ECF: provides constant environment + transports substances ICF: facilitates intracellular chemical reactions Relative volumes: intracellular volume is 25L overall, broken down into IF (12L), plasma (3L) Plasma and IF nearly identical (chemically), plasma contain more Na+ and few Cl than IF Differences between ECF IF Most abundant cation Sodium Potassium Most abundant anion Cl- HPO4 2- Concentration of protein anions 10 65 Sources of body water gain and loss: water enters via food and drink we intake also done by cellular respiration, defecation, and urination. Water exits the body by kidneys, lungs, skin, and intestine. Daily water loss: 2500mL (amount varies by route). Example, strenuous exercise and GI infection Regulating body water Big picture: fluid input must = fluid output or else imbalance occurs. Mechanisms rapid-acting & maintain to expense of IF Regulated water gain regulated water loss Renin Angiotensin II Osmoreceptors Aldosterone Dry mouth ANH ADH Regulating water gain: volume of metabolic water depends on aerobic respiration, controlled by thirst centers in hypothalamus. Dehydration: water loss > water gain. Fluid loss: decreased BP, causing renin released (makes angiotensin 1 to create #2 to stimulate thirst receptors), osmoreceptors triggered causing thirst to increase, increasing fluid intake. Dehydration Regulating water loss: sweating and exhalation, excess occurs by control (the amount and type of urine produced) volume Urinary salt loss= blood volume (urinary loss of ions regulated by hormones) Increased intake of NaCl Increased plasma concentration of Na and Cl Increased osmosis of water from intracellular fluid to interstitial fluid to plasma Increased blood volume 4a. Increased stretching of atria of heart, Increased release of atrial natriuretic peptide 4b. Decreased release of Renin by juxtaglomerular cells, Decreased formation of angiotensin II Increased glomerular filtration rate Reduced reabsorption of NaCl by kidneys Increased loss of water in urine by osmosis Decreased release of aldosterone Effects of ADH release stimulates thirst, insertion of water-channels and water permeability increases. Water intoxication Steady consumption of water causing water to enter cells and swelling. when the water is consumed too quickly to process water, because the osmolarity decreases and dilutes the solutes and creates an imbalance in the components and the water is going to move from the plasma in to ICF, to get rid of the extra water in the cell we are going to use an IV fluid (hypertonic solution) to add a lot of solutes into the plasma so water can be pulled out of the ICF and the cell Effects: Convulsions, coma, and possible death Regulation of water and electrolytes in ECF Inside the capillary: fluid in our plasma pushing on the capillary, blood hydrostatic pressure (BHP): fluid out of capillaries, into IF Blood colloid osmotic pressure (BCOP): fluid from IF, in capillaries Outside the capillary: interstitial fluid hydrostatic pressure (IFHP): fluid out of IF, into capillaries Interstitial fluid colloid osmotic pressure (IFCOP): fluid out of capillaries into IF Homeostatic fluid imbalances Edema: abnormally large amounts of fluid in intercellular tissue spaces (pressure, aldosterone, and proteins) Pitting edema: depression in swollen tissue Hypovolemia: abnormally low blood volume: decreased aldosterone and vigorous diuretic therapy. Regulation of water and electrolytes in ICF Plasma membrane: selectively permeable barrier (movement across membrane requires transport mechanisms Outside cell (ECF): more Na, more Cl Inside the cell (ICF): more K, more phosphate, more proteins Homeostasis: ECF and ICF similar osmolarity (solution are isotonic). Changes in ECF osmolarity – fluid imbalance (dehydration) Regulation of sodium Major contributor to osmolarity of ECF (Cl- also contributes) (changes affect compartment fluid volumes). Controlled by aldosterone, ADH, ANH Hyponatremia: sodium levels decreased (over hydration, ↑ ADH or ↓ aldosterone), water moves into the cell causing slower depolarization Hypernatremia: sodium levels increased (dehydrated, ↑ aldosterone, ↑ dietary intake, kidney disease). Water moves out of cell and cell crenates Regulation of potassium Major contributor to establishing resting membrane potential (essential for function of neurons, contraction of skeletal and cardiac muscle, controlled by hormones such as insulin and aldosterone) Hyperkalemia: K+ levels high in blood (↓ excretion, ↑ dietary intake, drugs, shift from ICF to ECF, RMP more positive) Hypokalemia: K+ levels low in blood (diuretics, vomiting/diarrhea, sweating, RMP more negative (reduced excitability of neurons and hyperexcitability od cardiac muscle) Acid-base balance Regulating H+ concentration in body fluids. Many molecules contain chemical groups that can either donate or accept H+ and behave as a weak acid or a weak base. Challenge is to maintain homeostasis, slight changes affect ion channels, membrane receptors, enzymatic activities. Review of the pH concept # of H+/1L solution (expressed as 0-14) H increases, pH down= acidic – more H than base ions H decreases, pH up= basic – more base than H pH of 7= neutral – H+ = base ions SLIDES 29-46 review!!!