Bio 202 Anatomy & Physiology II - Fluid Balance (PDF)

Water, ARIZONA STATE UNIVERSITY College of Integrative Sciences & Arts Electrolyte, & Acid-Base Balance Bio 202 A natomy & Phy...

Water, ARIZONA STATE UNIVERSITY College of Integrative Sciences & Arts Electrolyte, & Acid-Base Balance Bio 202 A natomy & Physiology II Tonya A. Penkrot, Ph.D.  26.1 Body Fluid Compartments Body Water Content  Infants are 73% or more water (low body fat, low bone mass)  Adult males: ~60% water  Adult females: ~50% water (higher fat content, less skeletal muscle mass) Adipose tissue is least hydrated tissue of all Total body water in adults averages ~40 L  Water content declines to ~45% in old age © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.1 The major fluid compartments of the body. Total body water Volume = 40 L 60% of body weight Volume = 3 L, 20% of ECF Plasma Intracellular fluid (ICF) Interstitial fluid (IF) Volume = 25 L Volume = 12 L 40% of body weight 80% of ECF Extracellular fluid (ECF) Volume = 15 L 20% of body weight © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Composition of Body Fluids (cont.) Electrolytes ― Dissociate into ions in water  Examples: inorganic salts, all acids and bases, some proteins ― Ions conduct electrical current ― Greater osmotic power than nonelectrolytes  Greater ability to cause fluid shifts due to ability to dissociate into two or more ions  NaCl Na+ + Cl− (electrolyte; 2 particles)  MgCl2 Mg2+ + 2Cl− (electrolyte; 3 particles)  glucose glucose (nonelectrolyte; 1 particle) © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.2 Electrolyte composition 160 of blood plasma, interstitial fluid, and intracellular fluid. 140 120 Total solute concentration (mEq/L) Blood plasma Interstitial fluid 100 Intracellular fluid Na+ Sodium 80 K+ Potassium Ca2+ Calcium Mg2+ Magnesium 60  HCO3 Bicarbonate CI Chloride HPO4 2  Hydrogen 40 phosphate SO4 2  Sulfate 20 0   Na+ K+ Ca2+ Mg2+ HCO3 CI HPO42 SO42 Protein © 2016 Pea rs on Education, Inc. anions Bio 202 A&P ASU DPC T. Penkrot  Figure 26.3 Exchange of gases, nutrients, water, and wastes between the three fluid compartments of the body. Lungs Gastrointestinal Kidneys tract Blood O2 CO2 Nutrients H2O, H2O, Nitrogenous plasma Ions Ions wastes O2 CO2 Nutrients H2O Ions Nitrogenous Interstitial wastes fluid Intracellular fluid in tissue cells © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  26.2 Water Balance and ECF Osmolality  Water intake must equal water output: ~2500 ml/day  Water intake: most water is taken in via ingested foods and beverages, but small amount from metabolism Metabolic water (water of oxidation): water produced by cellular metabolism  Water output: urine (60%), insensible water loss (lost through skin and lungs), perspiration, and feces © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot 26.2 Water Balance and ECF Osmolality  Osmolality is maintained around 280–300 mOsm  Rise in osmolality Stimulates thirst Causes ADH release  Decrease in osmolality Causes thirst inhibition Causes ADH inhibition © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.4 Major sources of water intake and output. 100 ml Feces 4% Metabolism 10% 250 ml Sweat 8% 200 ml Insensible loss Foods 30% via skin and 750 ml 700 ml lungs 28% 2500 ml 1500 ml Urine 60% Beverages 60% 1500 ml Average intake Average output per day per day © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Water Intake  Thirst mechanism is driving force for water intake  Governed by hypothalamic thirst center Hypothalamic osmoreceptors detect ECF osmolality and are activated by: ― Increased plasma osmolality of 1–2% ― Dry mouth ― Decreased blood volume or pressure ― Angiotensin II or baroreceptor input © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.5 The thirst mechanism for regulating water intake. ECF osmolality Plasma volume (5–10%) Blood pressure Osmoreceptors Saliva Granular cells in hypothalamus in kidney Renin-angiotensin- aldoster one Dry mouth mechanism Angiotensin II Hypothalamic thirst center Sensation of thirst; person takes a drink Water moistens mouth, throat; stretches stomach, intestine Water absorbed from GI tract Initial stimulus Physiological response ECF osmolality Result Plasma volume Increases, stimulates © 2016 Pea rs on Education, Inc. Reduces, inhibits Bio 202 A&P ASU DPC T. Penkrot  Figure 26.6 Mechanisms and consequences of ADH release. ECF osmolality Na+ concentration in plasma Plasma volume Stimulates (5–10%), BP Osmoreceptors Inhibits in hypothalamus Negative feedback inhibits Baroreceptors in atria and Stimulates large vessels Stimulates Posterior pituitary Releases ADH Antidiuretic hormone (ADH) Targets Collecting ducts of kidneys Effects Water reabsorption Results in ECF osmolality Scant urine Plasma volume © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Disorders of Water Balance  Three principal abnormalities of water balance 1. Dehydration ― ECF water loss due to hemorrhage, severe burns, prolonged vomiting or diarrhea, profuse sweating, water deprivation, diuretic abuse, endocrine disturbances ― Signs and symptoms: “cottony” oral mucosa, thirst,dry flushed skin, oliguria ― May lead to weight loss, fever, mental confusion, hypovolemic shock, and loss of electrolytes © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Slide 1 Figure 26.7a Disturbances in water balance. 1 Excessive 2 ECF osmotic 3 Cells lose loss of H2O pressure rises H2O to ECF from ECF by osmosis; cells shrink Consequences of dehydration. If more water than solutes is lost, cells shrink. © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Disorders of Water Balance (cont.) 2. Hypotonic hydration ― Cellular overhydration, or water intoxication ― Occurs with renal insufficiency or rapid excess water ingestion ― ECF osmolality decreases, causing hyponatremia  Results in net osmosis of water into tissue cells and swelling of cells  Symptoms: severe metabolic disturbances, nausea, vomiting, muscular cramping, cerebral edema, and possible death Treated with hypertonic saline © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Slide 1 Figure 26.7b Disturbances in water balance. 1 Excessive 2 ECF osmotic 3 H2O moves into H2O enters pressure falls cells by osmosis; the ECF cells swell Consequences of hypotonic hydration (water gain). If more water than solutes is gained, cells swell. © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Disorders of Water Balance (cont.) 3. Edema ― Atypical accumulation of IF, resulting in tissue swelling (not cell swelling)  Only volume of IF is increased, not of other compartments ― Can impair tissue function by increasing distance for diffusion of oxygen and nutrients from blood into cells Could be caused by increased fluid flow out of blood or decreased return of fluid to blood © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Central Role of Sodium in Fluid and Electrolyte Balance  Sodium is most abundant cation in ECF  Only cation exerting significant osmotic pressure is Na+ Controls ECF volume and water distribution because water follows salt Changes in Na+ levels affects plasma volume, blood pressure, and ECF and IF volumes  There are no known receptors that monitor Na+ levels in body fluids  Na+-water balance is linked to blood pressure and blood volume control mechanisms  Changes in blood pressure or volume trigger neural and hormonal controls to regulate Na+ content © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Sodium Balance (cont.)  Influence of aldosterone and angiotensin II (cont.) Renin catalyzes production of angiotensin II ― Prompts aldosterone release from adrenal cortex ― Results in increased Na+ reabsorption by kidney tubules Aldosterone release is also triggered by elevated K+ levels in ECF Aldosterone brings about its effects slowly (hours to days) © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.8 Mechanisms and consequences of aldosterone release. Body Na+ content K+ concentration triggers renin release, in the ECF increasing angiotensin II Stimulates Adrenal cortex Releases Aldosterone Targets Kidney tubules Effects Na+ reabsorption K+ secretion Restores Homeostatic plasma levels of Na+ and K+ © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Sodium Balance (cont.)  Influence of atrial natriuretic peptide (ANP) Released by atrial cells in response to stretch caused by increased blood pressure Effects ― Decreases blood pressure and blood volume  Inhibits ADH, renin, and aldosterone production  Increases excretion of Na+ and water © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.9 Mechanisms and consequences of ANP release. Stretch of atria of heart due to BP Releases Negative feedback Atrial natriuretic peptide (ANP) Targets Granular cells Hypothalamus and Adrenal cortex of the kidney posterior pituitary Effects Effects Renin release* ADH release Aldosterone release Angiotensin II Inhibits Inhibits Collecting ducts of kidneys Vasodilation Effects Na+ and H 2O reabsorption Results in Blood volume Results in Blood pressure © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Sodium Balance (cont.)  Influence of other hormones Female sex hormones ― Estrogens: increase NaCl reabsorption (like aldosterone)  Leads to H2O retention during menstrual cycles and pregnancy ― Progesterone: decreases Na+ reabsorption (blocks aldosterone)  Promotes Na+ and H2O loss Glucocorticoids ― Increase Na+ reabsorption and promote edema © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 26.10 Mechanisms regulating sodium and water balance help maintain blood pressure homeostasis. Systemic blood pressure/volume Stretch in afferent Filtrate NaCl concentration in Inhibits baroreceptors arterioles ascending limb of nephron loop in blood vessels (+ ) (+ ) (+ ) (+ ) Sympathetic Granular cells of kidneys nervous system Release (+ ) Renin Systemic arterioles Catalyzes conversion Causes Angiotensinogen Angiotensin I Vasoconstriction (from liver) Results in Converting enzyme (in lungs) Peripheral resistance (+ ) Angiotensin II Posterior pituitary (+ ) (+ ) (+ ) Releases Systemic arterioles Adrenal cortex ADH (antidiuretic hormone) Causes Secretes (+ ) Vasoconstriction Aldosterone Collecting ducts Results in Targets of kidneys Causes Peripheral resistance Distal kidney tubules H2O reabsorption Causes Na+ (and H2O) reabsorption Results in Blood volume (+ ) stimulates Renin-angiotensin-aldosterone Blood pressure mechanism Neural regulation (sympathetic nervous system effects) ADH release and effects © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Potassium Balance  Importance of potassium Affects resting membrane potential (RMP) in neurons and muscle cells (especially cardiac muscle) ― Increases in ECF [K+] (hyperkalemia) cause decreased RMP, causing depolarization, followed by reduced excitability ― Decreases in ECF [K+] (hypokalemia) cause hyperpolarization and nonresponsiveness Disruption in [K+] (hyper- or hypokalemia) in heart can interfere with electrical conduction, leading to sudden death © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Potassium Balance (cont.)  K+ is also part of body’s buffer system  H+ shifts in and out of cells in opposite direction of K+ to maintain cation balance, so: ECF K+ levels rise with acidosis ECF K+ levels fall with alkalosis  Regulatory site: the DCT and collecting duct K+ balance is controlled in cortical collecting ducts by regulating amount secreted into filtrate Kidneys have limited ability to retain K+, so most K+ is lost in urine; may lead to deficiency if not replaced in diet © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 16.12 Effects of parathyroid hormone on bone, the kidneys, and the intestine. Hypocalcemia (low blood Ca2+) PTH release from parathyroid gland Osteoclast activity Ca2+ reabsorption Activation of in bone causes Ca2+ in kidney tubule vitamin D by kidney and PO43– release into blood Ca2+ absorption from food in small intestine Initial stimulus Physiological response Ca2+ in blood Result © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Regulation of Anions  Cl– is major anion accompanying Na + in ECF Helps maintain osmotic pressure of blood 99% of Cl– is reabsorbed under normal pH ― Passively follows Na+ in PCT and is coupled to active transport of Na+ in other tubule segments  When acidosis occurs, fewer chloride ions are reabsorbed in lieu of HCO3– © 2016 Pea rs on Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  26.4 Acid-Base Balance  pH affects all functional proteins and biochemical reactions, so it is closely regulated by the body  Normal pH of body fluids Arterial blood: pH 7.4 Venous blood and interstitial fluid: pH 7.35 ICF: pH 7.0  Alkalosis or alkalemia: arterial pH >7.45  Acidosis or acidemia: arterial pH