Body Fluids, Water-Salt & Acid-Base Balance (BIO310) PDF

BODY FLUIDS, WATER-SALT & ACID BASE BALANCE BIO310 / Acid-base balance / NHM  LESSON OUTCOMES 1. Body Fluids Describe the different types of fluids in the body 2. Water-salt balance Explain ADH systems Explain the RAAS 3. Acid-base balance Describe the functions of kid...

BODY FLUIDS, WATER-SALT & ACID BASE BALANCE BIO310 / Acid-base balance / NHM  LESSON OUTCOMES 1. Body Fluids Describe the different types of fluids in the body 2. Water-salt balance Explain ADH systems Explain the RAAS 3. Acid-base balance Describe the functions of kidney in acid-base balance BIO310 / Acid-base balance / NHM  INTRODUCTION Maintenance of normal volume and normal composition of the extracellular fluid is vital to life. 3 types of homeostasis are involved in this maintenance: a) fluid balance b) electrolyte balance c) acid-base balance. Exchange occurs between the ICF and ECF. BIO310 / Acid-base balance / NHM  FLUID COMPARTMENT Body fluids includes water and solutes. About 2/3 of the body’s fluid is located within cells and is called intracellular fluid (ICF). The other 1/3 called extracellular fluid (ECF). Extracellular fluid (ECF) – consists of two major subdivisions a) Plasma – the fluid portion of the blood b) Interstitial fluid (IF) – fluid in spaces between cells. 1/3 2/3 BIO310 / Acid-base balance / NHM Figure 15.8 The major fluid compartments of the body. Total body water Volume = 40 L 60% body weight Plasma Volume = 3 L, 20% of ECF Interstitial Intracellular fluid (ICF) fluid (IF) Volume = 25 L Volume = 12 L 40% body 80% of ECF weight Extracellular fluid (ECF) Volume = 15 L 20% body BIO310 / Acid-base balance / NHM weight WATER WATER BALANCE BALANCE BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  SOURCES OF WATER Sources of water: Preformed water: 2,300 ml Drinking water: 1,500 ml (60%) Moist food : 750 ml (30%) Water of metabolism: 250 ml (10%) Cellular respiration Dehydration synthesis BIO310 / Acid-base balance / NHM  Sources of water loss Through kidneys in urine - 1500 ml (60%) Through intestines - 150 ml (6%) Can be significant in vomiting and diarrhea From skin (sweat) - 150 ml (6%) From lungs and skin - 700 ml (28%) Last is called insensible loss (menstruation) BIO310 / Acid-base balance / NHM  Regulation of Water & Salt Through regulating urine formation a) Antidiuretic hormone (ADH) : causes water reabsorption b) Aldosterone : causes sodium (and water) to be reabsorbed c) ANP (atrial natriuretic peptide) : causes sodium (and water) loss when pressure in is too high. “Where sodium goes, water follows” BIO310 / Acid-base balance / NHM  2) Renin-Angiotensin-Aldosterone 1) Antidiuretic hormone (ADH) System (RAAS) BIO310 / Acid-base balance / NHM One hormone important in regulating water balance is antidiuretic hormone (ADH). [Diuretic: substance tend to increase flow of urine] ADH: produced in the hypothalamus of the brain stored in and released from the pituitary gland osmoreceptor cells in the hypothalamus monitor the osmolarity of the blood. BIO310 / Acid-base balance / NHM Osmolarity rises - more ADH is released into the bloodstream and reaches the kidney. ADH induces the epithelium of the HIGH: Osmolarity distal tubules and collecting ducts to become more permeable to water. Increase water reabsorption - reduces urine volume. Produced concentrated urine. Osmolarity Water ADH Level (High Na+) reabsorption BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  Renin-angiotensin-aldosterone system (RAAS) Juxtaglomerular apparatus (JGA), located near the afferent arteriole. Between renal corpuscle and returning distal tubule. Regulate: Blood volume LOW: blood pressure 🗉 Blood volume - Blood pressure When blood pressure or blood volume in the afferent arteriole drops, the enzyme renin initiates chemical reactions that convert a plasma protein angiotensinogen to a peptide called angiotensin II. BIO310 / Acid-base balance / NHM  Acting as a hormone, angiotensin II increases blood pressure and blood volume in several ways: 1❖ It raises blood pressure by constricting arterioles, decreasing blood flow to many capillaries, including those of the kidney. 2❖ It also stimulates the adrenal glands, located atop the kidneys, to release a hormone called aldosterone. ❖ This acts on the distal tubules, which reabsorb Na+ and water, increasing blood volume and pressure. BIO310 / Acid-base balance / NHM  Aldosterone Aldosterone regulate concentration of sodium (Na+) and potassium (K+): Reabsorb sodium (Na+) Secrete potassium (K+) BIO310 / Acid-base balance / NHM  REGULATION OF SODIUM BALANCE : ALDOSTERONE High aldosterone: cause ↑ Na absorption – water follow + concentrated urine. Low aldosterone: cause Na+ excretion and water will follow diluted urine. BIO310 / Acid-base balance / NHM Figure 15.12 Flowchart of mechanisms regulating sodium and water balance to help maintain blood pressure homeostasis. Falling systemic blood pressure/volume (+) Reduced filtrate volume Inhibits Hypothalamic or solute content in baroreceptors osmoreceptors renal tubules in blood vessels (+) (+) (+) (+) Sympathetic nervous Posterior pituitary JG cells of kidneys system Release (+) Release ADH (antidiuretic Systemic arterioles hormone) Causes (+) Renin Vasoconstriction Collecting ducts Leads to of kidneys Results in Causes Peripheral resistance Angiotensin II formed in blood H2O reabsorption (+) (+) (+) Systemic arterioles Adrenal cortex Causes Secretes Vasoconstriction Aldosterone Results in Targets Peripheral Kidney tubules resistance Causes Na+ reabsorption (and H2O absorption) KEY: Results in (+) = stimulates Blood volume Renin-angiotensin system Neural regulation (sympathetic nervous system effects) Rising blood pressure Effects of ADH release BIO310 / Acid-base balance / NHM Overview of Hormonal control of the kidney by negative feedback circuits BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  COMPOSITION OF BODY FLUIDS Water is the universal solvent Solutes are broadly classified into: Electrolytes – inorganic salts, all acids and bases, and some proteins. Nonelectrolytes – examples include glucose, lipids, creatinine, and urea. BIO310 / Acid-base balance / NHM  ELECTROLYTE Chemicals that dissolve in water and dissociate into positive and negative ions (including inorganic salts, acids and bases). Electrolytes have greater osmotic power than nonelectrolytes. help to create the osmolarity of body fluids and therefore regulate the movement of water between compartments. Water is attracted to electrolytes, especially Na+. Osmotic pressure – a pressure of the tendency for the solution to gain water by osmosis (often Na+) BIO310 / Acid-base balance / NHM  ELECTROLYTE Water will move from a compartment with a low concentration of electrolytes to one with a high concentration of electrolytes = OSMOSIS Cations – positive ions Na+ (sodium) - most abundant cation in the ECF; essential for electrical activity of nerve and muscle cells. The level of Na+ is regulated primarily by the kidneys. BIO310 / Acid-base balance / NHM  ELECTROLYTE Sodium holds a central position in fluid and electrolyte balance. Sodium salts: ~90-95% of all solutes in the ECF (280/300 mOsm ECF solute concentration). Sodium is the single most abundant cation in the ECF, the only cation exerting significant osmotic pressure. Changes in plasma sodium levels affect: Plasma volume, blood pressure ICF and interstitial fluid volumes BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  ELECTROLYTE Cations K+ (potassium) - most abundant cation in the ICF; essential for electrical activity of nerve and muscle cells. Ca2+ (calcium) - mostly in bones & teeth; essential for blood clotting; maintains normal nerve and muscle cell function. Mg2+ (magnesium) - more abundant in ICF than ECF; essential for ATP production and activity of nerve and muscle cells. BIO310 / Acid-base balance / NHM  ELECTROLYTE Anions – negatively charged ions. Cl- (chloride) - most abundant anion in the ECF. HCO3- (bicarbonate) – part of the bicarbonate buffer system. HPO42- (phosphate) Proteins- - (negatively charged proteins) inside the cell and in plasma regulate water in those compartments and play a role in regulating electrolyte distribution. BIO310 / Acid-base balance / NHM  ELECTROLYTE CONCENTRATION BIO310 / Acid-base balance / NHM  NON-ELECTROLYTE Non-electrolytes – most organic compounds that do not ionize (dissociate) in solution, ex. glucose. ▪ These compounds do contribute to the osmolarity. BIO310 / Acid-base balance / NHM ACID BASE BALANCE BIO310 / Acid-base balance / NHM  ACID-BASE BALANCE Regulation in the concentration of free hydrogen ions (H+) in the body fluids. Acids dissociate in solution to form free hydrogen ions. strong acid (HCl) – have a greater tendency to do this. weak acid (bicarbonate) – less tendency to dissociate. The normal pH of blood fluid arterial blood – 7.4 venous blood and IF – 7.35 ICF – 7.0 BIO310 / Acid-base balance / NHM  ACID-BASE BALANCE Normal pH 7.35 – 7.45 Alkalosis or alkalemia – arterial blood pH rises above 7.45. Acidosis or acidemia – arterial pH drops below 7.35 (physiological acidosis). BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM SOURCES OF HYDROGEN IONS Most hydrogen ion originate from cellular metabolism. Breakdown of phosphorus-containing proteins releases phosphoric acid into the ECF. Anaerobic respiration of glucose produces lactic acid. Fat metabolism yields organic acids and ketone bodies. Transporting CO2 as bicarbonate releases hydrogen ions. BIO310 / Acid-base balance / NHM SOURCES OF HYDROGEN IONS BIO310 / Acid-base balance / NHM  HYDROGEN ION REGULATION Concentration of hydrogen ions is regulated sequentially by: a. Chemical buffer systems – act within seconds. b. The respiratory center – acts within 1-3 minutes. c. Renal mechanisms – require hours to days to effect pH changes. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  CHEMICAL BUFFER SYSTEMS One or two molecules that act to resist pH changes when strong acid or base is added. Three major chemical buffer systems a. Bicarbonate buffer system b. Phosphate buffer system c. Protein buffer system Any drifts in pH are resisted by the entire chemical buffering system. BIO310 / Acid-base balance / NHM  BICARBONATE BUFFER SYSTEMS A mixture of carbonic acid (H2CO3) and its salt, sodium bicarbonate (NaHCO3) ; (potassium or magnesium bicarbonates work as well). If strong acid is added: Hydrogen ions released combine with the bicarbonate ions and form carbonic acid (a weak acid). The pH of the solution decreases only slightly. HCl + NaHCO3 H2CO3 + NaCl BIO310 / Acid-base balance / NHM  BICARBONATE BUFFER SYSTEMS If strong base is added: It reacts with the carbonic acid to form sodium bicarbonate (a weak base). The pH of the solution rises only slightly. NaOH + H2CO3 NaHCO3 + H2O This system is the only important ECF buffer. BIO310 / Acid-base balance / NHM  PHOSPHATE BUFFER SYSTEMS Nearly identical to the bicarbonate system. Its components are: Sodium salts of dihydrogen phosphate (H2PO4), a weak acid. Monohydrogen phosphate (HPO42¯), a weak base. HCl + Na2HPO4 NaH2PO4 + NaCl NaOH + NaH2PO4 Na2HPO4 + H2O This system is an effective buffer in urine and ICF where phosphate concentrations are high. BIO310 / Acid-base balance / NHM  ELECTROLYTE CONCENTRATION BIO310 / Acid-base balance / NHM PROTEIN BUFFER SYSTEMS Plasma and intracellular proteins are the body’s most plentiful and powerful buffers. Some amino acids of proteins have: Organic acid groups (weak acids) –COOH (carboxyl). R-COOH ---RCOO- + H+ Groups that act as weak bases –NH2 (amino). R-NH2---R-NH3 Amphoteric molecules are protein molecules that can function as both a weak acid and a weak base. BIO310 / Acid-base balance / NHM  PHYSIOLOGICAL BUFFER SYSTEMS The respiratory system regulation of acid-base balance is a physiological buffering system. There is a reversible equilibrium between: Dissolved carbon dioxide and water. Carbonic acid and the hydrogen and bicarbonate ions CO2 + H2O ↔ H2CO3↔ H+ + HCO3- BIO310 / Acid-base balance / NHM  Physiological buffer MECHANISM OF ACID-BASE BALANCE Chemical buffers can tie up excess acids or bases, but they cannot eliminate them from the body. Physiological buffer: The lungs can eliminate carbonic acid (volatile acid) by eliminating carbon dioxide. Only the kidneys can rid the body of metabolic acids (phosphoric, uric, and lactic acids and ketones) and prevent metabolic acidosis. The ultimate acid-base regulatory organs are the kidneys. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM RENAL MECHANISM OF ACID- BASE BALANCE Alkaline blood Secrete bicarbonate ions. Gain hydrogen ions. Acidic blood Reabsorb bicarbonate ions. Secrete hydrogen ions. H+ secretion occurs in the proximal tubule and in the collecting ducts. H+ come from the dissociation of carbonic acid. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  RENAL MECHANISM OF ACID- BASE BALANCE The most important renal mechanisms for regulating acid-base balance are: Conserving (reabsorbing) or generating bicarbonate ions. Excreting bicarbonate ions. Losing a bicarbonate ion is the same as gaining a hydrogen ion; reabsorbing a bicarbonate ion is the same as losing a hydrogen ion Reabsorption of Bicarbonate Carbonic acid formed in filtrate dissociates to release carbon dioxide and water Carbon dioxide then diffuses into tubule cells, where it acts to trigger further hydrogen ion secretion For each hydrogen ion secreted, a sodium ion and a bicarbonate ion are reabsorbed by the PCT cells Secreted hydrogen ions form carbonic acid Thus, bicarbonate disappears from filtrate at the same rate that it enters the peritubular capillary blood BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM Generating New Bicarbonate Ions Two mechanisms carried out by tubule cells generate new bicarbonate ions Both involve renal excretion of acid via secretion and excretion of hydrogen ions or ammonium ions (NH4+) BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM Acid-Base Imbalances Respiratory acidosis Respiratory alkalosis Metabolic acidosis Metabolic alkalosis BIO310 / Acid-base balance / NHM  RESPIRATORY & RENAL COMPENSATIONS Acid-base imbalance due to inadequacy of a physiological buffer system is compensated for by the other system. The respiratory system will attempt to correct metabolic acid-base imbalances. The kidneys will work to correct imbalances caused by respiratory disease. BIO310 / Acid-base balance / NHM  RESPIRATORY ACIDOSIS AND ALKALOSIS Result from failure of the respiratory system to balance pH. PCO2 is the single most important indicator of the respiratory inadequacy. PCO2 The partial pressure of CO2 (the amount of carbon dioxide gas dissolved in the blood); PCO2 ↑, blood pH ↓ Normal PCO2 levels : 35-45 mm Hg. BIO310 / Acid-base balance / NHM  RESPIRATORY ACIDOSIS pH below 7.35. Carbonic acid excess caused by blood levels of CO2 above 45 mm Hg. Hypercapnia – high levels of CO2 in blood. It is the most common cause of acid-base imbalance. Occurs when a person breathes shallowly, pneumonia, cystic fibrosis, or emphysema. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3- BIO310 / Acid-base balance / NHM  BODY COMPENSATION Compensation: Kidneys eliminate H+ and retain HCO3- BIO310 / Acid-base balance / NHM RESPIRATORY ALKALOSIS pH above 7.45. pCO2 below 35 mm Hg. Respiratory alkalosis is a common result of hyperventilation. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  BODY COMPENSATION Compensation: Kidneys conserve H+ and eliminate HCO3-. BIO310 / Acid-base balance / NHM  METABOLIC ACIDOSIS pH below 7.35. Bicarbonate ion levels below 22 mEq/L. Is the second most common cause of acid-base imbalance. Causes: Ingestion of too much alcohol, excessive loss of bicarbonate ions, accumulation of lactic acid, shock, ketosis in diabetic crisis, diarrhea, starvation, and kidney failure. Symptoms: headache, vomiting, diarrhea. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  BODY COMPENSATION Compensation: Increase ventilation Kidneys conserve HCO3- and eliminate H+. BIO310 / Acid-base balance / NHM METABOLIC ALKALOSIS Blood pH above 7.45. ▪ Bicarbonate excess concentration in the blood is greater than 26 mEq/L. ▪ Typical causes are: Vomiting of the acid contents of the stomach. Intake of excess base (e.g., from antacids). Constipation, in which excessive bicarbonate is reabsorbed. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM  BODY COMPENSATION Compensation: Suppressed breathing Kidneys conserve H+ and eliminate HCO3-. BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM BIO310 / Acid-base balance / NHM THANK YOU.. BIO310 / Acid-base balance / NHM