Fluid-Electrolyte & Acid-Base Balance Chapter 19

Water Compartments  Fluid compartments  Intracellular fluid—about 2/3 of total  Extracellular fluid—plasma, lymph, tissue fluids  Cerebrospinal fluid in central nervous system, synovial fluid in joints, aqueous humor of eye, serous fluids between organs & membranes  Fluid compartments  Intracellular fluid—about 2/3 of total  Extracellular fluid—plasma, lymph, tissue fluids  Cerebrospinal fluid in central nervous system, synovial fluid in joints, aqueous humor of eye, serous fluids between organs & membranes

Movement of Water  Water moves via two processes  Filtration  Osmosis

Fluid compartments Figure 22-1

Water Intake & Output  Intake: 2500 ml/day  Oral liquids: 1600 ml/day (about 6½ 8 oz glasses)  Food: 700 ml/day (about 3 glasses)  Internal source: 200 ml (less than 1 glass)

Water Intake & Output  Output: 2500 ml/day  Urine 1500 ml/day  Sweat 500 ml/day  Exhaled water vapor 300 ml/day  Feces 200 ml/day  Intake & output SHOULD BE EQUAL  Sweating, vomiting or diarrhea: DRINK MORE  Too much intake: urinate more

Intake and output Figure 22-2 Intake of water Output of water

Regulation Hypothalamus of brain Hypothalamus of brain Regulates water content Regulates water content Osmolarity—concentration of dissolved materials in a fluid Osmolarity—concentration of dissolved materials in a fluid Osmoreceptors in hypothalamus detect changes in blood osmolarity Osmoreceptors in hypothalamus detect changes in blood osmolarity

Regulation of Body Water If body is dehydrated If body is dehydrated Osmolarity of blood increases Osmolarity of blood increases Less fluid in body makes body fluids more concentrated Less fluid in body makes body fluids more concentrated Person feels thirsty & drinks fluids for relief Person feels thirsty & drinks fluids for relief Water absorbed by intestines Water absorbed by intestines Osmolarity of blood decreases Osmolarity of blood decreases

Regulation of Water ADH (antidiuretic hormone) ADH (antidiuretic hormone) Produced by hypothalamus, stored in posterior pituitary Produced by hypothalamus, stored in posterior pituitary Function: tells kidneys to save (reabsorb) water to relieve dehydrated state Function: tells kidneys to save (reabsorb) water to relieve dehydrated state Result: less urine is produced Result: less urine is produced

Regulation of Water Aldosterone Aldosterone Produced by adrenal cortex Produced by adrenal cortex Function: tells kidneys to conserve (reabsorb) water to relieve a lowered blood pressure or a lowered blood Na + level Function: tells kidneys to conserve (reabsorb) water to relieve a lowered blood pressure or a lowered blood Na + level

Regulation of Water Water intoxication—lowers concentration of dissolved materials Water intoxication—lowers concentration of dissolved materials Blood volume & blood pressure increase Blood volume & blood pressure increase Atria natriuretic peptide (ANP) from heart Atria natriuretic peptide (ANP) from heart Function: tells kidneys to excrete Na + & water to lower BP & blood volume Function: tells kidneys to excrete Na + & water to lower BP & blood volume

Electrolytes  Electrolytes are formed when molecules in water dissociate  Electrolytes are either positive or negative  Positive ions are called cations  Na +, K +, Ca 2+  Negative ions are called anions  Cl -, HCO 3 -, HPO 4 2-

Electrolytes Most are inorganic molecules Most are inorganic molecules Salts (NaCl, KCl, CaCl) Salts (NaCl, KCl, CaCl) Acids (H 2 CO 3 or HCl) Acids (H 2 CO 3 or HCl) Bases (NaHCO 3 or Na 2 HPO 4 ) Bases (NaHCO 3 or Na 2 HPO 4 ) Are part of tissues like bones, muscle & nerves Are part of tissues like bones, muscle & nerves Are part of proteins like enzymes or insulin Are part of proteins like enzymes or insulin

Electrolytes Help to establish the osmolarity of body fluids Help to establish the osmolarity of body fluids AND, their presence helps regulate an important process AND, their presence helps regulate an important process Movement of water: osmosis Movement of water: osmosis Water moves to attempt at diluting concentrated fluids Water moves to attempt at diluting concentrated fluids Moves from LOW concentration to HIGH Moves from LOW concentration to HIGH

Electrolytes  K + is most predominant ICF cation (remember “KICK”)  Na + is most predominant ECF cation (remember “NECK”)  Cl - is most predominant anion in ECF  Few protein anions found in tissue fluid  Many protein anions found in plasma  HPO 4 -2 (phosphate) & protein anions are found in ICF

Regulation of Electrolytes We eat & drink these molecules daily We eat & drink these molecules daily We lose these in urine & feces but also in sweat We lose these in urine & feces but also in sweat Sweat is mostly NaCl (ever taste it??) Sweat is mostly NaCl (ever taste it??) Electrolytes end up in urine if there is too much of that substance in the blood Electrolytes end up in urine if there is too much of that substance in the blood

Regulation of Electrolytes  Hormonal regulation  Aldosterone:  Increases Na + reabsorption (conservation) by kidneys  Increases K + excretion by kidneys  Urine ends up with less Na + but more K + in it

Regulation of Electrolytes  ANP  Increases excretion of Na + by kidneys  Urine has more Na+ ions in it  Parathyroid (PTH)  Increases Ca 2+ & P reabsorption from bones into blood  Results in weaker bones & increased values of both ions in blood

Regulation of Electrolytes Calcitonin Calcitonin  Increases Ca 2+ & P removal from blood (into bones)  Results in lowered blood values of both ions & stronger bones

Acid-Base pH scale

Acid-Base Balance Normal blood pH: 7.35 – 7.45 (slightly alkaline) Normal blood pH: 7.35 – 7.45 (slightly alkaline) ICF is slightly acidic: 6.8 – 7.0 ICF is slightly acidic: 6.8 – 7.0 Tissue fluid pH is closer to blood but varies Tissue fluid pH is closer to blood but varies pH scale: 7.0 is neutral pH scale: 7.0 is neutral Acidic: pH < 6.99 Acidic: pH < 6.99 Alkaline: pH > 7.01 Alkaline: pH > 7.01

Buffers Recall: substances that are able to deflect drastic changes in body pH Recall: substances that are able to deflect drastic changes in body pH Consist of weak acid, weak base Consist of weak acid, weak base When they react with STRONG acid or STRONG base, the resultant substance have little effect on overall pH of body When they react with STRONG acid or STRONG base, the resultant substance have little effect on overall pH of body 3 systems in body: bicarbonate, phosphate & protein systems 3 systems in body: bicarbonate, phosphate & protein systems

Bicarbonate system Recall: weak acid (H 2 CO 3 ) & weak base (NaHCO 3 ) Recall: weak acid (H 2 CO 3 ) & weak base (NaHCO 3 ) Each easily dissociates in blood plasma, ready to give up or take up H + ions whenever the need exists Each easily dissociates in blood plasma, ready to give up or take up H + ions whenever the need exists

Adding HCl to body HCl + NaHCO 3  NaCl + H 2 CO 3 Salt (NaCl) has no effect on pH Salt (NaCl) has no effect on pH Weak acid (H 2 CO 3 ) makes little change to pH Weak acid (H 2 CO 3 ) makes little change to pH

Adding Sodium Hydroxide to body NaOH + H 2 CO 3  H 2 O + NaHCO 3 Water has no effect on pH Water has no effect on pH Weak base (NaHCO 3 which is sodium bicarbonate) has little effect on pH. Weak base (NaHCO 3 which is sodium bicarbonate) has little effect on pH.

Phosphate System Phosphate system—sodium dihydrogen phosphate (NaH 2 PO 4 ), a weak acid & sodium monohydrogen phosphate (NaHPO 4 ), a weak base. Phosphate system—sodium dihydrogen phosphate (NaH 2 PO 4 ), a weak acid & sodium monohydrogen phosphate (NaHPO 4 ), a weak base. Adding strong acid does not have major effect on pH (NaCl = no effect on pH) Adding strong acid does not have major effect on pH (NaCl = no effect on pH) Adding strong base does not have major effect on pH (water = no effect on pH) Adding strong base does not have major effect on pH (water = no effect on pH) HCl + NaHPO 4  NaCl + NaH 2 PO 4 NaOH + NaH 2 PO 4  H 2 O + NaHPO 4

Protein Buffer System Important in ICF Important in ICF Amino acids may act as either acid or base Amino acids may act as either acid or base Carboxyl (COOH) can act as an acid & donate H+ ions to  pH Carboxyl (COOH) can act as an acid & donate H+ ions to  pH Amine group (NH 2 ) can act as a base & pick up extra H+ ions to  pH Amine group (NH 2 ) can act as a base & pick up extra H+ ions to  pH React immediately but little long-term capacity React immediately but little long-term capacity

Respiratory Regulation of pH Can regulate CO 2 in body by increasing or decreasing respiratory rate Can regulate CO 2 in body by increasing or decreasing respiratory rate CO 2 Can form H 2 CO 3 with water in body fluids; H + ion affects pH CO 2 Can form H 2 CO 3 with water in body fluids; H + ion affects pH CO 2 + H 2 O  H 2 CO 3  H+ + HCO 3 -

Respiratory Regulation of pH Respiratory Acidosis Respiratory Acidosis CO 2 (waste product) is retained in system CO 2 (waste product) is retained in system Occurs with respiratory diseases (pneumonia, emphysema, asthma) Occurs with respiratory diseases (pneumonia, emphysema, asthma) Any decrease in respiratory rate or breathing efficiency Any decrease in respiratory rate or breathing efficiency Excess H+ ions are produced by reaction on previous slide Excess H+ ions are produced by reaction on previous slide This lowers pH of body fluids This lowers pH of body fluids

Respiratory Regulation of pH Respiratory Alkalosis Respiratory Alkalosis Usually caused by hyperventilation Usually caused by hyperventilation Less common Less common Exhale too much CO 2 Exhale too much CO 2 Fewer H+ ions are produced Fewer H+ ions are produced Result in rise in body fluid pH Result in rise in body fluid pH

Respiratory Compensation— Metabolic Acidosis Caused by kidney disease, diabetic ketoacidosis, excessive diarrhea or vomiting Caused by kidney disease, diabetic ketoacidosis, excessive diarrhea or vomiting Respiratory rate  in response Respiratory rate  in response Exhale more CO 2, less H + ion produced Exhale more CO 2, less H + ion produced pH increases back up toward normal pH increases back up toward normal

Respiratory Compensation— Metabolic Alkalosis Not common, caused by overingestion of antacids or vomiting of stomach contents only Not common, caused by overingestion of antacids or vomiting of stomach contents only Respiratory rate slows breathing Respiratory rate slows breathing Exhale LESS CO 2 (more retained) Exhale LESS CO 2 (more retained) More H+ ions produced, result is lowering of pH in body fluids back to normal More H+ ions produced, result is lowering of pH in body fluids back to normal Works within a few minutes Works within a few minutes

Respiratory system control of pH

Renal Mechanisms Best ability for long-term control of pH in acidosis situation Best ability for long-term control of pH in acidosis situation Take hours to days to reach full capacity Take hours to days to reach full capacity Compensating for acidosis: will excrete H + ions, conserve Na + & HCO 3 - ions Compensating for acidosis: will excrete H + ions, conserve Na + & HCO 3 - ions Compensating for alkalosis: will excrete Na+ & HCO 3 - ions while conserving H + ions Compensating for alkalosis: will excrete Na+ & HCO 3 - ions while conserving H + ions

Compensation First line is ECF buffers First line is ECF buffers Bicarb, phosphate and protein Bicarb, phosphate and protein Second line is respiratory system Second line is respiratory system Breathing rate  to exhale more CO 2, to  H + formation (which would lead to acidic pH) Breathing rate  to exhale more CO 2, to  H + formation (which would lead to acidic pH) This  is limited, however This  is limited, however Lastly, renal system Lastly, renal system Keep patient alive Keep patient alive Excrete H + ions in urine (urine very acidic) Excrete H + ions in urine (urine very acidic)

Manifestations of Acidosis & Alkalosis Acidosis: depression of nerve transmissions results in confusion & disorientation, finally coma, death Acidosis: depression of nerve transmissions results in confusion & disorientation, finally coma, death Alkalosis: irritability, muscle twitches & progression leads to severe muscle spasms & convulsions. Alkalosis: irritability, muscle twitches & progression leads to severe muscle spasms & convulsions.