Water, Electrolyte & Acid-Base Balance
What concentration of H+ indicates the pH?
- High H+ ions concentration in the solution the lower the pH - Low H+ ions concentration in solution the higher the pH
What are the main electrolytes in the ECF and ICF?
-Na, Cl, Ca higher in blood plasma then in cells -K and Pi higher in cells (ICF) Blood osmolarity is 300
Renal control of pH?
1) H+ in blood reacts with HCO3 to form H2CO3 2) H2CO3 decomposes to H2O and CO2, which enter renal tubule cell 3) reforms as H2CO3 4) H2CO3 ionizes to form HCO3 which goes back to blood and H+ 5) Na+/ H+ antiport exchange H+ for Na+ and Na+ in and H+ out of cell 6) H+ reacts with HCO3 to form H2CO3 in tubular fluid 7) brush border of renal cells decomposes H2CO3 to H2O and CO2 again and H+ is eliminated into H2O in urine
What is the reaction if bicarbonate buffer system?
CO2 + H2O <-> H2CO3 <-> HCO3 + H+ reversible reaction - if proceeds to the right carbonic acid is wk acid and releasing H+ lowering pH -if proceeds to the left, carbonic acid is wk base and binds H+ and removes it to raise pH
What does electrolyte balance do?
Condition when the quantities of electrolytes entering the body equal those leaving it - participate in chemical reactions - determine electrical potential across cell membranes -affect osmolarity of body fluids and affects water distribution - affect acid-base balance of body fluid
Dehydration, thirst, and rehydration process
Dehydration is an increase in blood osmolarity dehydration occurs -stimulates an increase in blood osmolarity -stimulates hypothalamic osmoreceptors -reduction in salivation causing dry mouth -causing a sense of thirst -stimulating ingestion of water (short-term thirst) -rehydrates blood (long-term thirst)
What are some disorders from fluid sequestration
Edema - accumulation of fluid in the interstitial spaces Hematomas - hemorrhage into tissues, removes fluid from circulatory Pleural effusions - fluid accumulate in pleural cavity during infection & removes from circulatory system
What is sodium and what hormones affect Na+ concentration?
Excretion of dietary excess - need 0.5 g/day yet we get 3-7 g/day in diet Aldosterone - increases number of renal Na/K pumps in ascending limb, DCT, and CD ADH - increases aquaporins and water reabsorption and reducing Na+ concentration ANP - inhibits secretion of renin, aldosterone and ADH, and excretes more Na+ & water which decreases BP
What is calcium?
Functions: skeletal mineralization, muscle contraction, 2nd messenger - cells like to maintain low intracellular Ca+ lvls to prevent Ca+ / phosphate crystal precipitation so cells will pump Ca+ out
What is the phosphate buffer system?
H2PO4- <-> HPO42- + H+ phosphortic acid and hydrogen phosphate Important in the ICF and renal tubules -where phosphate levels are more concentrates and pH is closer to pH 6.8 - proceed to the right to free H+ and lower pH or proceed to the left to bind to H+ and raise pH
Acid base disorder in metabolism
Metabolic acidosis - increase in organic acids or overuse of acidic drugs and loss of base Metabolic alkalosis - overuse of bicarbonate and loss of acids
What is potassium and some of its functions?
Most abundant cation of ICF - Na/ K pump: a role in co-transport of solutes and heat production - 90% of K+ in glomerular filtrate is reabsorbed by the PCT - when blood K+ is high leads to aldosterone secretion and DCT and CD secrete K+ into urine, aldosterone regulates its homeostasis
What hormones regulate calcium?
Parathyroid hormone (PTH): increases blood calcium levels-increases urinary phosphate excretion
What role does electrolyte play?
Play a role in water distribution and total water content -Na in ECF & K in ICF
Acid base disorder in respiratory
Respiratory acidosis - can occur with emplysema which causes lungs not being able to expel enough CO2 Respiratory alkalosis - cause hyperventilation, CO2 eliminated faster than produced
What is a buffer?
a substance that minimizes changes in pH physiological buffer - system that controls output of acids and bases or CO2, works in urinary and respiratory system Chemical buffer - weak acid and weak base, removes H+ from sol'n or relases H+ into sol'n when needed
What is the protein buffer system?
accounts for 75% of all chemical buffering in the body fluids - acidic side group can release H+ when pH is too high to lower it -COOH -> COO- + H -Amino side groups can bind H+ when pH is low and can raise it NH2 + H -> NH3
What does dehydration affect?
affects all fluid compartments - affects circulatory shock, neuron shrinkage, infant mortality
What is hyperkalemia?
effects depend in rate of imbalance, can occur in two origins, outward difussion of K+ is reduced from cell: -Rapid onset : such as during a crush injury, damages cells release high lvls of K+ in cells vs K+ leaving cells. Results in more excitable nerves and muscle cells leading to cardiac arrest -Slow onset: such as renal failure or decrease in aldosterone will disrupt repolarization phase (outputs of K+ is slow) leading the to less excitable nerves and muscle cells leading to slow HR
What is hypokalemia?
from sweating, chronic vomiting, diarrhea - cause K+ to diffuse out of cell causing negative K+ state in the cell and cells are hyperpolarized ( excessive K+ channels opening) causing nerve and muscle cells to be less excitable - results in muscle weakness, loss of muscle tone, and decrease in reflexes
What is hypercalcemia?
high calcium from alkalosis, hyperparathyrdoism or hypothyrdoism -decrease membrane Na+ permeability and inhibits depolarization - high Ca+ leads to muscular weakness, depressed reflexes, cardiac arrest
What causes fluid excess and sequestration?
kidney failure, aldosterone & ADH hypersecretion
What is hypocalcemia?
low calcium from low vitamin D, diarrhea, pregnancy, hypoparathyroidism, hyperthyroidism -increase membrane Na+ permeability which increases excitable nerve and muscle cells -leading to tetanus, laryngospasm or death
What is hyponatremia?
low sodium levels in blood plasma sodium is < 130mEg/ L - usually result of excess body water and leads to cell swelling and edema
Respiratory control of pH
neutralizes 2 to 3 times as much acid as chemical buffers can - Increase CO2 in blood and causes a decrease in pH stimulate and an increase pulmonary ventilation to blow off CO2 and moving to become more basic -Increase pH results inhibits pulmonary ventilation and allows CO2 to accumulate and shift more acidic
What is an acid and a base?
pH of a solution is determines by its hydrogen ions Acid- chemicals that releases H+ in a solution to lower pH, proton donor Base - chemicals that accepts H+ or binds to raise pH, proton acceptor
Compensation for pH imbalances?
respiratory compensation - Fast and limited, low pH leads to increase in ventilation, high pH leads to decrease ventilation to allow CO2 to build up renal compensation - slow yet powerful can compensate for urine pH, in acidosis increase in H secretion by renal tubule and alkalosis is bicarbonate secretion
What is the bicarbonate buffer system?
solution of carbonic acid and bicarbonate ions - pH of 6.1 , functions well in body due to respiratory and uriary system - raise in pH, lungs excrete CO2 and keep rnx moving - lower pH, kidneys excreted HCO3-
How is water output regulated?
via aldosterone and ADH Aldosterone : responses to a decrease in BP or a decrease in Na and stimulates adrenal cortex to secrete aldosterone - Increases Na and water reabsorption and increases BP and K+ excretion ADH: responses to dehydration and stimulates water uptake to blood through aquaporins and decrease urine volume and urine secretion
What is fluid deficiency?
volume depletion - (hypovolemia) deficit in extracellular fluid volume due to water and sodium lost, caused by hemorrhages, sever burns, vomiting or diarrhea dehydration - an increase in blood osmolarity due to decrease in drinking water, diabetes which increases urine secretion, increase sweating, increase in diuretics
What is water balance?
when water intake equals water output - Adults are 50-60% water with fluid compartments -65% in cells of ICF and 35% outside cell ECF
