Fluid/Electrolyte Balance Flashcards
volume, concentration and pH of ECF and ICF are stabalized by
-fluid balance
-electrolyte balance
-acid base balance
what are electrolytes
-ions released through idssociation of inorganic compounds
-can conduct electrical current in solution
electrolyte balance
-when gains and losses for every electrolyte are in balance
-primarily involves balancing rates of absorption across digestive tract with rates of lsos at kidneys
what does acid base balance actually balcne
0production and loss of hydrogen ions
kidney and lung effects on acid base balance
-kidneys secrete H+ into urine and generate buffers that enter the bloodstream
-lungs affect pH through elimantion of CO2
4 principles of regulation of fluids and electrolytes
-all homeostatic mechanisms that monitor and adjust body fluid composition respond to changes in the ECF not ICF
-no receptors directly monitor fluid or electrolyte balance, they monitor plama volume and osmotic concentration
-cells cannot move water by active transport
-body wate or electrolyte content willrise or fall accroding to diet
primary hormones that regulate fluid and electrolye balance
-ADH
-aldosterone
-natriuretic peptides
ADH
-stimulste conservation of water at kidneys
-concentrTes urine
-stimulates hypothalamic thirst center promoting fluid intake
ADH production and release
-osmoreceptors in hypothalamus monitor osmotic concentration of ECF
-release ADH near fenestration capillaries in posterior lobe of Pit. gland
-higher osmotic concentration increases ADH release
aldosterone function
-secreted by adrenal cortex
-rising K or falling Na levels in blood
-determines rare of Na reabsorption and K loss in the kidneys
high aldosterone plasma concentration
-conservation of sodium
-water retention
-water follows salt
-more K in urine
natuietic peptides
-ANP and BNP
-released by cardiac muscle cells in response to abnormal stretching of heart walls
-reduce thirst
-block release of ADH and aldosterone
-causes diruesis (fluid loss by kidneys)
-lower blood pressure and plasma volume
what are electrolyes in body fluids measured in
-equivalents - amount of positive or negative ion that supplies 1 mol of electrical charge
general rules of electrolye balancee
-most common issues are associated with imabalance of sodium
-problems with K balance are less common but more dangerous than sodium
hyponatremia
-body water content rises
-soidum concentration of ECF is <135mEq/L
hypernatreimia
-water content declines
-sodium concentration of ECF >145mEq/L
what happens if ECF volume is inadequate
-blood volume and blood pressure decline
-RAAS system activated
-water and Na losses reduced
-Water and Na gains are increased
-ECF volume increases
if plasma volume is too large what happens
-venous return increases stimulating release of ANP and BNP
-reduces thirst
-block secretion of ADH and aldosterone
-salt and water loss at kidneys
-ECF volume decreases
dominant cation in ICF
-potassium
-ICF concentration = 160
-ECF concentration = 3.5-5.5
potassium balance
-98% of potassium in body is in ICF
-cells use energy to to recover potassium from ECF–> cytoplasm
-concentration of ECF is a balance between gaining though digestive tract and loss in urine
potassium losses in urine
-regulated by activities of ion pumps along DCT and collecting system
-Na from tubular fluid are exchanged for K in peritubular fluid
-limited gained from digestive system
factors affecting rate of K secretion into urine
-changes in K concentration in ECF
-changes in pH
-aldosterone levels
hypokalemia
-deficiency of K in blood stream
hyperkalemia
-elevated level of K in bloodstream
why does H+ get secreted in exchange for Na+ in peritubular fluid instead of K+ when there is a low pH of ECF
to remove excess H+ ions to restore pH balance
aldosterone effects on potassium balance
-affect urinary losses
-ion pumps sensitive to aldosterone reabsorb Na from tubular fluid in exhange for K+ from peritubular fluid
-high plasma K stimulates aldosterone
-K lost in the urine as a result
major factors involved in distubances of K ion balance
-
acids bases and salts
-acids: gives up H+ when dissociates
-bases: gives up ions that combine with H+ when dissociates
-Salts: compound with cation, not H+ and anion not OH-
acidosis
-abnormally low blood pH
-acidemia is when blood pH <7.35
alkalosis
-physiological state resulting from abnormally high blood pH
-blood pH higher than 7.45
what systems to alkilosis and acidosis
particularly nervous and cardiovasciular systems
-acidosis more common
-because normal cellular activities geenrate acids
carbonic anhydrase
-enzyme that catalyzes formation of carbonic acid from carbon dioxide and water
-found in : cytoplasm of RBC
-Liver and kidney cells
-parietal cells or stomach
-many other cells
what is the most important factor affecting blood pH
-PP of CO2
what does most Co2 insolution convert to
-carbonic acid
PCO2 and pH relationship
-when CO2 levels rise H+ and HCO3 are released and pH decreases
-at alveoli CO2 diffuses into atmosphere, H+ and HCO3 in alveolar capillaries decrease and blood pH rises
buffers
-dissolved compounds that stabalize pH of solution by adding or removing H+
-buffer system consists of a weak acid that donate H+ an anion that acts as a weak base
three major buffer systems
-phosphate buffer system
-protein buffer systems
-Carbonic acid and bicarbonate buffer system
carbonic acid bicarbonate buffer system
-prevents changes in pH caused by metabolic acids and fixed acids in ECF
limitations to buffer systems
-provide only temporary solution to acid base imbalance
-do not eliminate H+
-supply of buffer molecules is limited
to preserve homeostasis captured H+ must be
-permantently tied up in water molecules through CO2 removal at lungs
-removed from body fluids by secretion at kidneys
how do respiratory and renal mechanisms support buffer systems
-secreting or absorbing H+
-controlling excretion of acids and bases
-generating additional buffers
respiratory compensation
-increasing or decreasing rate of respiration alters pH by lowering or raising PCO2
where are hydrogen ions secreted into tubular fluid along
-PCT
-DCT
-collecting system
buffers in urine
-required to eliminate large # of H+
-glomerular filtration provides compoennts of Carbonic acid bicarbonate buffer system and phosphate buffer system
-Tubule cells of PCT generate ammonia and contribute to the ammonia buffer system
renal response to acidosis
-secretion of H+
-Activity of buffers in tubular fluid
-removal of CO2
-reabsorbtion of NaHCO3
renal responses to alkalosis
-rate of H+ secretion at kidneys declines
-tubule cells do not reclaim bicarbonate ions in tubular fluid
-colelcting system transports HCO3 into tubular fluid while releasing H+ and Cl- into peritubular fluid
