Intro to Renal Physiology Flashcards
what are the five regulatory functions of the kidney?
managing extracellular fluid volume, osmolarity and ion composition, clearing metabolic end products, toxins and drugs and endocrine functions
describe the kidney’s support of cardiovascular function?
it maintains adequate blood pressure and blood flow y regulating volume
what percentages of body weight are total body water, intracellular fluid and extracellular fluid?
TBW is 60%, ICF is 40% and ECF is 20%
how many L is in 1 kg?
one
what percentage of ECF is intravascular vs extravascular?
intra- 25%, extra 75%
how does total body fluid change with age?
it decreases with age due to shrinkage of extracellular fluid volume
how does total body water relate to total body fat?
it is inversely proportional
how do solute composition and concentration compare in the ICF and ECF?
composition is very different but the concentration is the same (300 mOsm/L)
T or F: kidneys and GI tract are the only effector organs that contribute to regulation of fluid balance.
F- kidneys are the only effector organs in regulation of fluid and water balance
where does unregulated awater and salt loss come from?
sweat, feces and insensible skin and lung loss
what are the four starling forces?
capillary and tissue hydrostatic pressure
capillary and tissue oncotic pressure
why are ions and total osmotic pressure not included in the starling forces?
because ions can readily flow into and out of the vasculature with water
what is the equation for filtration or reabsorption rate? what is Lp and where is it high in the body?
rate= Lp[(Pc-Pi)-(PIc-PIi)]
Lp is the hydraulic conductivity coefficient (high in glomerulus)
what is the interplay between the hydrostatic pressure and oncotic pressure gradients in a normal capillary? what trend of fluid flow does this result in?
hydrostatic forces drive fluid out and oncotic forces drive fluid in. because of the initial filtration of the capillary, there is resorption at the end of the capillary because of the decrease in hydrostatic pressure that has occurred
compare the solute distribution between the ISF and plasma?
they are similar for everything except negatively charged plasma proteins in the vasculature. this drives fluid from the ECF inwards
what is gibbs donnan equilibrium?
the electrochemical equilibrium between the ISF and ESF caused by larger proportion of negatively charged proteins in the vasculature. this causes more cations to diffuse inwards and less anions to do so
dysfunction of what four organ systems causes edema?
cardiac, renal, hepatic and endocrine
how does edema correspond to weight?
increase in edema indicated by a weight increase
how do nephrotic syndrome and liver disease contribute to edema?
both decrease the intravascular protein concentration and therefore capillary oncotic pressure
what system maintains edema? how?
the renin- angiotensin- aldosterone system
the decrease in renal perfusion pressure activates it and increases sodium retention
what forces contribute to movement of water into and out of cells?
only osmotic pressure differences across the plasma membrane
how is water typically moved into and out of a cell?
by transportation of solutes. water then follows down its concentration gradient
what are the effects on ICF and ECF with isotonic IV fluid gain? what is the effect on vascular fluid?
ICF: no osmotic change or volume change
ECF: no osmotic change but increased volume
vascular- dilution of plasma proteins and RBC
what are the effects on ICF and ECF with isotonic fluid loss like diarrhea? what is the effect on vascular fluid?
ICF: no osmotic change or volume change
ECF: no osmotic change but decreased volume
vascular- concentration of plasma proteins and RBC
what are the effects on ICF and ECF with profuse sweating or water deprivation?
ICF: increased osmolarity and decreased volume
ECF: increased osmolarity and decreased volume
what are the effects on ICF and ECF with excessive salt intake without fluids? what buffers this change initially?
ICF: increased osmolarity and decreased volume
ECF: increased osmolarity and increased volume
increased cellular uptake of the excess sodium consumed
why is Na uptake not a sufficient buffering system for reducing fluid loss with high salt intake without fluid?
because a high intracellular Na concentration increases the availability of sodium for the Na/K pump to extrude, increasing its kinetics
what are the effects on ICF and ECF with inappropriate antidiuretic hormone availability? why does this happen?
ICF: decrease osmolarity and increased volume
ECF: decreased osmolarity and increased volume
occurs because there is an increase in water resporption in the kidney
what are the effects on ICF and ECF with adrenal insufficiency? why does this happen?
ICF: decrease in osmolarity and increased volume
ECF: decreased osmolarity and decreased volume
decreases in salt reuptake in the kidney decrease the ECF osmolarity
what is the main cause of difference in solute composition of the ICF and ECF?
the Na/K pump in the membrane of cells maintaining a low intracellular sodium concentration and a high potassium concentration
what is the response to cell shrinking or swelling associated with placement in a solution of differing osmolarity?
solute influx or efflux respectively to allow water to re enter (regulatory volume increase) or exit the cell (regulatory volume decrease)
why should a physician be cautious when attempting to restore ECF osmolarity to normal rapidly?
because there has been regulatory volume changes, the cells now have the same osmolarity as the surrounding solution at normal cell volume. by changing that drastically the cells could dangerously swell or shrink
what are the four basic renal processes and what is not included as one of these?
filtration, resorption, secretion and synthesis
excretion is not included because it is the result of the above processes
how do ultrafiltrate solutes compare to plasma? to urine?
has about the same ion concentration as plasma
this is modified before it turns into urine
what is the difference between renal reabsorption and secretion?
reabsorption is movement of solutes and water out of the renal tubule
secretion is the movement of solutes ONLY into the renal tubule
what does synthesis refer to in the kidney?
degrades ammonium, makes bicarbonate, renin, erythropoetin and activates vit D
what is the formula for excretion?
excretion = filtered + secreted + synthesized - reabsorbed
what is the renal “handling” of solutes?
what the nephron does with filtered water and solute. is considered for each individual solute
what are the two examples of water transport?
filtration (driven by hydrostatic pressure difference) and osmosis (dfiven by osmotic gradient)
what are the two examples of solute transport?
active transport and passive diffusion
compared to the amount of water filtered out of the plasma per day, how much is excreted? what causes the variability in this number?
180 L filtered, 0.5-12 L excreted per day
varies depending on how much water is consumed
what signals direct the regulation of ECF by the kidneys? how is this carried out?
neural and hormonal signals
water and solute reabsorption are both regulated
