renal 8 Flashcards
what are the compositions of the ICF
- High protein, K, phosphate
- low Na and Cl
- K is the MOST IMPORTANT intracellular cation
- ANIONS = phosphates and proteins
what are the composition of the ECF
- main extracellular cation is Na
- Main anion is Cl
- plasma contains less proteins than ICF, but higher than interstitial fluid does
How does the size/osmolality change with the ingestion of pure water?
- ECF would become diluted and hypotonic
- water would enter the ICF space and dilute the space until it was about the same as ECF
- overall effect is to reduce osmolality of both compartments and increase compartment size
How does the size/osmolality change with the ingestion of isotonic water (saline)
- ECF compartment alone would expand
how does the size/osmolality change with the ingestion of hypertonic water (saline)
- ECF osmolality would increase greatly initially and fluid would be drawn from cells into the ECF to lower the tonicity
- ICF volume is contracted and cells shrink
- ECF volume increases and overal osmolality increases
Define Ineffective osmole
- high extracellular concentration of a solute that easily crosses membranes, but would do so rather than draw water out of the ICF of the osmoreceptor
- RESULT: lowers extracellular osmotic pressure and increase it intracellularly
explain why elevated plasma urea concentrations do not elicit ADH release
- raised urea would not elicit an ADH response
how do plasma osmolality and baroreceptor signals control the release of ADH
- INCREASE in osmolality extracellularly causes shrinkage of the osmoreceptor which causes the release of ADH from posterior pituitary
- baroreceptors exist in low pressure areas and sense BP
- -> LOW BP = INCREASE ADH
how do plasma osmolality and baroreceptor signals affect thirst
- Thirst is caused by shrinkage of osmoreceptors (increased ECF osmolality)
- a large decrease in blood volume or pressure would cause thirst
- -> Angiotension II affects the brain and increases thirst
What are the alterations that occur when excess NaCl ingestion occurs in salt sensitive individuals
- Na/K pumps keep Na in the ECF and draws fluid out of the cell –> leads to increase in BP
- Increase BP DECREASES renal sympathetic nerve action and thus DECREASES RENIN SECRETION
- DECREASED RENIN –> causes decreased reabsorption of Na in proximal tubule
- DECREASED RENIN also means LESS angiotensin I, II and thus LESS aldosterone –> less vasoconstriction, Na reabsorption and thirst
- ALDOSTERONE WOULD stimulate Na reabsorption but it is DECREASED
describe the body’s response to sudden decrease in plasma/blood volume due to hemorrhage
- DECREASED BP –> increases renin –> increased angiotensin II –> more water and Na reabsorbed and less excreted
describe the effects of ADH on the kidney
- Binds to vasopression type II receptors on collecting ducts –> insertion of aquaporins which increase lumen permeability to water
- ADH vasoconstricts pericytes around vasa recta and decrease blood flow (preserves medullary gradient and concentrate urine)
- ADH increases urea permeability of medullary collecting ducts
