regulation of the urinary system Flashcards
what do the kidneys need to make sure is balanced?
maintain water-salt and acid-base balance
excrete waste and foreign substance
what are other functions of the kidneys?
produce erythropoietin which is involved in RBC production
regulates blood pressure through the RAAS
regulates blood glucose level (gluconeogenesis)
how do the kidneys maintain homeostasis?
regulate blood volume
regulate ion composition in blood
regulate plasma pH and blood pH
regulate blood solute concentration
how is urea formed? (waste)
through breakdown of amino acids in the liver
how is uric acid produced? (waste)
by the breakdown of nucleic acids
how is creatinine produced? (waste)
muscle cells breaking down creatine phosphate
what are the healthy characteristics of urine?
pH 6
95% water
1.2 L per day
clear yellow
no bacterial content
solutes include: electrolytes, urea, creatinine, uric acid etc
what drives glomerular filtration?
glomerular hydrostatic pressure forces plasma out of capillary
what goes against filtration?
hydrostatic pressure in bowman’s space, colloid osmotic pressure (result of proteins in the glomerular capillary)
how do you calculate net glomerular filtration pressure?
take the hydrostatic pressure of the capillary and subtract the colloid osmotic pressure of the blood added to the hydrostatic pressure of Bowman’s capsule.
what happens to the glomerular filtration rate if the glomerular net filtration pressure decreases?
it will decrease
what happens if blood flow in the glomerulus increases?
the GFR and GFP also increase
what happens when the GFR and the GFP decrease?
the kidney will secrete hormones to restore it back to normal (RAAS)
what is the renin-angiotensis-aldosterone system?
it regulates blood pressure. cells of the macula densa stimulate cells in the juxtamedullary apparatus to release renin into the blood.
renin is also released in response to low sodium/chloride ion concentration
renin catalyses reactions for angiotensin II
A II causes vasoconstriction of blood vessels and aldosterone release
aldosterone increases reabsorption of sodium ions and water from the filtrate by the renal tubules.
the result increases blood volume and blood pressure.
what happens if blood pressure is too high?
the atrial natriuretic peptide opposes effect of angiotensin II.
high [Na+] detected by atria, ANP secreted
ANP inhibits release of aldosterone
low aldosterone lvls = Na+ reabsorption prevented
this leads to increase in water and Na+ secretion
how is the volume and concentration of urine regulated?
by the control of water reabsorption
what are the two ways water reabsorption can be controlled?
by osmosis along the PCT and descending loop of Henle
or by the ADH hormone in distal tubes or collecting ducts. in the presence of ADH, water is retained by the kidneys
what is the role of the antidiuretic hormone?
to prevent excessive water loss in urine and increases in water reabsorption
how does ADH do this?
stimulates insertion of aquaporins in the apical membrane, more water is transported into cells.
