Renal Physiology Flashcards
What are the functions of the kidneys?
regulates blood pressure. produces erythryopoietin which is vital in rbc production. maintains calcium and phosphase balance via nephrons and vit D activation. maintains acid/base and electrolyte balance. removal of waste products such as urea, creatinine, drugs and toxins.
What is the nephron and function of urine formation?
the nephron forms urine, which contributes to filtration, tubular reabsorption and secretion.
What is the glomerular membrane and its function?
they are cells lining the visceral membrane of the Bowman’s capsule. it is the membrane/barrier for filtrations, which lines the capillaries, the basement membrane carries a -ve charge. permeability is selective and is dependent on size and charge.
What is the role of the sympathetic nervous system with renal blood flow regulation?
there is a balance between the opposing filtrations of glomerular and bowman’s hydrostatic pressure and glomerular and bowman’s colloidal osmotic pressure. they are responsible for pushing water out and pulling it back in. the filters are plasma without the proteins, which are big and negative.
What is the renin-angiotensin-system and how does it relate to renal blood flow?
a drop in bp and fluid volume results in a release of renin, which acts on angiotensinogen to form angiotensin 1. angiotensin converting enzyme (ACE) releases from lungs and acts on angiotensin 1 to form angiotensin 2. this acts on the adrenal gland to stimulate the release of aldosterone which acts on the kidneys to stimulate reabsorption of salt and water. it also acts on blood vessels stimulating vasoconstriction.
How does the ultrafiltration coefficient affect glomerular filtration rate.
determined by SA and permeability of glomerular membrane.
inc SA = inc Kf = inc GFR, proportional
relaxation of mesangial cells (contractile cells found between efferent and afferent arterioles. eg ANP, PGE2, cAMP, dopamine
dec SA…
dec no glomerular capillaries, eg uncontrolled diabetes. contraction of mesangial cells, eg norepinephrine, vasopressin, thromboxane A2, endothelins, leucotrins A and D, PGF2, histamine
inc thickness = dec Kf = dec GFR
uncontrolled diabetes and hypertension.
How does glomerular capillary hydrostatic pressure affect glomerular filtration rate.
determined by diameter of afferent and efferent arterioles, and arterial bp.
vasodilation: inc HPg = inc GFR
bradykinis, PG12, PGF2. moderate vasodilation = angiotensin 2.
vasoconstriction: dec HPg = dec GFR
sympathetic stimulation. severe vasoconstriction = dec renal blood flow.
inc arterial BP = inc renal blood flow = inc HPg = inc GFR
buffered by autoregulatory mechanisms such as tubuloglomerular feedback and myogenic autoregulation
How does bowman’s capsule hydrostatic pressure affect glomerular filtration rate.
inc HPb = dec GFR
caused by stone in ureter
How does glomerular colloidal osmotic pressure affect glomerular filtration rate.
inc PIg = dec GFR
dehydration
dec PIg = inc GFR
hypoproteinemia
What is plasma clearance?
the volume of plasma that is completely cleared of the amount of substance excreted in urine per min.
How does the nephron regulate fluid and electrolyte balance in the body?
water and electrolytes are reabsorbed by peritubular capillaries by bulk flow.
What is tubular transport maximum?
max rate at which a substance can be transported by renal tubules. only actively transported substances have Tm-limited transport rate due to saturation of specific carrier and enzyme systems involved in active transport. Tm limited reabsorption (glucose, amino acids, phosphates, sulfates). Tm limited secretion (para-aminohippuric acid PAH, penicillin)
What is the renal threshold?
the plasma concentration is below where none of the substances appear in urine, it is completely reabsorbed.
How is Na+ handled by the renal tubule in reabsorption and secretion?
99% or more of filtered Na+ is reabsorbed along the renal tubule. glucose, amino acids, phosphates, calcium, chlorides, water absorption and hydrogen secretion is handled by the proximal convoluted tubule. reabsorption in the distal convoluted tubuyle is dependent on aldosterone, and stimulates transcription of proteins for channels.
How is glucose reabsorbed?
it is freely filtered and follows the transport maximum. once it is reached, excretion starts and happens earlier due to renal threshold.
