physioex 9

• glomerular capillary pressure: forced fluid through endothelium of capillaries into lumen of surrounding Bowman's capsule
• from Bowman's capsule filtrate move into rest of renal tubule for processing
• glomerular filtration rate: index of kidney function, 80-140ml/min or 180L of filtrate every 24hrs
• decreasing afferent arteriole radius decreased the glomerular capillary pressure and filtration rate and increasing raidu increased those factors
• decreasing efferent arteriole radius increased both capillary pressure and filtration rate while increasing the radius decreased both
• caffeine dilates afferent arterioles as it also increases urine formation
• when in the desert ad dehydrating afferent constriction and efferent dilation would be the most beneficial as the filtration rate and pressure drop would better conserve water
• starling forces: hydrostatic and osmotic pressure gradient
• unusually high hydrostatic blood pressure in glomerular capillaries promotes filtration
• increase in blood pressure leads to increase in urine volume due to high filtration rate
• increased blood volumes causes increased blood pressure so increasing urine formation helps to stabilize blood pressure and volume
• when collecting duct and urinary bladder duct were closed the pressure increased but the filtration rate decreased; to overcome greater pressure was needed
• afferent arteriole resistance alters the GFR
• renal tubule length does not have a significant impact on GFR
• normally glomerular capillary pressure and filtration are relatively constant despite blood pressure changes because nephron can alter afferent and efferent arteriole radii
• increasing afferent radius and decreasing efferent radius increased GFR
• blood pressure drop, afferent dilates and efferent constricts to maintain normal GFR
• increasing afferent radius in low b.p. returned the GFR to almost baseline values
• efferent constriction improved low pressure and filtration marginally during low bp
• afferent dilation was more effective than efferent dilation for glomerular filtration rate during low blood pressure
• ADH increases water permeability of collecting duct
• renal reabsorption

  • water and solutes from tubule lumen then interstitial space and then peritubular capillaries
• the kidneys reabsorb water through the use of ADH to create concentrated urine
• carrier proteins present in PCT absorbs glucose through secondary active transport at apical membrane then facilitated diffusion at tubule cell basolateral membrane
• glucose is carriers remove glucose out of the urine but when a transport max is reached then it is disposed through urine
• aldosterone decreased urine volume as it trigger reabsorption of sodium from filtrate to body and potassium excretion, leading to water following that gradient
• when aldosterone and ADH are together it increases blood pressure as the concentration gradient of solutes and water increases = increased urine concentration
• ADH creates a more concentrated urine with a low volume than aldosterone
• want to reabsorb sodium ions without increasing blood volume?

  increase aldosterone and decrease ADH
• decreased arteriole pressure releases renin which becomes angiotensin II and aldosterone in secreted to promote more sodium in and more potassium out