Slows filtrate production Decreased filtration rate resulting in decreased

Slows filtrate production decreased filtration rate

This preview shows page 12 - 15 out of 22 pages.

Slows filtrate production Decreased filtration rate resulting in decreased filtrate production:1.Dilates afferent arterioles, constricts efferent arterioles 2.Increases GHP and GFR 3.Increases filtrate production 26-5: Countercurrent multiplication, antidiuretic hormone, and aldosterone affect reabsorption and secretion Reabsorption and SecretionReabsorption: recovers useful materials from filtrateSecretion: ejects waste products, toxins, and other undesirable solutesBoth occur in every segment of nephron except renal corpuscleRelative importance changes from segment to segmentReabsorption and Secretion at the PCTThe PCT is the location of MOST REABSORPTIONPCT cells normally reabsorb 60–70%of filtrate produced in renal corpuscleReabsorbed materials enter peritubular fluid and diffuse into peritubular capillaries to return to circulationFunctions of the PCT:-Reabsorption of organic nutrients-Reabsorption of water-Reabsorption of ions (passive and active) -SecretionSodium Ion Reabsorption:Important in every PCT processIons enter tubular cells by-Diffusion through leak channels-Sodium-linked cotransport of organic solutes-Countertransport for hydrogen ionsReabsorption and Secretion at the Nephron LoopThe nephron loop reabsorbs about 1/2 of the water and 2/3 of sodium and chloride ions remaining in tubular fluidCountercurrent Multiplication: the exchange that occurs between the two parallel limbs of loop of Henle Countercurrent-Refers to exchange between tubular fluids moving in opposite directions12
Background image
-Fluid in descending limb flows toward renal pelvis-Fluid in ascending limb flows toward cortexMultiplication-Refers to effect of exchange-Increases as movement of fluid continuesLimb PermeabilityParallel segments of nephron loop are very close together, separated only by peritubular fluidThey have very different permeability characteristicsThe Thin, Descending Limb:Only permeable to waterImpermeable to solutesThe Thick, Ascending Limb:Impermeable to water and solutesContains active transport mechanisms (pumps)-Pump Na+ and Cl-from tubular fluid into peritubular fluid-Elevates osmotic concentration in peritubular fluid around descending limb-Cause osmotic flow of water out of descending limb into peritubular fluid-*Creates a positive Feedback LoopoSolute pumping at ascending limb increases solute concentration in descending limboFluid then arrives in the ascending limboAccelerates Na+and Cl-pumping into peritubular fluidoMore water is reabsorbed Countercurrent Multiplication Active transport at apical surface moves Na+, K+and Cl-out of tubular fluid and into peritubular fluidUses a carrier protein called Na+-K+/2 Cl-Transporter (Sodium Potassium 2 Chloride transporter): Each cycle moves 1 sodium ion, 1 potassium ion, and 2 chloride ions Potassium Ions:Potassium ions are pumped into peritubular fluid by cotransport carriers13
Background image
Background image
Image of page 15

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture