Urinary Systems and Electrolytes V

Pregunta	Respuesta
Function of CC multiplier	Concentrate urine in LOH
Initial concentration of CCM	Walls of AL impermeable to water Walls of DL permeable Osmotic gradient
Single effect generation	A.T./Diffusion of NaCl out of AL to ISF Dilutes tubule fluid, conc.'s ISF H2O from DL to hyperosmotic ISF Diffusion of Na/Cl to DL
The single effect	Dif in OSP and [Nacl] btw. ALF/DLF/ISF H2O moves out of DL to ISF until =
How does OSP' change in nephron	OSP' increases as depth into medulla increases
What does length of LOH determine?	OSP' size and conc. of urine
What is the vasa recta?	Specialised capillary of juxtamedullary nephron
What is the function?	Creates a hyperosmotic ISF to draw as much water out of nephron as possible Especially during antidiuresis
Salt diffusion from VR	DVR: plasma ~300 mOsm Encounters ^ osmotic ISF as it descends Salt diffuses from ISF to plasma, ^ its conc AVR: Conc. blood flows towards cortex from papilla loses salt to increasingly dilute medullary ISF
Summary	Salt reabsorbed from LOH trapped+recycled within medulla by CC flow of blood in vasa recta
Water reabsorption in VR	DVR: Dilute blood flow into medulla loses H2O to ^ conc. medullar ISF AVR: Conc. blood flow from tip of papilla towards cortex gains H2O from ^ dilute medullary ISF
Summary	Water tends to short circuit from DVR-> AVR helps preserve conc. of medullary ISF
Diagram of urea movement	ah
Where is [urea] high	interstitium of inner medulla
Why does inner medulla have a steep osmotic '?	Facilitate constant reabsorption of H2O from DL This maintains a high conc. of tubular fluid in DCT/CD, concentrating urine
Urea Uniporters	Expressed in CD facilitates diff of urea from intertubular -> ISF Further ^ OSP of ISF of inner medulla Further ^ H2O reabsorption
Hormonal control Vasopressin (ADH)	Upregulates urea uniporter expression of UT-A1/UT-A3
UT-A2	Expressed in LOH, passes urea from ISF to intertubular fluid
Vasopressin	Produced in hypothalamus Released by pituitary gland ^ H2O permeability of DCT/CD ^ BP as more h2o reabsorped Decreases blood plasma osmolarity
How does ADH do this?	Upregulates translocation of AQP channels to apical PCM of DCT/CD cells
What happens when dehydrated	When dehydrated less H2O available to be reabsorbed, urine more conc., more ADH released to ^ H2O reabsorption
Renin	Creates Angiotensin I from angiotensin Converted to Angiotensin II Stimulates adrenal cortex to produce aldosterone Aldosterone ^ Na+ reabsorption Angiotensin II also stimulates General Systemic Vasoconstriction
Stimulators of renin secretion	Low BP Low Na+ in DCT, sensed by Maculla Densa SNS

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Urinary Systems and Electrolytes V

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