BM1042 Lecture Notes - Lecture 12: Extracellular Fluid, Collecting Duct System, Macula Densa
Document Summary
Discuss how the renal system contributes to the control of fluid in the body. Extrinsic mechanisms: change glomerular hydrostatic pressure in the face of overall demands from the body (usually large loss of blood volume, neural, baroreceptor reflex constricts afferent arterioles, hormonal. Jcg responds to decreased blood pressure, sns innervation and macula densa to release renin. Urine concentration: normal human = 1ml/min isotonic urine, overhydrated = 25ml/min hypotonic urine, dehydrated = 0. 3ml/min hypertonic urine, medullary gradient allows production of urine of varying concentrations. Medullary concentration gradient: exists only in renal medulla. If dilute urine - cd is relatively impermeable to water so water stays in cd -> dilute urine. If conc urine - due to adh, insertion of water channels, fluid in cd is exposed to conc gradient in intersitial fluid, as fluid moves down cd more water drawn into interstitial fluid due to conc gradient. Fluid remaining in cd becoming more concentration as more water leaves.
