Chapter 13 Excretion (new)排泄.ppt

Solute Diuresis = osmotic diuresis （渗透性利尿） large amounts of a poorly reabsorbed solute such as glucose, mannitol (甘露醇） , or urea Osmotic Diuresis Poorly reabsorbed Osmolyte H20 H20 H20 Na Na Na H20 H20 H20 Na Na Na Hypotonic Saline Osmolyte = glucose, mannitol, urea Glomerulotubular Balance Concept: The constant fraction (about 65% - 70%) of the filtered Na+ and water are reabsorbed in the proximal tubular, despite variation of GFR. Importance: To prevent overloading of the distal tubular segments when GFR increases. Glomerulotubular balance acts as a second line of defense to buffer the effect of spontaneous changes in GFR on urine output. (The first line of defense discussed above includes the renal autoregulatory mechanism, especially tubuloglomerular feedback, that help to prevent changes)  The hypothalamus contains two types of neurons that synthesize ADH in the supraoptic nucleus and paraventricular nucleus. Once ADH is synthesized, it is transported down the axons of the neurons to their tips, terminating in the posterior pituitary gland. -----synthesized and storage sites Antidiuretic hormone ( ADH 抗利尿激素) 2. Nervous-Humonal control of the tubular function Secretion of ADH Increased osmolarity ADH Post. Pituitary Urge to drink STIMULUS cAMP + The most important renal action of ADH is to increase the water permeability of the distal tubule, collecting tubule. This effect helps the body to conserve water in circumstances such as dehydration 脱水. ------- Function of ADH ADH Combine with the receptor in basolateral membrane activate the adenylate cyclase Produce cyclic adenosine monophosphate ( cAMP) Activate the protein kinase in the membrane Phosphorylate the membrane protein change the configuration of membrane Increase the permeability to water by the open of water channel