BCMB 230 1st Edition Lecture 23 Outline of Last Lecture I Ion Gradients and Osmotic Pressure in Nephron II Juxtaglomerular Apparatus III Regulation of Blood Calcium Level IV Regulation of H pH in Plasma Outline of Current Lecture I Plasma pH Regulation II Reabsorption and Secretion III Bicarbonate Handling pH in the Kidney IV Digestive System Current Lecture I Plasma pH Regulation Change in hydrogen ion concentration buffer prevents pH change until buffering capacity is reached then buffering does not continue to work Acidosis H increase pH decrease respiratory hypoventilation increase CO2 decrease pH can also be caused by a decrease in lung surface lung damage or if there is a lot of CO 2 in the air being breathed in metabolic prolonged diarrhea production of nonvolatile acids through cellular processes Alkalosis H decrease pH increase respiratory hyperventilation decrease CO2 increase pH metabolic prolonged vomiting loss of H utilization of H ions in cellular processes Metabolic issues from actions of tissues throughout the body can happen in muscle lactic acid metabolism in tissues digestive system throwing up from the kidney stomach acid neutralized in intestines with bicarbonate from pancreas in the liver lose intestinal content through diarrhea chronic happens for a long time If problem is respiratory there can be a temporary fix with the kidney renal compensation problem in lungs fix it in the kidneys If problem is metabolic temporary patch is respiratory compensation problem is metabolic fix it with the lungs Metabolic acidosis too much H These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute hyperventilate respiratory compensation get rid of CO2 Metabolic alkalosis too little H hypoventilate respiratory compensation have more CO2 Respiratory renal compensation for respiratory acidosis increase bicarbonate reabsorption by tubular metabolism in kidney increase bicarbonate production in kidney increase secretion of H ions Respiratory renal compensation for respiratory alkalosis response is weak don t have a strong physiological response to this II Reabsorption and Secretion Filtrate in tubules tubular cells interstitial fluid peritubular capillary with blood in it Tight junctions between cells help to localize protein on one side versus the other of the membrane Epithelial cells have two sides apical luminal surface and basolateral surface luminal side side of the cell making up the inside of the tubule basolateral side side of cell in contact with the interstitial fluid Na K ATPase on basolateral surface pumps K into cell Na out of the cell interstitial fluid has higher concentration of Na than K Have various transporters on luminal side ion channels transport K out of cell lots of Na into cell via diffusion cell interior has high concentration of K than Na Reabsorb Na Na K ATPase pumps Na out Na levels drop K increase in cell open up ion channels lets Na come in and K out don t have to have pump on both sides of membrane make sure you are moving things in right direction Na K pump can t be reversed Glucose reabsorption linked with Na absorption Na does not come through channels uses a cotransporter with glucose just need facilitated diffusion transporter to let it out Reabsorption of water Na K ATPase on basolateral surface cause decrease in osmolality of cell water can come into the cell if tight junctions are a little leaky increase Na concentration can get paracellular transport control this through channels or aquaporins channels for water activated by ADH increases permeability have vasopressin activate adenylate cyclase makes cAMP cAMP independent pathway causes vesicle containing aquaporins to be inserted in the membrane new proteins put into the membrane III Bicarbonate Handling pH in the Kidney Largely tubular metabolism which is chemical reactions happening in the kidney within renal tubules have enzyme carbonic anhydrase takes carbon dioxide and water to produce carbonic acid which ionizes into bicarbonate and hydrogen ion have different proteins on luminal apical and basolateral membrane hydrogen ion pump ATPase make sure hydrogen ions get moved out into filtrate move hydrogen ions into filtrate secretion transporter for bicarbonate facilitated diffusion transport move H out and into blood make new carbonate and move into plasma H in filtrate binds to carbonate changes to bicarbonate turns into water and carbon dioxide don t have enzyme Call this reabsorption through tubular metabolism take bicarbonate destroy it make new one and move into plasma net result is same thing as if it were reabsorbed actually bicarbonate reabsorption through tubular metabolism Can make new bicarbonate two mechanisms for making bicarbonate from CO2 take CO2 and water carbonic anhydrase bicarbonate goes one way hydrogen goes another way not reabsorption because hydrogen ion interacts with phosphate buffer not bicarbonate call this production of bicarbonate through CO2 from glutamine amino acid get from filtrate or blood filtrate reabsorbing it blood have a gradient only need a transporter for facilitated diffusion can get it into the cell through either source glutamine splits through an enzyme get ammonium ion and bicarbonate facilitated diffusion transporter move bicarbonate out into interstitial fluid then into plasma NH4 needs to get out through counter transport with sodium can t just diffuse out want to get all of it out because it is toxic IV Digestive System Mouth pharynx esophagus through thoracic cavity passes through diaphragm stomach through sphincter muscle called pyloric sphincter separates stomach from small intestine duodenum first portion of SI large intestine colon rectum down to anus Pyloric sphincter multiunit smooth muscle valve between stomach and small intestine Duodenum first part of small intestine receives secretions from liver and pancreas which also secret into blood Major Processes of GI Tract movement two major types peristalsis rhythmic coordinate movement that moves material along the length of the GI tract creates a wave of contraction pretty much goes on all the time but we can increase the rate bolus massive food material being pushed mixing movement present in stomach and intestines move things back and forth helps break material down into small pieces help mix food with any secretions coming in these movements are under control in stomach churning