BCMB 230 1st Edition Lecture 23 Outline of Last Lecture I.Ion Gradients and Osmotic Pressure in NephronII.Juxtaglomerular ApparatusIII.Regulation of Blood Calcium LevelIV.Regulation of H+ (pH) in PlasmaOutline of Current Lecture I.Plasma pH RegulationII.Reabsorption and SecretionIII.Bicarbonate Handling-pH in the KidneyIV.Digestive SystemCurrent LectureI. Plasma pH RegulationChange in hydrogen ion concentrationbuffer prevents pH change until buffering capacity is reached, then buffering does not continue to workAcidosis-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 CO2 in the air being breathed in-metabolic-prolonged diarrhea; production of nonvolatile acids through cellular processesAlkalosis-H+ decrease, pH increase-respiratory-hyperventilation; decrease CO2, increase pH-metabolic-prolonged vomiting (loss of H+), utilization of H+ ions in cellular processesMetabolic-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 kidneysIf problem is metabolic, temporary patch is respiratory compensation-problem is metabolic, fix it with the lungsMetabolic 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 CO2Metabolic alkalosis-too little H+-hypoventilate-respiratory compensation-have more CO2Respiratoryrenal compensation for respiratory acidosis-increase bicarbonate reabsorption (by tubular metabolism) in kidney-increase bicarbonate production in kidney-increase secretion of H+ ionsRespiratoryrenal compensation for respiratory alkalosis-response is weak; don’t have a strongphysiological response to thisII. Reabsorption and SecretionFiltrate in tubules, tubular cells, interstitial fluid, peritubular capillary with blood in itTight junctions between cells-help to localize protein on one side versus the other of the membraneEpithelial 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 fluidNa+/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 outReabsorption 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 membraneIII. Bicarbonate Handling-pH in the KidneyLargely 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 enzymeCall 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 metabolismCan 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 toxicIV. Digestive SystemMouth, 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 anusPyloric sphincter-multiunit smooth muscle valve between stomach and small intestineDuodenum-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 lengthof 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