BCMB 230 1st Edition Lecture 22 Outline of Last Lecture I.Urinary SystemII.Structure of NephronIII.Flow PathIV.Types of NephronsV.Glomerulus and Glomerular CapsuleVI.Physiological Processes of the NephronVII.Processes of the KidneyOutline of Current Lecture I.Ion Gradients and Osmotic Pressure in NephronII.Juxtaglomerular ApparatusIII.Regulation of Blood Calcium LevelIV.Regulation of H+ (pH) in PlasmaCurrent LectureI. Ion Gradients and Osmotic Pressure in NephronNa+/K+ ATPase in the proximal convoluted tubule, the ascending loop of Henle, and the distal convoluted tubuleObligatory reabsorption of water occurs in the proximal convoluted tubule and the descending loop of HenleRegulated reabsorption of water occurs in the distal convoluted tubule and the collecting duct-Reabsorption in the distal convoluted tubule is regulated by aldosterone-Reabsorption in the collecting duct is regulated by ADH (controls permeability of membrane)Descending loop of Henle-permeable to waterAscending loop of Henle-never permeable to waterBlood, filtrate, interstitial fluid-all isoosmotic with cytoplasm; all 300 mOsm-osmotic pressureCounter-current exchange system-tubes right next to each other with different flows; a way thatwe can create gradients (ion gradients or temperature gradients)-male reproductive physiology-also uses a counter-current exchange system-testes cannot be body temperature in order to produce sperm-testes outside of body cavity-want to regulate temperature of testes; keep it cooler than body but relatively constantThese 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.-do this with a counter-current exchange system-venous blood is cooler than arterial blood; two vessels cause movement of heart from arteries to veinsCounter-current exchange system-Create ion gradients in interstitial fluid-only works in medulla in kidneyIn juxtamedullary nephron:Cortex is isoosmotic-osmotic pressure=300 mOsmMedulla- -becomes hyperosmotic or hypoosmotic depending on different parts of the nephron-in the interstitial fluid: becomes saltier as we go down; is constant through the whole general regionFiltrate: -in descending loop of Henle-filtrate becomes more concentrated (saltier) as it descends because it is permeable to water and the flow goes down, following the ion gradient of the interstitial fluid; water leaves the filtrate-in ascending loop of Henle-filtrate becomes less concentrated because sodium ions are leaving and water can’t get in because the membrane of the ascending loop of Henle is impermeableIf we keep the impermeability after the ascending loop of Henle, we get a high volume/low concentration of urine-this happens when we have plenty of water-means that there is no ADHIf we make it more permeable after the ascending loop of Henle, we get a low volume/high concentration of urine-this happens when we do not have enough water-means that ADH is presentVasa recta maintains ion gradient; loop of Henle creates ion gradientBy manipulation ADH concentration, can manipulate volume and concentration of urineThe vasa recta only maintains ion gradients that the loop of Henle creates.Aldosterone-acts on sodium potassium ATPase (1:1 relationship)-cause sodium reabsorption-cause potassium secretionIncrease aldosterone-increase sodium reabsorption and increase in potassium secretion at the same timeHigh sodium-do not want aldosteroneLow sodium-do want aldosterone (prevent loss of it)-maintains levels, does not make sodium plasma level increaseHigh potassium-do want aldosterone (cause potassium to be secreted, decrease levels, gets rid of some of it)Low potassium-do not want aldosteroneLow sodium and low potassium-conflicting signals; listen to sodium because it is mostly outside the cell-more subject to filtration (potassium inside the cell); a lot easier to lose sodium through kidney than potassiumII. Juxtaglomerular Apparatus-detect things like pressure and ion concentration-gland that secretes chemical messenger called rennin -renin circulates in the blood and comes in contact with plasma protein from liver called angiotensinogen -angiotensinogen cleaves a piece of angiotensiogen off and creates an active form called Angio tensin I -Angio tensin I circulates in the blood to the lungs where there is an angiotensin converting enzyme called ACE-ACE takes angiotensin I and turns it to angiotensin II which has three major effects: -potent system vasoconstrictor (helps to drive pressure up)-goes to adrenal cortex and causes secretion of aldosterone which acts on distal convoluted tubule make absorption of Na+-stimulates the secretion of ADH-very powerful physiological response if blood pressure is lowCauses of blood pressure going down: blood loss, vasodilation due to shock, cardiac failureHigh blood pressure is more of a problem because we don’t have physiological response well prepared for it-Causes of blood pressure getting high: sedentary, too much food, stressAtrial naturetic peptide-hormone; (naturetic=has to do with sodium); comes from the atrium of the heart; when the heart stretches, the atrial appendage releases this hormone which influences kidney to reduce sodium reabsorption; might help a little bit to bring high blood pressure down-weak response, does not work very wellIII. Regulation of Blood Calcium Level-drop in plasma calcium-cause secretion of hormone called parathyroid hormone coming from the parathyroid gland (little glands in the next buried within the thyroid gland); has target cells in kidney and the bone-in bone-causes resorption-dissolve/break down tissue; break down bone tissue--get release of calcium and plasma calcium levels go up-doing this too much, get structural problems-bones get weak-in kidney-increase calcium reabsorption, decrease urinary excretion of calcium (does not bring calcium levels up, just keeps it from losing calcium); also in kidney, take and activate vitamin D acts on the intestine and increases absorption of calciumIV. Regulation of H+ (pH) in PlasmaAcidosis-pH has dropped, or there has been an increase in hydrogen ionsAlkalosis-increase in pH, decrease in hydrogen ions concentration-can’t have both at the same timeUse a buffer system to help prevent these from ever happening-helps to prevent pH change.Plasma is buffered by a bicarbonate buffer system: H20 + CO2 <-> H2CO3 <-> H+ + HCO3-Adding H+ shifts equation to the left, carbon dioxide