BCMB 230 1st Edition Lecture 22 Outline of Last Lecture I Urinary System II Structure of Nephron III Flow Path IV Types of Nephrons V Glomerulus and Glomerular Capsule VI Physiological Processes of the Nephron VII Processes of the Kidney Outline of Current 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 Current Lecture I Ion Gradients and Osmotic Pressure in Nephron Na K ATPase in the proximal convoluted tubule the ascending loop of Henle and the distal convoluted tubule Obligatory reabsorption of water occurs in the proximal convoluted tubule and the descending loop of Henle Regulated 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 water Ascending loop of Henle never permeable to water Blood filtrate interstitial fluid all isoosmotic with cytoplasm all 300 mOsm osmotic pressure Counter current exchange system tubes right next to each other with different flows a way that we 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 constant 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 do this with a counter current exchange system venous blood is cooler than arterial blood two vessels cause movement of heart from arteries to veins Counter current exchange system Create ion gradients in interstitial fluid only works in medulla in kidney In juxtamedullary nephron Cortex is isoosmotic osmotic pressure 300 mOsm Medulla 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 region Filtrate 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 impermeable If 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 ADH If 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 present Vasa recta maintains ion gradient loop of Henle creates ion gradient By manipulation ADH concentration can manipulate volume and concentration of urine The 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 secretion Increase aldosterone increase sodium reabsorption and increase in potassium secretion at the same time High sodium do not want aldosterone Low sodium do want aldosterone prevent loss of it maintains levels does not make sodium plasma level increase High potassium do want aldosterone cause potassium to be secreted decrease levels gets rid of some of it Low potassium do not want aldosterone Low 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 potassium II 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 low Causes of blood pressure going down blood loss vasodilation due to shock cardiac failure High 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 stress Atrial 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 well III 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 calcium IV Regulation of H pH in Plasma Acidosis pH has dropped or there has been an increase in hydrogen ions Alkalosis increase in pH decrease in hydrogen ions concentration can t have both at the same time Use 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 HCO3Adding H shifts equation to the left carbon dioxide can be excreted through breath Not enough H shifts equation to the right