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Renal System Class Notes Clear and concise notes taken during lecture for the renal system. (Received an A)

4 Pages

Kinesiology & Health Science
Course Code
KINE 3012
Tara Haas

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Renal System  The kidneys are responsible for: 1. Fluid and ion homeostasis 2. Waste excretion 3. Drug removal 4. Hormone production 5. Glucose synthesis  20% of blood flow goes into the kidneys  Remember the two structures: cortex and medulla  The nephron is the functional unit of the kidney  The capillary is referred to as the endothelium whereas the tubules are epithelium in the kidney Cortical and Juxtamedullary Nephrons  Cortical nephrons are located in the outer 2/3 of the cortex  Juxtamedullary nephrons are located in the inner 1/3 of the cortex o Characterized by a long loop of Henle which reaches into the medulla o Able to produce more concentrated urine o The peritubular capillaries associated with these nephrons are termed the vasa recta Glomerulus  Podocytes are located along the wall of the glomerulus which have villi-like structures that increase surface area  Glomerular filtration rate (GFR) depends on mean arterial pressure—if there is an increase in MAP, GFR will increase o If there is efferent vasoconstriction, GFR will increase as well Juxtaglomerular Apparatus (Negative Feedback)  If there is an increase in tubule flow (GFR) macula densa secretion occurs which cause afferent arteriole vasoconstriction to decrease GFR Reabsorption  Water, Na+, Glucose  The amount of glucose entering the filtrate is proportional to plasma concentration o Under normal circumstances, there are enough glucose transporters to allow glucose reabsorption…however if there is too much glucose (as in hyperglycemia from diabetes) not all the glucose can be reabsorbed  Vasa Recta surrounds the Loop of Henle and removes H 2 from the medullary interstitium  ADH=vasopressin Vasopressin  Produced by hypothalamus o Release is stimulated by osmoreceptors  Increases water absorption in the collecting duct  Alcohol interferes with secretion  Also acts as a vasoconstrictor (increase blood pressure)  Is the ONLY hormone that increases water retention directly (ie without increasing reabsorption of salt) Other Methods of Controlling Urinary Excretion  Modify glo+erular filtration  Modify Na reabsorption  Aldosterone and Angiotensin II decreases excretion  Atrial natriuretic peptide (ANP) increases excretion Atrial Natriuretic Peptide  Effects both the afferent and efferent arterioles (afferent dilate, efferent constrict) o Increases GFR Aldosterone and Angiotensin II  Angiotensinogen is produced in the liver (inactive precursor to angiotensin) o Renin is an enzyme produced in the kidney that cleaves this peptide into angiotensin I o This is then converted into angiotensin II [by angiotensin converting enzyme (ACE)]  Angiotensin II acts on the adrenal cortex to produce aldosterone o High plasma potassium levels also prompt aldosterone production  Renin is the crucial rate limiting step of this process  Aldosterone initiates transcription for the production of new protein channels (K and Na ) o Increases secretion of potassium and also increased sodium reabsorption o Water follows sodium therefore water ret+ntion increases as well +  If you have overproduction of a
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