BIOL 252 1st Edition Lecture 22 Outline of Last Lecture I How significant is pulmonary elasticity II Ventilation III Resistance to Airflow IV Respiratory Volumes V Restrictive Pulmonary Disorders VI Obstructive Pulmonary Disorders VII Gas exchange VIII Gas transport IX Urinary System X Kidney Function XI Nitrogenous Wastes XII Nephron Outline of Current Lecture I Steps in Urine Formation II Renal Corpuscle III Regulation of Glomerular Filtration IV Proximal Convoluted Tubule Tubular reabsorption Current Lecture I II Steps in Urine Formation a Glomerular filtration creates plasmalike filtrate of blood b Tubular reabsorption removes useful solutes from filtrate returns them to blood i Tubular secretion removes additional wastes from blood adds them to filtrate c Water conservation removes water from urine and returns it to blood concentrates wastes Renal Corpuscle a Glomerulus and Bowman s capsule comprise renal corpuscle b Podocytes because they have feet interdigitate with neighbors i Make narrow slit called a filtration slit ii If something goes from capsular space to blood will have to go through filtration slits c Capsular space where filtrate goes 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 III d Physiology i Filtration w out reabsorption ii Blood hydrostatic pressure 60 out pressure w in capillary iii Colloid osmotic pressure 32 in pressure due to high osmolarity of blood due to proteins proteins in blood osmosis water tends to go into capsular space iv Capsular pressure 18 in pressure within the glomerular capsule 1 Due to confined space v NET filtration pressure 10 mm Hg pushing in outward direction pushes fluid through tubule system e Importance of NFP i Determines flow ii Glomerular filtration rate volume of filtrate over time 1 Typical male 180 L day iii How is NFP related to GFR 1 If one goes up the other goes up 2 Proportional iv How can we lower filtration rate 1 Efferent arteriole constriction a 2 Constricting systemic arterioles a Constricting arterioles increases peripheral resistance b Resistance increasing higher BP the same as elevating aortic BP 3 Elevating aortic blood pressure a BHP increases 60 b Increases NFP increases GFP 4 Afferent arteriole constriction a Making it smaller decreases pressure in glomerulus f Importance of GFR i Affects reabsorption and secretion ii If GFR too high reabsorption insufficient iii If GFR too low wastes are reabsorbed Regulation of Glomerular Filtration a Renal Autoregulation i Tubuloglomerular feedback tells filtration apparatus how it should change controls vasoconstriction of afferent arteriole 1 Macula densa controls afferent arteriole diameter 2 If salty filtrate b c left too many things behind slow down filtration rate 3 Salty filtrate slows GFR dilute filtrate increases GFR ii Myogenic mechanism 1 Afferent arteriole responds to pressure and controls its own diameter 2 High arterial BP running etc elevates BP a If arterial pressure goes up by 10 to 70 mm Hg afferent arterioles constrict b Sympathetic control i Under fight or flight afferent arterioles constrict b c of higher arterial blood pressure AND must divert blood to parts of body that need it 1 Divert away from digestive organs and kidneys 2 At the consequence of renal function dramatically decreases NFP c Renin angiotensin aldosterone mechanism i Hormone system ii When BP drops below ability to autoregulate renin released from JG cells iii Angiotensinogen converted to angiotensin I by renin iv Angiotensin I converted to angiotensin II by ACE 1 Angiotensin II a Affects hypothalamus makes brain think we re thirsty i Adding water to blood elevates BP b Vasoconstriction elevated BP i Arterioles constrict increases peripheral resistance increases BP restores filtration c To adrenal cortex i Aldosterone stimulates even more reabsorption pull sodium into blood water in tubules will follow it ii Reabsorb sodium and water retaining as much water as possible iii Increases BP and restores filtration iv Urine is very concentrated more wastes volume of water d Which would NOT result in afferent arteriole vasoconstriction i Severe hemorrhage 1 Hypovolemia low BHP causes us to have afferent arteriole dilation and possibly renin release ii High glomerular hydrostatic pressure 1 High BHP high NFP want to lower it 2 Lower NFP by arteriole constriction iii Elevated angiotensin II 1 Increases BP causes constriction of afferent arteriole iv High osmolarity in DCT 1 GFR is high pushing fluid too quickly 2 Must lower GFR must lower NFP IV 3 Lower NFP by afferent arteriole constriction Proximal Convoluted Tubule Tubular reabsorption a Movement of substances from filtrate to blood occurs via paracellular route b And via transcellular route c Transport maximum i Limit to amount of solute that renal tubules can reabsorb ii If you have diabetes hyperglycemia too much glucose 1 Filter huge amounts of it reach transport maximum 2 All transporters occupied