Urinary System BIOL 2510 - 001
Popular in Human Anatomy & Physiology II
Popular in Anatomy
This 5 page Study Guide was uploaded by Brooke Polinsky on Saturday April 30, 2016. The Study Guide belongs to BIOL 2510 - 001 at Auburn University taught by Dr. Shobnom Ferdous in Spring 2016. Since its upload, it has received 46 views. For similar materials see Human Anatomy & Physiology II in Anatomy at Auburn University.
Reviews for Urinary System
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/30/16
Urinary System Final Exam Notes: • What are the three steps of urine formation? ◦ ﬁltration,secretion,absorption • What is reabsorption? ◦ the movement of substances from ﬁltration the nephron tubule back into blood via peritubular capillaries/ vasa recta • What would happen if reabsorption didn't occur? ◦ much of substances (99%) ﬁltered will be reabsorption and if this didn't occur we would excrete our plasma volume in less than half an hour • What two processes does reabsorption involve? ◦ passive and active transport • Where does reabsorption occur? ◦ occurs at PCT,LOH,DCT,CD,although most reabsorption occurs in the PCT • What is reabsorbed in the PCT? ◦ all glucose and amino acids: Apical- co-transport,Basolateral- facilitated diffusion ◦ 65% of water: Apical-osmosis via aquaporin,Basolateral- osmosis via aquaporin ◦ 65% of Na+: Apical- Co-transport/Facilitated Diffusion,Basolateral- Na+/K+ATPase (1active transport) ◦ 80% HCO3: reabsorption dependent on H+ secretion ◦ 60% Cl and 55% K+: paracellular route- movement between tubule cells due to leaky tight junctions • What is tubular reabsorption? ◦ quickly reclaims most of the tubular contents and returns them to blood • What is the selective transepithelial process? ◦ almost all organic nutrients are reabsorbed ◦ water and ion reabsorption is hormonally regulated and adjusted • What two processes are involved in tubular reabsorption? ◦ active and passive tubular reabsorption • What two routes can substances follow in tubular reabsorption? ◦ transcellular and paracellular route • What is the transcellular route? ◦ solute enters apical membrane of tubule cells ◦ travels through cytosol of tubule cells ◦ exits basolateral membrane of tubule cells (often involves the lateral intercellular spaces because membrane transporters transport ions into these spaces) ◦ enters blood through endothelium of peritubular capillaries by movement of interstitial ﬂuid • What is the paracellular route? ◦ between tubule cells ◦ limited by tight junctions,but leaky in proximal convoluted tubule nephron ‣ water,Ca2+,Mg2+,K+,and some Na+ in the PCT move via this route ◦ movement through the interstitial ﬂuid and into the capillary • What is the tubular reabsorption of Na across the basolateral membrane? ◦ Na+ is most abundant cation in ﬁltrate ◦ transport of Na+ across basolateral membrane of tubule cells is via primary active transport ◦ Na+-K+ATPase pumps Na+ into interstitial space ◦ Na is then swept by the bulk ﬂow into peritubular capillaries • What is the tubular reabsorption of Na across apical membrane? ◦ Na+ enters tubule cell at apical surface via secondary active transport (cotransport) or via facilitated diffusion through channels ‣ Active pumping of Na+ at basolateral membrane results in strong electrochemical gradient within tubule cell • results in low intracellular Na+ levels that facilitates Na+ diffusion • K+ leaks out of cell into interstitial ﬂuid,leaving a net negative charge inside the cell, which also acts to pull Na+ inward • What does primary active transport provide for Na+ reabsorption? ◦ provides energy and means of reabsorbing almost every other substance • What is active secondary transport? ◦ electrochemical gradient created by pumps at basolateral surface give "push" needed for transport of other solutes ◦ organic nutrients reabsorbed secondary active transport are cotransported with Na+ ‣ glucose,amino acids,some ions,vitamins • What is passive tubular reabsorption of water? ◦ movement of Na+ and other solutes creates osmotic gradient for water ◦ water is reabsorbed by osmosis,aided by water-ﬁlled pores called aquaporins • What are the two types of reabsorption in aquaporins? ◦ obligatory water reabsorption= aquaporins are always present in PCT ◦ facultative water reabsorption= aquaporins are inserted in collecting ducts only ifADH is present • What is passive tubular reabsorption of solutes? ◦ solute concentration in ﬁltrate increases as water is reabsorbed ‣ creates concentration gradients for solutes,which drive their entry into tubule cell and peritubular capillaries ◦ fat-soluble substances,some ions,and urea will follow water into peritubular capillaries down their concentration gradients ‣ for this reason,lipid-soluble drugs and environmental pollutants are reabsorbed even though it is not desirable • Why is sugar in the urine a symptom of diabetes mellitus? ◦ type 1= body produces little to no insulin ◦ type 2= cells do not respond properly to insulin • What is transport maximum? ◦ limits reabsorption ◦ reabsorption of all substances reabsorbed via transport protein is limited by the number of transport proteins present ◦ if plasma levels of substance exceedsTm,it will be excreted ◦ exists for almost every reabsorbed substance ◦ transport rate at saturation • What is the renal threshold? ◦ plasma concentration at which saturation occurs • Loop of Henle reabsorption includes: ◦ Na+,Cl-,K+:but only from ascending limbs ◦ Water:only from descending limbs • What does DCT and CD reabsorption include? ◦ hormonal control ofADH,adolsterone,ANP ◦ Na+: ‣ increase in adolsterone-->increase Na+ reabsorption (and K+ secretion) ‣ increase inANP-->inhibit Na+ reabsorption at CD,(so decrease BV and BP) ‣ water (increase inADH-->increase in water reabsorption) at CD • What are proximal convoluted tubules? ◦ site of most reabsorption ◦ all nutrients such as glucose and amino acids are reabsorbed ◦ 65% of Na+ and water reabsorbed ◦ many ions ◦ almost all uric acid ◦ about half of urea (later secreted back into ﬁltrate) • What happens in the nephron loop? ◦ descending limb:water can leave,solutes can't ◦ ascending limb:water can't leave,solutes can ‣ thin segment is passive to Na+ movement ‣ thick segment has Na+-K+-2Cl symporters and Na+-H antiporters that transport Na+ into cell • some Na+ can pass into cell by paracellular route in this area of limb • Transcellular transport systems are..... ◦ very speciﬁc and limited • What does the transport maximum reﬂect? ◦ number of carriers in renal tubules that are available ◦ when carriers for a solute are saturated,excess is excreted in urine • What is an example of transport maximum? ◦ hyperglycemia leads to high blood glucose levels that exceedTm,and glucose spills over into urine • Where is the DCT and CD hormonally regulated? ◦ ADH and adolsterone • What isADH? ◦ released by posterior pituitary gland ◦ causes principal cells of CD to insert aquaporins in apical membranes,increasing water reabsorption ◦ increased ADH levels cause an increase in water reabsorption • What is aldosterone? ◦ targets CD (principal cells) and distal DCT ◦ promotes synthesis of apical Na+ and K+ channels,and basolateral Na+-K+ATPase for Na+ reabsorption (water follows) ◦ as a result,little Na+ leaves the body ◦ without aldosterone,daily loss of ﬁltered Na+ would be 2%,which is incompatible with life ◦ increase blood pressure and decrease K+ levels • What is an atrial natriuretic peptide? ◦ reduces blood Na+,resulting in decreased blood volume and pressure ◦ released by cardiac atrial cells if blood volume or pressure elevated • What is the parathyroid hormone? ◦ acts on DCT to increase Ca+ reabsorption • What is the release ofADH caused by? ◦ high blood osmolality ◦ high plasma (Na+) ◦ low systemic BP • What causes the release of aldosterone? ◦ low systemic BP ◦ low plasma (Na+) ◦ High plasma (K+) • What are diuretics? ◦ chemicals that enhance urinary output ◦ ADH inhibitors= alcohol ◦ Na+ reabsorption inhibitors = caffeine or drugs for hypertension or edema ◦ Loop diuretics inhibit medullary gradient formation • What are osmotic diuretics? ◦ substance not reabsorbed,so water remains in urine;for example,in a diabetic patient,high glucose concentration pulls water from body • What is secretion? ◦ movement of substances from blood in peritubular capillaries to nephron tubule ◦ disposes of waste in peritubular capillaries ◦ eliminates substances that were passively reabsorbed but not needed by body • What are important secretions? ◦ K+(DCT,CD) ‣ aldosterone increases K+ secretion ‣ coupled with reabsorption of Na+ via Na/K pump ◦ H+ (PCT,CD) ‣ is blood too acidic,increase in H+ secretion ‣ if blood is too basic,decrease in H+ secretion • What are four abnormalities in acid-base balance? ◦ respiratory acidosis- high blood PCO2,due to hypoventilation ◦ respiratory alkalosis- low blood PCO2,due to hyperventilation ◦ metabolic acidosis- low blood pH and HCO3 ‣ cause= consuming too much alcohol,loss of HCO3 due to diarrhea,lactic-acid build up ◦ metabolic alkalosis- high blood pH and HCO3 ‣ cause= vomitting,consuming excess base in food (taking too many antacids) • What is an important function of the kidneys? ◦ maintain water and ion balance in body ﬂuids • What is osmolality? ◦ number of solute particles per kg of water ◦ units are milliosmol/kg (mOsm) ◦ blood plasma= 300 mOsm • What are concurrent mechanisms? ◦ ﬂuid ﬂows in opposite directions through adjacent segments of the same tube ◦ work together to maintain and establish medullary osmotic gradient from renal cortex through medulla ◦ ascending/descnding loop of henle and vasa recta ◦ gradient runs from 300 mOsm in cortex to to 1200 mOsm at bottom of medulla • What does the kidney due in response to dehydration and over hydration? ◦ dehydration= produce small amounts of urine ◦ over hydration= produce dilute urine ◦ accomplish this through countercurrent mechanism • What are the two types of counter current mechanisms? ◦ countercurrent multiplier= interaction ﬁltrate ﬂow in ascending/descending limbs of nephron loops of juxtamedullary nephrons ‣ creates gradient ◦ countercurrent exchange= blood ﬂow into ascending/descending limbs of vasa recta ‣ preserves gradient • Countercurrent Multiplier depends on? ◦ ﬁltrate ﬂow in opposite directions (ascending/descending) ◦ difference in permeabilities between descending nephron loop and ascending loop ◦ active transport of solutes out of ascending limb ◦ limbs of nephron loop are not in direct contact but are close enough to inﬂuence each other's exchanges with surrounding interstitial ﬂuid • How does LOH establish medullary osmotic gradient? ◦ 1.ﬁltrate entering LOH isometric blood plasma and interstitial ﬂuid ◦ 2.Along descending limb,H2O passes out of ﬁltrate by osmosis ‣ ﬁltrate becomes more concentrated ◦ 3.along ascending limb,NaCl leaves ﬁltrate ‣ NaCl contribute to osmolality of interstitial ﬂuid ‣ ﬁltrate becomes more dilute • How does the vasa recta maintain gradient and take up reabsorbed water? ◦ 1.blood ﬂowing deeper into medulla becomes more concentrated ◦ 2.blood ﬂowing towards cortex picks up H2O and loses salt • How is urine concentrated? ◦ action ofADH on collecting duct ◦ osmoreceptor in hypothalamus detect changes in osmolality of extracellular ﬂuid ◦ even slight changes in osmolality activates osmoreceptors and changes ADH release from pituitary • What happens in the body when someone is over hydrated? ◦ decreases blood ECF osmolality ◦ lowersADH secretion from posterior pituitary ◦ lowers number of aquaporins in CD ◦ decrease H2O reabsoprtion from CD ◦ dilute urine produced ( and decreases blood volume) • What happens in the body if your dehydrated? ◦ increase osmolality of extracellular ﬂuid ◦ increaseADH release from posterior pituitary ◦ increase number of aquaporins in CD ◦ more H2O reabsorption from CD ◦ concentration urine produced and increases blood volume • How does the movement urea helps to concentrate urine? ◦ urea is a nitrogenous waste product but can enter ascending limb by diffusion ◦ ADH increase urea diffusion out of CD,which then enters ascending LOH to make ﬁltrate entering CD even more concentrated (more H2O absorbed) • Why is frequent urination a symptom of diabetes insipidus? ◦ caused by lack ofADH orADH receptors in CD
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'