Renal Physiology Flashcards

Question

GFR changesbasedonneuralandhormonalinputto theefferentandafferentarterioles

Answer 1

o Constriction of afferent arterioles reduces blood flow in and, therefore, reduces GFR o Constriction of efferent arterioles reduces blood flow out and, therefore increases GFR

Answer 2

-substances are re absorbed within the renal system o 180L of water is filtered per day and 99% of it is reabsorbed o 180g of glucose is filtered per day, with 100% reabsorbed (in a healthy person) o For some substances, such as water, the %reabsorption is under physiological control

Answer 3

Urea is reabsorbed via diffusion, allowing it to move freely across membranes, resulting in a concentration in filtrate that is the same as plasma. As filtrate moves through the proximal tubule, water is reabsorbed so the concentration of urea in the tubule increases... As the concentration in tubule is now greater than that in the peritubular capillaries, urea is reabsorbed by diffusion Thus, urea reabsorption is determined by water reabsorption

Answer 4

-involves the use of channels or transporters to move substances across membranes -many substances are actively transported with sodium.Sodium moves across a membrane via a transporter from an area of high to low concentration.At the same time, another molecule (i.e., amino acids, glucose) moves from an area of low to high concentration (against the concentration gradient) using the same transporter

Answer 5

-similar to diffusion -Combines Mediated transport and diffusion although direction is different... I.e. from peritubular capillaries into tubular lumen. -managed substances include hydrogen ions and potassium ions as well as foreign chemicals

Answer 6

= mass of substance excreted per unit time / plasma concentration of substance Forexample:Urine mass (urine concentration of substance *urine volume) / plasma concentration of substance

Answer 7

Sodium is the main ion found in extracellular fluid o Normally between 135 and 145 mmol/L o Sodium Balance is achieved when sodium intake is the same as sodium loss o Sodium intake is in the form of food and drink (about 8.5g per day) o Sodium loss is in the form of sweat, urine and loss via faeces (in total about 8.5g per day)

Answer 8

Watermakesupbetween55and75%ofbodymass o Relatively small deviations can be problematic (i.e., Hypo or hyper-hydration) o Water balance is achieved when water intake is the same as water loss o Water intake=drinking,foodandmetabolicproduction(about3L perday) o Water output=sweat,urine,breathing,skinloss,lossinfaeces(intotalabout3L perday) o If water intake is increased, in normal situations water balance is ensured by an increase in urine production

Answer 9

1)filtration by glomerous 2)obligatory absorption and secretion by proximal tubule 3)generation of osmotic gradient by loop of henle 4)regular red absorption and secretion by distal tubule 5)regulated by water uptake by collecting ducts

Answer 10

-anti-diuretic hormone (ADH) o Diuretic =substance that increases urine production o Released from the anterior pituitary gland primarily as a result of an increase in plasma osmolality... ...A reduction in plasma osmolality leads to reduced secretion of AVP -Results in the insertion(reabsorption of water and the production of low volumes of concentrated urine )or removal of aquaporins from the collecting ducts

Answer 11

o Filtrate in tubule follows a counter-current arrangement... i.e., Flows down the descending limb and up the ascending limb o Sodium is actively transported out of the thick ascending limb o The proximal tubule and the descending limb allow free movement of water and passive movement of sodium o The ascending limb, the distal tubule and the collecting ducts are relatively impermeable to sodium o The ascending limb and the first section of the distal tubule are impermeable to water

Answer 12

-Fluid filtered by the Glomerulus passes through the proximal tubule and enters the loop of Henle with an osmolarity of 300 mOsm/l -Osmolarity changes as urine flows down the tubules -formation of hypertonic urine is due to presence of ADH

Answer 13

Urinary loss of sodium is determined by the absorption or secretion of sodium within the nephron o Remember, the proximal tubule and descending limb of loop of Henle allow passive movement of sodium - this happens anyway,regardless of sodium levels in blood o The majority of regulation of sodium absorption or secretion into urine occurs in the distal tubule and the collecting ducts... o Reabsorption is achieved through active transport that involves co-movement of potassium o Recall from previous section that the ascending limb of loop of Henle passes between the afferent and efferent arteriole supplying the glomerulus Macula Densa + specialised cells in afferent arteriole = juxtaglomerular apparatus (JPA) -When sodium of filtrate within distal tubule is low, juxtaglomerular cells secrete renin...

Answer 14

-Renin converts a protein called angiotensinogen to angiotensin1 which is then converted to angiotensin 2 -Occurs in the presence of angiotensin converting enzyme (ACE) -Angiotensin 2 acts on the adrenal gland which leads to the release of aldosterone, subsequently this leads to an increase in the number of sodium channels which are inserted into the collecting ducts... More reabsorption of sodium (and water)... Ultimately, when blood sodium increases, plasma volume increases (this also increases blood pressure!) • Counteracted by Atrial Natriuretic Peptide

Answer 15

-LOW SODIUM IN FILTRATE - DETECTED BY JGA -SECRETION OF RENIN INTO THE BLOOD -ANGIOTENSINOGEN TO ANGIOTENSIN1 -ANGIOTENSIN 1 INTO ANGIOTENSIN 2 -ALDOSTERONE -SODIUM REABSORPTION

Answer 16

-Hormone released from cells in the right atria (think close relationship with BP)... o Key determinant of release is stretch of the right atria or ‘End Diastolic Pressure’.. -Release of it leads to o Increased sodium secretion at collecting ducts o Reduced action of angiotensin 2 o Inhibition of renin secretion o Increases glomerular filtration rate