lecture 6

Question 1

sodium

Answer 1

most prevalent and important solute in ECF

Question 2

effect of high Na+

Answer 2

retain more water so weight increases

Question 3

high Na+ intake in diet

Answer 3

increased osmolarity (body won’t allow), so increased ECF volume, (increased water reabsorption) increasing blood volume and pressure

Question 4

where is Na+ reabsorbed

Answer 4

65% proximal (to aid in reabsorbing other nutrients), 25% thick ascending loop of Henle (create hyper-osmolar fluid), 8% distal, 2% collecting

Question 5

if high GFR

Answer 5

increase Na reabsorption as more fluid in; if low, lower Na reabsorption; always reabsorbing same proportion

Question 6

change amount of Na excreted

Answer 6

change amount put in tubular system (by chaning pressure and GFR)

Question 7

if low BP

Answer 7

increased sympathetic activity (also stimulates granular cells for renin so ang II to reduce BP and Na+ uptake in PCT) and reduced GFR; PCT reabsorb more Na+; sympathetic causes aldosterone release increasing Na+ uptake in distal and collecting duct; if low tubular Na+ at juxtaglomerular apparatus, renin produced

Question 8

if high BP

Answer 8

atrial naturietic peptide, suppresses activity so decreases Na reabsorption

Question 9

JGA of kidney

Answer 9

produces renin due to Na+/K+/Cl- channel. amount of Na+ in goes down, so low osmolarity vs environment so water leaves cells, shrinking them and they produce NO and PGE2 - stimulate granular cells to secrete renin

Question 10

RAAS

Answer 10

liver - angiotensinogen - angiotensin I (renin) - angiotensin II (ACE in lung - greater epithelial SA; causes vasoconstriction) - aldosterone (adrenal) - feeds back to kidney for Na+ and water reabsorption

Question 11

effects of ang II

Answer 11

proximal: increase Na+ and water reabsorption, increasing ECF and BP; vascular: vasoconstriction and increased BP; causes aldosterone synthesis

Question 12

aldosterone

Answer 12

works on principal cells of collecting duct, stimulares Na+ absorption, K+ and H+ secretion; excess causes hypokalaemic alkalosis

Question 13

how does aldosterone work

Answer 13

induces expression of apical Na channel of collecting duct; induces formation of Na+/K+ ATPase pumps by increasing transcription of corresponding mRNA; Na+ reabsorbed into blood and K+ secreted

Question 14

hypoaldosteronism

Answer 14

reduced Na reabsorption in distal, increasing urinary Na loss; ECF volume falls, increasing renin angII and ADH; causes dizziness, low BP, salt craving and palpitations

Question 15

hyperaldosteronism

Answer 15

increased Na reabsorption in distal, decreasing urinary Na loss; ECF volume rises (high BP), reduced renin angII and ADH; increased ANP and BNP; causes high BP, muscle weakness, polyuria, thirst

Question 16

Liddle’s syndrome

Answer 16

inherited hypertension as mutation in aldosterone activated Na+ channel (always on), causing Na+ retention and hypertension

Question 17

reabsorbing water when high Na+, causing polyuria and polydypsia

Answer 17

thirst as higher osmolarity than should have; as more water in, more urine out

Question 18

baroreceptors

Answer 18

low pressure side: heart (atria, right ventricle), high pressure side: vascular (carotid sinus, aortic arch, JGA)

Question 19

low pressure side

Answer 19

can respond to low or high BP; if lowm afferent to brainstem for sympathetic activity and ADH release; if high pressure, atrial stretch so ANP, BNP released

Question 20

high pressure side

Answer 20

slide 29

Question 21

atrial natriuretic peptide (ANP)

Answer 21

small made in atria (also make BNP); released in response to atrial stretch

Question 22

actions of ANP

Answer 22

slide 30

Question 23

slide 31: high GFR

Answer 23

decent diagram

Question 24

slide 32: low GFR

Answer 24

another cracking diagram

Question 25

ACE inhibitors

Answer 25

reduce ang II so reduces vasoconstriction and aldosterone production (less Na+ reabsorption in DCT)

Question 26

osmotic diuretics

Answer 26

glucose (increases osmolarity in tubular fluid, acting as osmotic component so lesser osmotic gradient - diabetes mellitus), mannitol

Question 27

need to ensure more solute gets to dct and collecting duct if high BP to get rid of more water

Answer 27

loop, thiazides, K+ sparing (don’t lose as much K+) - slide 36

Question 28

carbonic anhydrase inhibitors

Answer 28

export H+ at expense of Na+, so if inhibit production of H+ in PCT, so less Na+ can come in, so more Na+ excreted as reaches dct

Question 29

loop diuretics e.g. furosemide

Answer 29

potent; block triple transporter (Na+/K+/Cl-) in ascending limb of loop of Henle; more Na+ in tubular fluid so less in interstitial space also

Question 30

thiazides

Answer 30

block Na+/Cl- symporter in dct

Question 31

K+ sparing diuretics

Answer 31

distal ct; reduce Na+ in from lumen so reduce amount of Na+ pumped out into blood

Question 32

spiralmalactone (inhibits aldosterone)

Answer 32

inhibits Na+/K+ ATPase to blood and Na+ channel in dct (similar to K+ sparing diuretic)

Question 33

high K+

Answer 33

depolarises membranes - action potentials, heart arrhythmias; low also causes heart arrhythmias

Question 34

meal

Answer 34

increase K+ absorption, increase plasma K+, increased tissue uptake quickly (na/k pump) so K+ doesnt rise (stimulated by insulin; reduced by aldosterone and adrenaline)

Question 35

K+ absorption

Answer 35

30% reaches descending loop of henle; anywhere between 1-80% secreted

Question 36

k+ secretion

Answer 36

stimulated by high plasma K+, pH, high aldosterone, high tubular flow rate

Question 37

K+ secetion by principal cells

Answer 37

slide 45

Question 38

aldosterone stimulates K+ into cell and out into lumen

Answer 38

slide 46

Question 39

collecting tube cells

Answer 39

cilia so as flow increase, stimulate PDK1 activity, cascade so increases IC Ca2+ - activates K+ channels to release more K+

Question 40

hypokalaemia

Answer 40

common; diuretics (increases tubular flow rates and K+ excretion), surreptitious vomiting, diarrhoea, genetic mutations (reduced Na+ inport so increased flow rate)

Question 41

hyperkalaemia

Answer 41

response to K+ sparing diuretics, ACE inhibitors; elderly