renal - lecture 3

Question 1

what is clearance of glucose

Answer 1

ZEROOO

Question 2

describe total body balance of sodium and water

Answer 2

na and water are important components of body fluids
total body balance of na and water has to be maintained to sustain normal blood pressure and life
cannot live without water = few days, sodium = few weeks

Question 3

describe water - intake and output

Answer 3

in take = liquids, food, metabolically produced
output = insensible loss, sweat, feces, urine = only thing you can control

subtract metabolic from insensible = both do not feel
~2.5 l balance

Question 4

describe sodium chloride - intake and output

Answer 4

intake = food 10.5g
output = sweat, feces, urine - can control urine

Question 5

what are we in

Answer 5

water intake = water output
sodium intake = sodium output
depends on intake = water output can vary from 0.4l/day-25l/day = if drink hella water, salt output can vary from 0.05g/day-25g/day

Question 6

describe basic renal processes for sodium and water - where

Answer 6

both na and water freely filtered but 99% reabs - no secretion = only filtration/reabs
majority of sodium and water reabsorption ~2/3rds occurs in proximal tubule
major hormonal control of reabs in dct and cd

Question 7

how is sodium reabsorbed

Answer 7

active process occurring in all tubular segments = except descending thin limb of loop of henle

Question 8

how is water reabsorbed

Answer 8

by diffusion = depends on sodium reabs

Question 9

describe active sodium reabs = on basolateral membrane side

Answer 9

active nak atpase pump transports sodium out of cells and keeps intracellular concentration of sodium low

Question 10

describe active sodium reabs = on apical luminal membrane side

Answer 10

sodium moves downhill from tubular lumen into tubular epithelial cells
each tubular segment has diff mechanisms
in proximal tubule = many transport proteins involved, na+-h+ antiporter, counter transport or na+-glucose cotransporter
in ccd = diffusion via na channel

Question 11

describe active sodium reabsorption in ccd - figure

Answer 11

hormonally controlled
nak atpse pump = potassium in and sodium out, sodium reabs triggered by atpase
sodium channels in tubualr lumen = needs concentration gradient generated by atpase pump and moves sodium in
potassium channel = secretion needs gradient and moved out towards tubular lumen

Question 12

describe renal sodium regulation

Answer 12

is increase sodium intake = urinary sodium excretion increases
if decrease sodium intake = urinary sodium excretion decreaes
look bloated when eat salty foods
we are in sodium balance = keep total body sodium constant

Question 13

where does sodium reside in body and explains

Answer 13

major extracellular solute = changes in total body sodium result in similar changes in extracellular fluid volume
total body water = 60% body weight = 40% intracellular and 20% extracellular (3/4 interstitial fluid = 15% and 1/4 plasma = 5%)
Plasma sodium = proportional to amount of sodium

Question 14

what is total body sodium sensed as

Answer 14

intravascular filling by baroreceptors in cardiovascular system
if underfilled = think body has low sodium

Question 15

is plasma concentration of sodium a marker for total body sodium

Answer 15

nooooo
Pna only reflects relative relationship of total body na and water = amount of na/amount of h20

Question 16

what is sodium excreted equal to

Answer 16

sodium excreted = sodium filtered - sodium reabsorbed
sodium not secreted in the tubules

Question 17

how is sodium excretion regulated by - 2

Answer 17

gfr - minor role
sodium reabsorption = most important

Question 18

describe sodium regulation control by gfr

Answer 18

increase na and h20 loss due to diarrhea = decrease plasma vol and venous pressure = decreases venous return AND reflexes mediated by venous arterial and atrial baroreceptors directly increase activity of renal sympathetic nerves
decreased venous pressure = decrease of ventricular end diastolic vol, stroke vol, co and aterial bp = sensed by baroceptors in aortic arch/carotid bodies - also increases activity of renal sympathethic nerves and has direct effect on net gf pressure decreasing gfr
increased activity of renal sympathethic nerves (sensor at level of kidney) increases cosntriction of afferent arteriole and decreased net gf pressure and so decreased gfr and decreased na and h20 excreted

Question 19

describe sodium regulation - control by reabs

Answer 19

key hormone = aldosterone
steroid hormone made and secreted by adrenal cortex, zona glomerulosa
aldosterone stimulates sodium reabsorption in dct and ccd - hormone sensitive

Question 20

what happens when no aldosterone vs high aldosterone

Answer 20

no aldosterone = ~2% of filtered load is excreted - equivalent to 35g of sodium chloride
high aldosterone = ~0% of filtered load excreted

Question 21

describe na reabsorption - anatomically

Answer 21

2/3rds in pt
very little in dt and ccd but this is where hormone control is
amount excreted depends on aldosterone

Question 22

describe effect of aldosterone

Answer 22

affects nak atpse pump
also increases h+ secretion
upreagulate expression
acts on potassium and sodium channels

Question 23

what happens iof tumour on adrenal

Answer 23

primary aldo
high bp since much sodium and low potassium = since k+ secretion activated and low h+

Question 24

describe regulation of aldosterone secretion

Answer 24

raas
renin secreted by kidneys acts on angiotensinogen to convert it to angiotensin 1 - renin responds to vascular filling
angiotension 1 –> angiotensin 2 by ace
and this stimulates adrenal cortex to secrete aldosterone
also stimulates by increased plasma k and acth
inhibited by anp

Question 25

what is renin secreted from

Answer 25

juxtaglomerular cells

Question 26

name 3 ways renin secretion is simulated

Answer 26

sympathetic nerve fiber = constrict afferent arteriole and also stimulates renin secretion
macula densa cells = differentiated columnar tubular cells = detetcs signal and sends to renin secreting cells
afferent arteruole = vascular tension, if bp goes down = tension goes down

Question 27

describe regulation of renin secretion by extracellular fluid volume

Answer 27

decreased plasma vol =
increase activity of renal sympathetic nerve, decrease arterial pressure - direct effect - less of stretch, decrease gfr = decreased flow to macula densa = decrease nacl delivery to macula densa
so renal juxtaglomerular cells increase renin secretion
= increases plasma renin, plasma angiotension 2, and stimulates aldosterone from adrenal cortex and stimulates increased sodium reabs at ccd = decreased sodium excretion

Question 28

what does aldosterone not do

Answer 28

does not stimulate h2o reabs directly in ccd
* diff mechanisms

Question 29

what is anp

Answer 29

atrial natriuretic peptide
anp= peptide hormone secreted by cells in cardiac atria

Question 30

describe what anp does

Answer 30

acts on tubules to inhibit sodium reabs - opp of aldosterone and increases gfr
increased total body sodium - increased extracellular fluid/plasma vol = stimules anp secretion which inhibits

Question 31

what does increased bp do

Answer 31

increases sodium excretion = pressure natriuresis = only if extremely high bp 220 systolic

Question 32

describe action of anp

Answer 32

increase plasma vol = increase distension and anp secretion in cardiac atria= increase plasma anp = decreases plasma aldosterone and BOTH acts on kidneys = arterioles - afferent dilation and efferent constriction –> increase gfr and decease na reabs at tubules distal part = increase sodium excretion = natriuresis