renal - lecture 3 Flashcards
what is clearance of glucose
ZEROOO
describe total body balance of sodium and water
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
describe water - intake and output
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
describe sodium chloride - intake and output
intake = food 10.5g
output = sweat, feces, urine - can control urine
what are we in
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
describe basic renal processes for sodium and water - where
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
how is sodium reabsorbed
active process occurring in all tubular segments = except descending thin limb of loop of henle
how is water reabsorbed
by diffusion = depends on sodium reabs
describe active sodium reabs = on basolateral membrane side
active nak atpase pump transports sodium out of cells and keeps intracellular concentration of sodium low
describe active sodium reabs = on apical luminal membrane side
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
describe active sodium reabsorption in ccd - figure
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
describe renal sodium regulation
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
where does sodium reside in body and explains
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
what is total body sodium sensed as
intravascular filling by baroreceptors in cardiovascular system
if underfilled = think body has low sodium
is plasma concentration of sodium a marker for total body sodium
nooooo
Pna only reflects relative relationship of total body na and water = amount of na/amount of h20
what is sodium excreted equal to
sodium excreted = sodium filtered - sodium reabsorbed
sodium not secreted in the tubules
how is sodium excretion regulated by - 2
gfr - minor role
sodium reabsorption = most important
describe sodium regulation control by gfr
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
describe sodium regulation - control by reabs
key hormone = aldosterone
steroid hormone made and secreted by adrenal cortex, zona glomerulosa
aldosterone stimulates sodium reabsorption in dct and ccd - hormone sensitive
what happens when no aldosterone vs high aldosterone
no aldosterone = ~2% of filtered load is excreted - equivalent to 35g of sodium chloride
high aldosterone = ~0% of filtered load excreted
describe na reabsorption - anatomically
2/3rds in pt
very little in dt and ccd but this is where hormone control is
amount excreted depends on aldosterone
describe effect of aldosterone
affects nak atpse pump
also increases h+ secretion
upreagulate expression
acts on potassium and sodium channels
what happens iof tumour on adrenal
primary aldo
high bp since much sodium and low potassium = since k+ secretion activated and low h+
describe regulation of aldosterone secretion
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
what is renin secreted from
juxtaglomerular cells
name 3 ways renin secretion is simulated
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
describe regulation of renin secretion by extracellular fluid volume
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
what does aldosterone not do
does not stimulate h2o reabs directly in ccd
* diff mechanisms
what is anp
atrial natriuretic peptide
anp= peptide hormone secreted by cells in cardiac atria
describe what anp does
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
what does increased bp do
increases sodium excretion = pressure natriuresis = only if extremely high bp 220 systolic
describe action of anp
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
