renal and electrolyte balance Flashcards
wher does water input come from?
dietary food and drink
metabolic water, a product of cellular respiration
where does water output come from
urine air in the lungs faeces sweat skin
define osmolarity
total concentration of solutes in the solution of plasma
in plasma it must stay the same even after drinking
what does the kidney do to keep the plasma osmolarity the same after a drink
amount of urine will increasing
it will be more dilute
amount of solutes being excrested is the same and remains constant
what is obligitory resorption
dilutes things
resorbs salts and water follows
uses an osmotic gradient across the medualla
what does obligitory resorption do
uses counter current multiplication
parallel tubes running in opposites directions concentrating the urine
describe facultative resorption
ADH dependent
affects the collecting ducts
how does the osmotic gradient affect obligitory resorpton
active Na/K and cl transportes set a gradient
Na actively out of ascending loop
tight junctions prevent water leaking out
increased osmolarity in ISF
decreased osmolarity in the ascending tubules
less salt in tubules
uses gradient set up
what are the three processes regulating water balance
obligitory:
osmotic gradient
counter current multiplication
facultative hormones
how does counter current multiplication work
the osmotic graident set up using Na pulls water from the descending loop into ascending
concentrates it
where does water move during concentrating in the loop of henle
water leaves the descending llop
but then stuck in the ascending
this concentrates the tubular fluid
describe the steps in counter currrent multiplication to concentrate urine
- tubular fluid osmolarity equal to ISF
- active transport of Na,K,Cl from ascending loop makes gradient
- water moves out of descending by osmosis into ISF untill gradient establised
- fluid enters the system from the top moving it all around
- further active transport of Na,K,Cl ions from ascending incerasing concentration gradient
- further mvoement of water out of descending limb until gradient established
- repeat
what does counter current multiplication result in
more solutes in ISF
creates a smaller volume of concentrated urine
what drives facultative resorption
hormones
ADH is the priciple one
what does aldosterone do
drives the rennin-angiotensin-aldosteron system
regulated electrolyte lvels and salts
affects P cells in dsital and collecting ducts
describe what aldosterol does
triggers Na to be resorbed into P cells
and K to be secreted out inot tubules
water then follows the Na
the amount of K to be lost depends on the amount of aldosterone
what does high aldosterone result in
concentrates urine
what regulated aldosterone secretion
negative feedback
what inhibits aldosterone secretion
high sodium levels
high blood volume
high blood pressure
what does low aldosterone levels do to urine
dilutes it
what is ANp
atrial natiuretic peptide
were does ANp come from
secreted by atria of the heart in response to stretch
large blood voumes cause it
what does ANP do to the kidney
decreases the absorption of sodium and water from proximal convoluted tubules and collecting ducts
causes there to be more dilute urine
what does high ANPcause
inhibted ADH and aldosterone secretion
what does ADH do
altes the collecting ducts permeablity to water and urea
what does ADH cause to happen
pathway to translocate aquaproins to the membrane allowing water back in to blood
what triggers ADH
high osmotic pressure triggers secretion of ADH from pituitary
low ADH=
dilute urine
High ADH
concentrated urine
stages leading to ADH being released
blood osmotic pressure raised sensed by osmoreceptors in hyppthalamun stimulates the pituitary more ADH secreted which leads to increase resorption of water blood osmotic pressure lowered
what is a diuretic
substances that slow renal respotion
causes diuresis
more urine
examples of duiretics
caffine alchol cold weather stress some medicines
how does caffine increase urine
inhibits Na resoprtion
how does alchocol act as as diuretic
inhibits ADH secretion
what does cold weather do to cause more urination
skin vasoconstriction and deep vasodilation
higher BO inhibting ADH secretion
vasodilation of kidney afferent arteriole
increases GFR
what does the sympatetic nervous system do to the kidney
concentrates urine
triggers constriction of:
afferent arteriole to reduce GFR
stimulates rennin production
what does noradrenaline do?
constricts the afferent arteiole to reduce GFR
more rennin
higher angiotensin
increased Na and water resorbption
what is the key salt balancer
aldosterone
where is sodium most common?
ECF cation
where is potassium most common
cation ISF
what does ADH regulate
water
what regulate electrolytes
rennin-angiotensin-aldoserone mechanism
atrial nariuetic peptide
when is rennnin made
in response to low sodium levels
what detects low sodium levels to signal rennin
cells lining thd sital tubule detect the levels and signal nearby granular cells of the afferent artiole to release rennin
what does rennin do?
converts to precursor angiotensin 1
thn to angiotensin 2 using an enzyme called ACE can now act on the adreanal corext to mae aldosteroneq
what is hyperkalaemi
high blood potassium
also signals for aldosterone
what signals to release rennin
low blood volune
low blodo pressure
low sodium
what does aldosterone do to the kidneys
resortion of sodium and water
increased excrestion of potassium
results in higher blood Na levels
higher blood volume and higher BP
what causes rennin to be stopped
higher sodium in the blood
higher blood volume and BP
what ca angiotensis 2 cause?
casoconstriction leading to increased blood pressure negativelt feddbacking the kidnesy to stop secreting rennin
what does ANP cause
decreases resoprtion of sodium and water fromm proximal convoluted tubules nd collecting ducts
makes urine more dilute
where is most of the sdum resorbed
proximal tubule by active transport
distal tubule and collecting duct by aldosterone
what deos a low K diet mean
more is resorbed
wher is pootassium resorbed
proximal convoluted tubule by leaky jucntions
how do diuteitc impact potassium
inhibit water resorbtion by inhibiting the cotransporter
reduced the resorption of K therefore
causes hypokalaemia
what is potassium excess
hyperkalaemia
what is potassium deficiency
hypokalaemia
what are luminal anions
presence of anions in the lumen caues secretion of K to neurtralise the charge
what increased K secretion ( luminal anions)
increased gradient
what factors decrease K secretion ( luminal anions)
decreased gradient
factors affecting potassium levels
aldosterone electrochemica gradent of luminal anions dietary K acid base disturbances diuertics
how does aldosterone impact K
increases the number of K channels in the luminal mmebrane to incrase K secretion by the P cells
what causes hypokalaemia
alkalosis
K moves out of blood inot cells
K deficiency
what cuses hyperkalameia
acidosis
K movesinto blood out of cells
K excess
how do luminal anions affect potassium
presence of large anions such as sulfate in lumen of distal tubule and collecting duct incrase K secretion
define hyponatraemia
low soodium levels
most common
caused by diarrohae, heart failure, hypothyriodism, diuretics
define hypokalaemia
low potassium
can cause muscle weakness and cariac arrythmias
what is hypoovaolaemic hyponatraemia
reduced ECF
what is erythropeotin
Epo
regulates red cell production by the bone marrow
produced by the kidnesy in response to hypoxia
what systems maintain acid base balance
blood bufferin
metabolis system]respiraotry system
renal system
what do acids so when in olution
release H+ ions
what do alkaline do in solution
accept H+ ions in solution
often release OH- which can accetp the H+ to form H2)
what is a buffer?
chemical which can bind revesibly to hdrogen ions
they set the pH
name the mian blood buffers?
protein bufffer system
phosphate buffer system
carbonic acid-biocarbonate system
how doe the protein buffer systm wrok
haemoaglobin accepts and donated hydrogen ions
role of haemalogin in protein buffering
accepts or donates hydrogen ions
prevents large changes in plasma p
how can aminoa acids alo work in protein buffering?
some have basic side chains and accept hydrogen, some have cidic side chains donating electrons
what is phsophate buffering
phosphate fund in bones
it can accetp H+ to mkae dihydrogenphosphate which is used intracellukarly and urinarry as a buffer
what hapens if there is too much freee hydrogen
need more phsphate so its taken out of the bones leading to osteoporosis
how does the bicarbonte buffering syste work
bicarbonate accepts and donates H+ions
used in the ECF
how does bicarboate work as a buffe
bicarbonate accepts H to form carbonic acid
this can then dissociate to carbon iodixde and water
what does high carbon iodxide to to pH
increases Hydrogen and loweres the blood pH
what does low carbon dpxide to do pH
loweres the Hydrogen and raises the pH
what does high bicarbonate cause
mops up the H
reduced the hydrogen leading to a raised pH
what does a ow bicarbonate cause
increase hydrogen and thus a lower pH
what controls acid base homeostasis
3 main body systems –>
metabolic
respiratory
renal
which is the fasted form of acid base balancing
respiratory system and metabolic activity
what is used in the long term to control buffering
renal system
what eliminates hydrogen ions
respirtry exchange
how does metabolic activity form acid?
normal cellular respiration generates CO2
this combines with water to make carbonic acid
this is trasnported to the lungs as bicarbonate and hydrogen
more hydrogen
what dertmines a foods acidity or alkaniity
how t breaks down
eg citrus fruits are acidic by alkaline forming hen brokwn down
how do we remove hyrdrogens through respiatory system
hyperventilate
change the breathing rate to alte the hydrogen concentration and the equibrium
largely subconscious
in condictions of hiogh hydrogen what happens to breaing
hyperventilate
loss off carbon iodixde
lowers hydrogen
how long does renal regulation of pH take?
slow
hours or days
how does the kidne regulate high hydrogen
hgh hydrogen stimulate the kidney to secrete hydrogen
reabsorb bicarbonate where its then recycled
how does the kidney deal with low hydrogen
resorbs hydrogen
secretes bicarbonate and lets go of it
define acodisosi
too much hydrogen in the blood
what does acidocisis cause?
trigers increase breathing rate to remoe carbon dioxide
hydrogen ions are secreted in kidnesy
bicarb is recyced and reabsorbed
define alkalosis
low blood pH
what happens in alakosis
slow breathing
reduced respiration
reduced hydrogen secretion
secretes bicarb instead
how is ph/acid-base balance maintained?
renal secretion of H+ and reabsorption of bicarbonate
what us HCO3
bicarbonate
how is hydrogen removes in urine
active proton pump moves it into the urine making it acidic
but it combines with other things to make it less harsh
how is H+ secreted in the proximal tubules
Na/H+ antiporter
what can hydrogen combie with to be les harh
ammonia to mkae ammonia uions
hydrogen phosphate to make dihydrogen phosphate
both are excreted
how much of they hydrogen made y the body is excerted?
all
most at ammonia ions
some as titiratable acids
what happens to bicarbonate?
nearly all is reabsorbed to preserve the body supplies and be used as a buffer
what is the body net acid-base balance?
acidic
renal system makes slightly acidic urine pH5
what happen during kidney disease?
GFR down
how do the lungs regulate pH
by excretion of carbon dioxide
what does hyerpventilationc ause
decrease in hydogenions
and respiratory akalosis
what does hypoventaltion cause?
increase in hydrogen ions
respiratory acidosis
high H without renal buffing leads to
metabolic acidosis
low H without renal buffering leads to
metabolic akalosis
cause of metabolic acidosis
generation of hydrogen ion or loss of a base from the body
bicarb falls
compensation for metabolic acidosis
respiratory hyperventilation
loweres hydrogen
cause of respiratry acidsis
defective exchange of gasses in the lungs
carbon dioxide rises
copensation for respiraotry acidosis
renal
urinary reabsorption of bicarbonate
cause of metabolic alkalosis
loss of hydrogen ions or generation of bases in the body
rise in bicarbonate
compensation for metabolic alkalosis
respiratory hypoventialtion
raise hydrogen levels
cause of respiratry alkalosis
hyperventilation
carbo dixide falls
compensation for resiratory alkaosis
renal
urinaey secretion of bicarbonate
lose some bicarb
