Physiology Flashcards
osmolarity =
concentration of osmotically active particles in a solution
units for osmolarity in body fluids
mosmol/l
osmolality =
for weak salt solutions like body fluids is interchangeable with __
osmol/kg water
osmolarity
tonicity is related to osmolarity but also considers
the ability of a solute to cross the cell membrane
total body water = __% of body wt in M + F
60% males
50% females - more adipose tissue
ICF = ___% of total body water
67
ECF = +++
plasma (20%)
interstitial fluid (80%)
lymph and transcellular fluid (negligible)
tracers to measure volume of fluid compartments
total body water =
ECF =
plasma =
TBW = water ECF = inulin plasma = labelled albumin
equation for using a tracer to measure the volume of a fluid compartment
initial dose of tracer (mol) / sample concn (mmol/l) = volume (l)
insensible and sensible fluid losses
insensible = skin and lungs sensible = sweat, faeces, urine
in hot temperature and exercise lung loss of fluid __
hot = decreases exercise = increases
Na K Cl and HCO3 are higher or lower in ICF compared to ECF
in ICF - Na and Cl and HCO3 = lower
K = higher
main ions in ECF
Na Cl HCO3
main ions in ICF
K
Mg
-vely charged proteins
osmotic concns of ICF and ECF are __ at around __
equal
300mosmol/l
if gain NaCl ICF and ECF volumes __
ICF decreases
ECF increases
if gain isotonic fluid there is no __ change
ICF and ECF volumes __
osmolarity
ECF increase
ICF stays the same
> 90% of osmotic concn of ECF is from
Na salts = main determinant of ECF volume
> 95% of body __ is in ICF
so minor fluctuations in its __ concn => __+__
K+
plasma
paralysis + cardiac arrest
juxtaglomerular apparatus lies between __+__ in nephron
afferent and efferent arteriole
in cortical nephrons efferent arteriole > ___ > venules
peritubular capillaries
20% of nephrons =
80% =
20% = juxtamedullary nephrons 80% = cortical
key differences of juxtamedullary nephrons compared to cortical nephrons
juxta = longer loop of Henle
make more concn urine
single vasa recta that follows loop of Henle (rather that peritubular capillaries)
equation for rate of filtration of a substance
concn of X in plasma x GFR
normal GFR=
120-125ml/min
rate of excretion of a substance equation =
concn of X in urine x rate of urine production
rate of reabsorption of a substance equation =
rate of filtration - rate of excretion
rate of secretion of a substance equation =
rate of excretion - rate of filtration
glomerular membrane = ++_
glomerular capillary endothelium
basal lamina
slit processes of podocytes - glomerular epithelium
the glomerular capillary endothelium in the glomerular membrane is a barrier to ___ filtration
RBC
the basal lamina in the glomerular membrane is a barrier to ___ filtration because it is __ due to +
-ve plasma proteins
-vely charged
collagen and glycoproteins
forces that favour filtration that make up part of net filtration P
glomerular capillary bp (BPgc = 55mmHg)
Bowman’s capsule oncotic P (COPbc = 0)
forces that are against filtration that make up part of net filtration P
Bowmans capsule hydrostatic P (HPbc = 15mmHg)
capillary oncotic P (COPgc =30)
net filtration P = __mmHg
10
Starling forces are the balance of +
hydrostatic and osmotic forces
GFR definition
rate at which protein free plasma is filtered from glomeruli into bowmans capsule per unit time
GFR = ___ x ___
Kf (filtration coefficient “holiness”)
net filtration P
main determinant of GFR
stays constant along length of glomerular capillary due to ___
glomerular capillary bp
change in capillary diameter
extrinsic control of GFR is due to __
where decreased blood volume causes increased ___ => vaso__ and decreased ____+__
baroreceptor reflex
sympathetic activity
constriction
glomerular capillary bp and GFR
autoregulation/intrinsic control of GFR = __+__
myogenic response
tubuloglomerular feedback
bowmans capsule hydrostatic P increases if ___
causes GFR to
there is an obstruction => fluid build up in kidneys
decreases
capillary oncotic pressure increases if ___
causes GFR to
dehydrated
decrease
bowmans capillary oncotic pressure decreases if ___
causes GFR to __
burned => decreased plasma proteins
increases
plasma clearance definition
volume of plasma completely cleared of a particular substance per min = ml/min
plasma clearance = (__x__)/___
[X] in urine x volume of urine
[X] in plasma
clearance of __ = GFR
inulin
why is inulin a good measurement of GFR?
freely filtered at glomerulus not absorbed or secreted in nephron not metabolised by kidney not toxic easily measured in urine and blood
___ clearance is a close approximation of GFR
however some of it is ___
but it is ___ and so easier to measure than inulin
creatinine
secreted in nephron
endogenous
filtered, completely reabsorbed in prox tubule and not secreted
glucose
urea clearance is greater/less than GFR? because ?
less partly reabs (50%)
H+ clearance is greater/less than GFR?
because?
more
filtered, secreted from peritubular plasma + not reabsorbed
RPF (renal plasma flow) is calculated using __
PAH (para-amino hippuric acid)
exogenous organic anion used to measure RPF clinically =
PAH (para-amino hippuric acid)
PAH features that make it a good indicator of RPF
freely filtered at glomeruli
completely secreted into tubule
not reabsorbed
ie. completely cleared from plasma
filtration fraction = __/__ = __%
GFR/RPF
20% (125/650)
RBF = __ x __/__
RPF
1/1-haematocrit
RPF normally = ___ ml/min
650
__% of fluid and slat is reabs in kidney
99%
in proximal tubule ions and solutes are at ___ concn but there are no __/__
plasma
RBC/large proteins
__ml/min is reabs in proximal tubule so __ml/min is goes on to enter loop of Henle
80
45
in proximal tubule the reabsorbed fluid is ___ with the filtrate therefore there is no change in ___ as you go along the tubule
iso-osmotic
osmolarity
5 things reabs in proximal tubule
lactate glucose AAs sulfate phosphate
6 things secreted in proximal tubule
H+ toxins drugs eg. morphine uric acid bile pigments hippurates
NaKATPase is found at the ___ membrane in proximal tubule and increases ___ levels of K+ and __ levels of Na+
basolateral
intracellular K+
interstitial Na+
transporters at the luminal surface of proximal tubule for Na reabs
Na glucose
Na AA
Na H+ countertransporter
Na+ reabs in proximal tubule sets up an ___ gradient for Cl- to enter interstitial fluid ___ => ___ pull
electrical
paracellularly
osmotic
___ of peritubular plasma proteins causes H2O and Cl- reabs in proximal tubule
oncotic drag
transporters involved in glucose reabs at proximal tubule
luminal Na glucose cotransporter
basolateral glucose facilitated diffusion
__+___ systems in kidney are saturable and so once Tm is reached clearance is not __
reabsorption and secretory
constant
Tm (transport maximum) of glucose =
renal threshold therefore for plasma glucose =
2mmol/min
10-12mmol/l
__% of salt and water, __% of glucose and AAs are reabs in proximal tubule
67 salt and h2o
100 glucose and AA
loop of henle generates a ___ concn gradient to allow for production of ____
cortico-medullary solute
hypertonic urine
in loop of henle the medullary interstitial fluid is hypo/hypertonic
hypertonic
descending limb of loop of henle is highly permeable to ___ but no ___ reabs
H2O
no salt
in ascending limb of loop of Henle __+__ reabs
by __ in thick upper part and __ in thin lower part
is relatively impermeable to __
Na and Cl
active transport in thick
passively in thin
H2O
in thick ascending limb of loop of Henle there is the ___ cotransporter = blocked by ___
TALH triple (Na K +2Cl) loop diuretics
in thick ascending limb of loop of henle interstitial fluids osmolarity ____ => __ cant enter descending limb and H2O leaves it by osmosis => fluid in descending limb is __ and so salt __ => cycle repeats (countercurrent multiplier)
increases
interstitial solutes
concentrated
leaves into interstitium
___ fluid leaves loop of henle
hypoosmotic
50% of cortico-medullary gradient is contributed to by ___
urea cycle
other 50% = salt
urea cycle for loop of Henle:
urea ___ into loop > adds solute to ___ > distal tubule is not ___ to urea > collecting ducts ___ 50%(__ promotes this )
diffuses passively interstitium permeable reabs ADH
blood in vasa recta ___ with interstitial fluid across leaky endothelium
equilibriates
3 features of vasa recta that mean salt and urea arent washed away from loop of Henle =
hairpin
freely permeable to NaCl and H2O
blood flow to it is low
as vas recta goes down blood osmolarity __ and as it rises the osmolarity ___
increases
decreases
4 hormones that control Na reabs in distal tubule/collecting duct =
aldosterone
ANP
ADH
PTH
at resting state the distal tubule has low permeability to + and so ___ is concentrated in tubular fluid
urea and H2O
urea
process that occurs in early distal tubule =
NaCl reabs by NaK2Cl cotransporter
processes in late distal tubule and early collecting duct =
Ca2+ reabs
H+ secretion
Na + K reabs (in basal state)
the late collecting duct has ___ ion permeability and + permeability are influenced by ADH
low
urea and H2O
octrapeptide synthesised by supraoptic and paraventricular nuclei in hypothalamus =
ADH
type 2 ADH receptors are on ____ and ATP>cAMP => more ___
basolateral membrane of tubular cells
aquaporins inserted on luminal membrane
type 1 ADH receptors cause __
SM in arterioles to constrict
high concn of ADH in collecting duct => ___ H2O perm and ___ urine as ___ equilibriates with ___
low
hypertonic, small vol
tubular fluid with interstitium
most important stimulus of hypothalamus to release ADH =
hypothalamic osmoreceptors sense increased osmolarity
__ sitmulates ADH release and __+__ inhibit it (toxic substances)
nicotine increases
alcohol and ecstasy
aldosterone is secreted if __ increases/__ decreases in blood or __ is activated
K+ increases
Na decreases
RAAS
increased K+ directly stimulates adrenal cortex to release ___ which causes __
aldosterone
K+ secretion
decreased Na+ indirectly stimulates ___ release through __ causing RAAS activation
Aldosterone
juxtaglomerular apparatus
renin release = ___ sense low __ in distal tubule => increased __ to ___ cells and released
macula densa
sodium
sympathetic activity
granular cells
ATII effects =
aldosterone release
thirst
vasoconstriction of arterioles
aldosterone acts on luminal ___ and basolateral __
Na+
NaKATPase
__ is activated in HF due to low +
causes worsening of HF by __
Rx =
RAAS lbp and low CO retention low salt diet ACEI loops
ANP is produced by __ and stored in ___
heart
atrial muscle cells
ANP is released when ___ due to increased ___
atrial muscle cells are stretched
plasma volume
ANP => + increased, ___ decreased and afferent arteriolar vaso___ => increased GFR => + increased filtration and decreased ___ causing decreased CO and TPR
Na excretion and diuresis increased RAAS decreased dilatation Na and H2O filtration decreased sympathetics
blood pH 6.8 - &.35 =
acidotic
blood pH 7.45 - 8 =
alkalosis
3 ways in which H+ is constantly added to body fluids
carbonic acid formation inorganic acids (nutrient breakdown) organic acids (metabolism)
H2CO3 concn is dependent on ___ controlled by __
and HCO3- by __
therefore pH = __/___ function
PPCO2 - lungs
kidneys
kidneys/lungs
kidney - variable reabs of HCO3- and addition of HCO3- to blood depends on ___
H+ secretion into tubule
HCO3- reabs -
___ drives H+ secretion into tubule by ___ > + HCO3- > H2CO3 > + enter the cell > ____ > H2CO3 > H+ (secreted) + HCO3- -> ___ and enters interstitium
CO2 Na/H exchanger CO2 and H2O carbonic anhydrase basolateral Na/HCO3 cotransporter
when HCO3 in tubular fluid is low H+ combines with __
as H+ is still secreted this causes a net gain of ___
phosphate
HCO3 from cleavage intracellularly from H2CO3
titratable acid measures ___ largely as __ in urine
H+ excreted
H2PO4-
titratable acid = the amount of __ added to circulation as a result of its formation
bicarbonate
if severely acidotic tubular cells break down ___ from liver by ___ to form ___ which combines with H+ to form __ which is secreted in urine
glutamine
glutaminase
ammonia
ammonium
amount of ammonium secreted in urine is the same as ___ added to the blood as a result
bicarbonate
H+ excretion = + excretion = new __ generated
Titratable acid and ammonium
bicarbonate
normal bicarb plasma concns
22-26
normal PCO2 =
35-45mmHg
4.7-6kPa
compensation of AB balance =
restoration of pH irrespective of bicarb and PCO2
correction of AB balance =
restoration of pH and bicarb and PCO2
pH is directly proportional to __/___
[HCO3] / [CO2]
causes of resp acidosis =
COPD
airway restriction, opioids, chest trauma
in resp acidosis:
increased CO2 causes increased __+__ (proportionally more __)
H+ and bicarb
more H+
uncompensated resp acidosis pH and PCO2 =
pH <7.35
PCO2 > 45 mmHg
compensation by kidneys in resp acidosis
PCO2 drives H+ secretion and HCO3- reabs and formation
H+ is excreted as titratable acid and ammonium
causes of resp alkalosis =
low PO2 at altitude hyperventilation fever CNS damage anxiety
uncompensated resp alkalosis =
pH >7.45
PCO2 <35mmHg
renal compensation of resp alkalosis =
decreased CO2 causes decreased H+ secretion => decreased HCO3- reabs and none new formed - so lose bicarc
metabolic acidosis causes =
ingest acids
H+ production - lactic acid/ketones
diarrhoea
uncompensated metabolic acidosis =
pH <7.35
[HCO3-]plasma <22
compensation of metabolic acidosis by resp system
peripheral chemoreceptors stimulated by plasma pH
increase ventilation and decrease CO2
renal correction of metabolic acidosis =
decreased CO2 causes HCO3- reabs and fromation with H+ secretion
causes of metabolic alkalosis
vomit
ingest alkali
aldosterone hypersecretion
uncompensated metabolic alkalosis
pH >7.45
HCO3- concn plasma >26
compensation by resp system in metabolic alkalosis =
peripheral chemoreceptors see increased pH and decrease ventilation
correction by kidneys in metabolic alkalosis
not all bicarb is reabs and so decreased H+ secretion
urine is alkaline
