Physiology Flashcards
Osmolarity
Concentration of osmotically active particles in a solution
Units of osmolarity
Osmol/L
Mosmol/L for body fluids
2 known factors needed to calculate osmolarity
Molar concentration
No. of osmotically active particles
tonicity
Affect solution has on a cell
affect on cell in hypotonic solution
Solution has lower solute and higher water concentration than the cell
The cell gains water
Lysis (cell bursts)
affect on cell in hypertonic solution
Solution has a higher solute concentration and lower water concentration than the cell
The cell loses water
Shrinks
Affect of urea on RBCs
Urea is hypotonic
Cell lysis
Compare ion composition of ECF + ICF
ECF high in Sodium + chlorine + bicarbonate
ICF high in potassium + magnesium
how does 0.9% saline affect osmolarity and ECF volume
NO CHANGE in osmolarity
Changes ECF volume
Tracer used for full body water
3H20
Tracer used for ECF
Inulin
Tracer used for plasma
Labelled albumin
Which starling forces favour filtration
Capillary hydrostatic pressure (55mg)
Bowmans oncotic pressure (0mg)
which starling forces oppose filtration
Capillary oncotic (30mg) Bowmans hydrostatic (15mg)
how does Diarrhoea affect GFR
Increases capillary oncotic pressure so decreases GFR
How does a renal stone affect GFR
Increases bowman hydrostatic pressure so decrease GFR
how does afferent arteriole dilation affect GFR
Increases GFR
What causes afferent arteriole dilation
Prostaglandins
ANP
Which drugs cause constriction of afferent arteriole
What is the effect on GFR
NSAIDS
decreased GFR
Which drugs cause dilation of efferent arteriole
What is the effect on GFR
ACE/ARBS
decreased GFR
How does efferent arteriole constriction affect GFR
Increased GFR
What causes efferent arteriole constriction
ANP
Angiotensin 2
Norepinephrine
clearance is greater than GFR
substance is secreted
Clearance is less than GFR
substance is partially reabsorbed
clearance of what substance = GFR
Inulin
Why is glucose clearance 0
It is filtered and completely resorbed
what is PAH
Marker used to calculate renal flow
what needs to happen to a substance for it to be used as a marker of renal flow
needs to be completely secreted
what needs to happen to a substance for it to be used as a marker for GFR
needs to be freely filtered and neither secreted nor reabsorbed
what is filtration factor
Fraction of plasma flowing through the glomeruli that is filtered into tubules (20%)
where does most of reabsorption happen
proximal tubule
what is absorbed in descending limb of loop of henle
water
what is absorbed in ascending limb of loop of henle
NaCl
What does the loop of henle generate
cortico-Medullary concentration gradient
primary active transport
energy directly required
secondary active transport
substance transported coupled to concentration gradient of an ion (usually sodium)
what do loop diuretics block
Na-K-Cl co transporter
function of K+ recycling
Ensures NaCl is absorbed into interstitium
Which tubule is not permeable to urea
Distal tubule
Sodium resorption affects chlorine in what way
drives Cl resorption through paracellular pathways
filtration equation
plasma concentration x GFR
Resorption equation
Rate of filtration - rate of excretion
Excretion equation
(filtration+ secretion) - resorption
Secretion equation
Rate of excretion - rate of filtration
Functional unit of kidney
Nephron
Differences between the 2 types of nephron
Juxtamedullary- long loop of henle, has a vasa recta
Cortical- short loop of henle
Which nephron concentrates urine
Juxtamedullary
Which cells in juxtamedullary nephron secrete renin
Granular cells
Which cells sense sodium concentration of distal convoluted tubule
macula densa
Where is a fall in renal perfusion pressure detected
Baroreceptors in afferent arteriole
Function of ADH
Increases water reabsorption
Function of aldosterone
Increases Na absorption, increased K+ excretion
Function of ANH
Decreases Na absorption
Where is ANH produced + when is it released
Heart, stored in atrial muscle cells
Released when atrial cells are stretched due to Increased circulating volume
Causes increased sodium excretion therefore water is loss and plasma volume decreases
High levels of ADH
High water permeability
Hypertonic urine i.e. small volume of concentrated urine
Low levels of ADH
Low water permeability
Hypotonic urine i.e. large volume dilute urine
affect of atrial pressure on ADH
Decreased atrial pressure increased ADH release
Water diuresis
Increased urine flow but not an increase in solute excretion
Where do loop diuretics act
Thick portion of ascending limb of henle
where do thiazide diuretics act
Distal convoluted tubule
Where does aldosterone act
Distal convoluted tubule
Where does PTH act
Distal convoluted tubule
Where do carbonic anhydrase inhibitors act
Proximal tubule
What is the action of carbonic anhydrase inhibitors
Causes bicarbonate loss
where do ADH and ANP act
Collecting duct
where are aquaporin receptors found
apical membrane
Is distal tubular fluid hypo/hyper osmolar
hypo
relationship between atrial pressure and ADH
Decreased pressure, Increased ADH
affect of Nicotine on ADH
Stimulates ADH release
affect of alcohol on ADH
Inhibits ADH release
where is H+ secreted
distal convoluted tubule
which is more alkali arterial or venous blood
arterial
average ph of blood
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