Physiology Flashcards
what is osmolarity?
concentration of osmotically active particles in a solution
body fluids osmolarity
300mosmol/L
what is tonicity?
effect a solution has on cell volume
define isotonic and its effect on the cell
same concentration solution
no change in cell volume
define hypertonic solution and its effect on the cell
concentrated salt solutions
decreases cell volume (shrinks cells)
define hypotonic solution and its effect on the cell
dilute solution
increases cell volume (swells, lysis)
two compartments of total body water
- intracellular fluid= 67%
2. extracellular fluid= 33%
what is the extracellular fluid made up of?
plasma (20%) interstitial fluid (80%)
tracer used to measure TBW
3H2O
tracer used to measure ECF
inulin
tracer used to measure plasma
labelled albumin
water homeostasis inputs
food
fluid
metabolism
water homeostasis outputs
skin lungs sweat faeces urine
what separates plasma and interstitial fluid?
capillary wall
what separates interstitial fluid and intracellular fluid?
plasma membrane
what ion is excluded from the ICF?
Na+
where is K+ usually located?
in ICF
changes can cause muscle weakness and cardiac problems
kidney functions
water balance
salt balance
plasma volume/ osmolarity
acid-base balance
excretion of waste/ exogenous foreign compounds
secretion of renin (BP) and erythropoietin (RBC)
conversion of vit D to active form
two types of nephrons
- juxtamedullary
2. cortical
do many nephrons empty into the same collecting duct?
yes
define urine
modified filtrate of blood
three filtration barriers
- glomerular capillary endothelium
- basement membrane
- slit processes of podocytes
what does the glomerular capillary endothelium act as a barrier against?
RBCs
what does the basement membrane act as a barrier against?
plasma proteins
what do the slit processes of podocytes act as a barrier against?
barrier to proteins
what GFR?
rate protein-free plasma is filtered from the glomeruli into Bowman’s capsule per unit time
what is a normal GFR?
125ml/min
what is a major determining factor for GFR?
glomerular capillary blood pressure
regulators of GFR
baroreceptor reflex
myogenic mechanism
tubuloglomerular feedback
what is tubuloglomerular feedback?
macula densa of DCT sense NaCl
define plasma clearance
measure of how effectively the kidneys clean the blood of a substance
normal renal plasma flow?
650ml/min
what is filtration fraction?
fraction of plasma flowing through the glomeruli that is filtered into the tubules and the rest moves to peritubular capillaries
what is transport maximum (Tm)?
point at which increases in concentration of a substance do not result in an increase in movement of a substance across a cell membrane
example of glucose’s Tm
2mmol/min (threshold is 10-12mmol/L, consider diabetes)
where in the nephron is most Na+ and water reabsorbed?
PCT
what channel in the PCT is water and Na+ reabsorbed?
Na+/K+ ATPase (water follows Na+, and Cl- follows)
where are glucose and amino acids reabsorbed in the nephron?
PCT
tubular fluid osmolarity in the PCT?
300mosmol/l
what does the loop of Henle enable the formation of?
hypertonic urine
what do the limbs of the loop of Henle function as?
counter-current multiplier
what happens in the ascending limb of the loop of Henle?
Na+ and Cl- are reabsorbed
impermeable to water
what happens in the descending limb of the loop of henle?
permeable to water
no other reabsorption
what do loop diuretics block?
triple co-transporter Na+/K+/2Cl- in the thick ascending limb
what cycle contributes to medullary osmolality?
urea cycle
how does the urea cycle contribute to medullary osmolality?
DCT is impermeable to urea and collecting duct absorbs about 50%
it can passively diffuse into the loop
what is the counter-current exchanger?
vasa recta
how do the vasa recta contribute to medullary osmolality?
run alongside the loop of Henle
have low blood flow to prevent NaCl and urea being washed away
what hormones control the distal tubule?
ADH
aldosterone
ANH/P
PTH
two parts of the DCT
early
late
what is in the early DCT?
triple co-transporter
what controls the late DCT?
aldosterone
what influences the collecting duct?
ADH by increasing the number of aquaporins to create concentrated urine
what causes ADH secretion?
hypothalamic osmoreceptors detect low BP
nicotine effect on ADH
stimulates
alcohol effect on ADH?
inhibits
where in the body secretes aldosterone?
adrenal cortex
what causes aldosterone to be secreted?
increased K+
reduced Na+
activation of RAAS
(low BP)
where is renin secreted from?
granular cells in JGA
what causes renin to be secreted?
reduced pressure in afferent arterioles
macula densa cells sense reduced NaCl in DCT
increased sympathetic activity in low BP
what happens if there is an abnormal increase in RAAS?
hypertension
fluid retention
when are ANPs produced?
when there is an increase in blood volume
what do ANPs do?
promote excretion of Na+ and diuresis
define water diuresis
increased water removal, not solute
define osmotic diuresis
increased urine flow as a result of salt excretion