physiology Flashcards
(228 cards)
what is the horizontal gradient between levels of the loop of Henle
200 mOsmol
how do stretch receptors in the bladder control micturition (babies/ spinal injuries)
become distended as the bladder fills (300- 350mls) until their output is large enough to stimulate parasympathetic system and relax external sphincter by inhibiting somatic neurones
what effect does hyperkalaemia/ hypokalaemia have on the body cells
hyperkalaemia - >5.5 - lower r.m.p –> ventricular fibrilation
hypokalaemia - <3.5 - increase r.m.p –> hyper polarise cells –> cardiac arrythmias
when the renal artery constricts what hormone is released
Renin
what is the HCO3 in blood
24 mmoles/ L (22- 26)
what is the pH of blood and how many H ions are free
7.4 (7.37 - 7.43)
4 x 10-6 mmoles/L free H - contribute to pH
what is the henderson hassebalch equation for pH
pH = HCO3/ PCO2
if a substance has a lower clearance that inulin what will happen
filtered and reabsorbed
[Ux] lower, [Px] higher
how do changes in osmolarity affect osmoreceptors
increases osmolarity - water out the cells, cells shrink, increased neural discharge
decreased osmolarity - water in the cells, cells swell, decreased neural discharge
what is the anion gap
difference between the sum of principal cations (Na and K) and principle anions (Cl and HCO3) in the plasma
normally 14-18 mmoles/L
what is the filtration fraction of the kidneys
19%
GFR/ Renal plamsa flow (55% of BV) x 100 = 125/660 x 100
when the mean arterial blood pressure increases, what happens to the afferent arteriole?
constricts - prevent rise in glomerular pressure
describe the process of ammonium excretion
in renal tubule cells - deamination of glutamine by renal glutaminase enzyme produces NH3
NH3 moves out tubule to combine with secreted H (fro CO2 in blood)
NH4 is formed in lumen which combines with Cl and NH4Cl is excreted in distal tubule
how does a metabolic alkalosis occur
HCO3 increase
what is the minimum and maximum pH of urine
min - 4.5-5
max - 8
what is used to estimate GFR
creatinine clearance
eGFR = 1/ [PCr]
in antidiuresis, how is urea retained to save water
reabsorbed from collecting duct into interstitium where it reinforces the interstitial gradient in the loops of Henle
if molecules X has filtration < excretion what will be the renal handling of X
net secretion
how do osmoreceptors regulate ADH secretion
increased osmolarity increased neural discharge mediated by osmoreceptors in the anterior hypothalamus
what is the mechanism for reabsorption of HCO3
active H secretion from tubule cells coupled to passive Na reabsorption
filtered HCO3 reacts with H to form H2CO3
with carbonic anhydrase this is converted into CO2 and H20
CO2 freely permeable and enters the cell
within the cell CO2 forms H2CO3 which dissociates to H and HCO3
the HCO3 ions pass into the peritbular capillaries with Na
(1 for 1 - no net gain)
how does increased sympathetic nerve activity impact renin release
increase release (B1 effect)
why can a big blood transfusion cause a metabolic alkalosis
bank blood contains citrate to prevent coagulation which is converted to HCO3
in the absence of ADH, what happens to water in the collecting duct
impermeable to H20 so large volumes of dilute urine are lost (compensate for H20 excess)
where does the majority of respiratory acid get buffered
97% within cells
rest within plasma proteins