Physiology 9 Flashcards
What does GFR show us about the kidney?
It shows us how well the nephrons of the kidney are functioning.
What is the normal GFR per minute?
125mls/min.
what is the normal decline in GFR with ageing?
After 30, GFR declines at 1ml/min per year.
how much less is women GFR in comparison to men?
10% less
What does it mean that the kidneys have a high reserve capacity?
you can loose a lot of nephrons before GFR is affected, and your GFR has to recuse greatly before osmolarity is affected.
What was the first way of measuring GFR?
By measuring inulin clearance? Because it is filtered, but NOT reabsorbed or secreted.
What is the new way to measure GFR?
Creatinine clearance - creatinine is a breakdown product of the muscles creatine.
What will the clearance be in comparison to inulin if something is reabsorbed?
Less, because some of the plasma which has been cleared will be stuck with the reabsorbed substance.
What will the clearance be in comparison to inulin if something is secreted?
Higher, because theres more filtered product so less of the plasma has been filtered
What will happen to drugs if GFR declines?
drugs might not be excreted as efficiently, we might have to reduce the drug dose in order to prevent drug toxicity from occurring.
What does a decline in GFR suggest?
a decline in nephron function
is the creatinine and GFR relationship linear or curved?
It is curved, this means that a reduction in GFR won’t always be displayed by creatinine clearance levels.
Eg - GFR needs to drop by 50% to see a reduction in creatinine clearance.
What is eGFR?
this is the estimated GFR - this uses equations and measures creatinine clearance more accurately, taking into account the curved relationship.
What causes an increase in creatinine?
Increased muscle mass - increased creatine turnover
Creatine supplementation
What causes a decrease in creatinine?
Vegetarian - they don’t get much creatinine from food.
what should normal glucose clearance be?
0 - all glucose should be reabsorbed (unless theres too much)
What should normal urea clearance be?
50%
What is the importance of PAH? parraamino-hippuric acid?
Over 90% of PAH is filtered with each round of GFR - therefore by measuring PAH clearance, you know roughly the amount of plasma that is filtered in one round of Glomerular filtration.
What does parasympathetic nerves do regarding micturition?
They cause an increase in micturition, they increase detrusor muscle contraction.
What does the sympathetic nerves do regarding micturition?
causes constriction of the internal urethral sphincter, inhibits bladder detrusor muscle contraction.
what do somatic motoneurons do regarding micturition?
They cause relaxation and contraction of the external urethral sphincter (even against strong urges to pee)
What is the trigone?
The 1 urethral opening
the 2 vesicoureteric openings
What is the main muscle of the bladder?
The detrusor muscle
how does the female urethra empty after micturition?
by gravity
How does the male urethra empty after micturition?
via the bulbocavernosus muscles.
When do higher brain centres NOT have an effect on micturition?
in babies or paraplegic patients.
At what volume does the increase to void increase?
400-500mls
Explain the steps in the micturition reflex?
increase in urine in the bladder (400-500)
- causes an increase in parasympathetic nerves (increasing bladder muscle contractions)
- inhibition of the sympathetic nerves (relaxation of internal urethral sphincter)
- motoneurons - controlled by higher brain centres - you can relax or contract the external urethral sphincter depending on whether you want to micturate.
- parasympathetic activity inhibits the sympathetic activity and contraction of external urethral sphincter (it gets easier to pee and harder to fight it off).
