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blood pressure and urine production

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SysBio

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Need some help understanding the relationship....

Situation #1
Low blood pressure --> release ADH or Aldosterone --> increase water resorption --> increase blood pressure ---> decreased urine production (because water lost to body)

Situation #2
Stress/anxiety --> activate Sympathic nervous system --> release Adrenaline --> constrict blood vessels --> increase blood pressure --> increase urine production (because increased glomular filtration rate)


So is there a direct relationship between blood pressure and urine production?

In situation #1, high blood pressure means decreased urine....but in situation #2, high blood pressure meas more urine production
 

pm1

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Need some help understanding the relationship....

Situation #1
Low blood pressure --> release ADH or Aldosterone --> increase water resorption --> increase blood pressure ---> decreased urine production (because water lost to body)

Situation #2
Stress/anxiety --> activate Sympathic nervous system --> release Adrenaline --> constrict blood vessels --> increase blood pressure --> increase urine production (because increased glomular filtration rate)


So is there a direct relationship between blood pressure and urine production?

In situation #1, high blood pressure means decreased urine....but in situation #2, high blood pressure meas more urine production

I believe so, because an increase in BP increase the glomerular filtrate rate (that's what I learned from a full length I recently took).
 

rjosh33

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Need some help understanding the relationship....

Situation #1
Low blood pressure --> release ADH or Aldosterone --> increase water resorption --> increase blood pressure ---> decreased urine production (because water lost to body)

Situation #2
Stress/anxiety --> activate Sympathic nervous system --> release Adrenaline --> constrict blood vessels --> increase blood pressure --> increase urine production (because increased glomular filtration rate)


So is there a direct relationship between blood pressure and urine production?

In situation #1, high blood pressure means decreased urine....but in situation #2, high blood pressure meas more urine production

All else being equal, a higher blood pressure will cause a higher GFR and a larger urine output per unit time. However, when hormones like aldosterone and ADH are present, the higher blood pressure does NOT necessarily result in an increased urine output. This is because the hormones act on parts of the nephron that are distal to the glomerulus (aldosterone on the DCT, ADH on the collecting duct). So, although the blood is being filtered more quickly, the water (which makes up almost 95% of urine) is being resorbed, and so it never reaches the bladder.
 

pm1

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All else being equal, a higher blood pressure will cause a higher GFR and a larger urine output per unit time. However, when hormones like aldosterone and ADH are present, the higher blood pressure does NOT necessarily result in an increased urine output. This is because the hormones act on parts of the nephron that are distal to the glomerulus (aldosterone on the DCT, ADH on the collecting duct). So, although the blood is being filtered more quickly, the water (which makes up almost 95% of urine) is being resorbed, and so it never reaches the bladder.

hmm.. but wouldn't aldosterone and ADH not be released since the pressure is high?
I thought that the sensors at the macula densa (if I remember correctly) can tell if they need to reabsorb water (increase BP) or not - through aldosterone and vasopressing (renin-angiotensin). If GFR is high, there is no need to reabsorb. Thus, there would be an increase in urine output.
 

rjosh33

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hmm.. but wouldn't aldosterone and ADH not be released since the pressure is high?
I thought that the sensors at the macula densa (if I remember correctly) can tell if they need to reabsorb water (increase BP) or not - through aldosterone and vasopressing (renin-angiotensin). If GFR is high, there is no need to reabsorb. Thus, there would be an increase in urine output.

I suppose it depends on what time frame you're looking at, as well as the situation. If you're walking around with chronic high blood pressure, then chances are your filtration rate and urine output will be higher than a regular joe. But, if that increased blood pressure was caused by aldosterone or ADH secretion, then urine output immediately following actually decreases due to the mechanism by which these two hormones work.

So, with either of these two present, there is an increased blood pressure but a decrease in urine production. I suppose eventually, the higher blood pressure causes urine to be formed more quickly, but that's kind of a different situation.
 
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