SHolroydAtWeilCornellMedQatar/Urology/Kidney/Tubules/WaterReabsorption/ControlToSweating

POINT!

With sweating, the plasma osmolarity increases, and negative feedback increases the water reabsorption.

Before sweating (at baseline), we will make the assumption that the subject is in homeostasis with adequate strength of the plasma osmolarity-decreasing effect of water reabsorption as well as normal plasma and urine osmolarities (isotonic) and urine volume.

Step 1: With sweating, water leaves the plasma and osmolarity increases (concentrated, hypertonic).

Step 2: This is in the opposite direction to the plasma osmolarity-decreasing effect of the water reabsorption. Thus, although the strength of the plasma osmolarity-decreasing effect of water reabsorption was adequate before sweating (at baseline), this strength is now too weak (blue) to reverse the increased plasma osmolarity (concentrated, hypertonic) produced by sweating. Control by negative feedback is needed.

Step 3: With the strength of the plasma osmolarity-decreasing effect of the water reabsorption before sweating (at baseline) being too weak (blue), the negative feedback increases (red) the water reabsorption.

Step 4: With the increase in water reabsorption, diluted (hypotonic) solution enters the plasma. This will lead to a reverse in the increased plasma osmolarity (concentrated, hypertonic) produced by sweating, decreasing it towards normal (baseline, isotonic) osmolarity. Because diluted (hypotonic) solution leaves the tubule due to reabsorption, the fluid remaining in the tubule has increased osmolarity (concentrated, hypertonic). Also, with the increase in water reabsorption, there is less water remaining in the tubule. Overall, the urine becomes concentrated and decreases in volume.

Challenge Quiz

1.

With sweating, the plasma osmolarity increases, and negative feedback increases decreases  正解! the water reabsorption from the tubule.

2.

With sweating, the plasma osmolarity increases decreases  正解!. This is in the same direction as opposite direction to  正解! the plasma osmolarity-increasing osmolarity-decreasing  正解! effect of the water reabsorption from the tubule. The negative feedback increases decreases  正解! the water reabsoprtion from the tubule. This will increase decrease  正解! plasma osmolarity (towards isotonic).

3.

With sweating, water enters leaves  正解! the plasma and osmolarity increases decreases  正解!.This is in the same direction as opposite direction to  正解! the plasma osmolarity-decreasing effect of the water reabsorption . Thus, although the strength of the plasma osmolarity-decreasing effect of water reabsorption was too weak adequate too strong  正解! before sweating (at baseline), this strength is now too strong adequate too weak  正解! to reverse the increased decreased  正解! plasma osmolarity produced by sweating. The negative feedback increases decreases  正解! water reabsorption from the tubule. Thus, concentrated diluted  正解! solution enters the plasma. This will lead to a reverse in increased decreased  正解! plasma osmolarity from sweating, increasing decreasing  正解! it towards separate from  正解! normal (baseline) osmolarity. Because concentrated diluted  正解! solution leaves the tubule due to reabsorption, the fluid remaining in the tubule has an increased a decreased  正解! osmolarity. Also, with the increase decrease  正解! in water reabsorption, there is more less  正解! water remaining in the tubule. Overall, the urine becomes concentrated diluted  正解! and increases decreases  正解! in volume.