SHolroydAtWeilCornellMedQatar/Endocrinology/VasopressinADH/ControlToSweating

POINT!

Following sweating, the plasma osmolarity increases and negative feedback decreases the synthesis, secretion, and blood concentration of ADH.

narrated video explanation

ファイル:ADHbaseline.jpg

video prior to sweating
Prior to sweating (at baseline), we will make the assumption that the subject is in homeostasis with normal plasma and urine osmolarities (isotonic) and volumes.

video just after sweating
Step 1: With sweating, water leaves the plasma and osmolarity increases (the plasma becomes hypertonic).

Step 2: ADH, by increasing water channels, and reabsorption of water by the kidney, decreases plasma osmolarity. This is opposite to the effect of sweating. Thus, with the high plasma osmolarity produced by sweating (hypertonic plasma), the baseline strength of the plasma osmolarity-decreasing effect of ADH on the water channels and reabsorption would be too weak. Control by negative feedback is needed.

video just after the increase in ADH caused by sweating
Step 3: With the baseline strength of the ADH effect on water channels and reabsorption being too weak, the negative feedback increases the synthesis, secretion, and blood concentration of ADH.

Step 4: The elevation in blood concentration of ADH increases the number of water channels. This increases the reabsorption of water by the kidney.

video showing the changes in plasma and urine after the increase in ADH caused by sweating
Step 5: The ratio of Na⁺ to water entering the plasma during reabsorption decreases. This decreases plasma osmolarity. This will lead to the increased plasma osmolarity from sweating (hypertonic plasma) decreasing and returning towards normal (baseline). Because a lower ratio of Na⁺ to water leaves the tubule during reabsorption, the fluid remaining in the tubule has a higher osmolarity (hypertonic). Also, with an increase in water reabsorption, there is less water remaining in the tubule. Overall, the urine becomes more concentrated (hypertonic) and lower in volume.

Challenge Quiz

1.

Following sweating, negative feedback increases decreases  正解! (synthesis, secretion, and blood concentration of) ADH.

2.

Following sweating, negative feedback increases decreases  正解! water channels in the kidney.

3.

Following sweating, negative feedback increases decreases  正解! water reabsorption by the kidney.

4.

Following sweating, negative feedback increases decreases  正解! urine volume.

5.

Following sweating, negative feedback increases decreases  正解! urine osmolarity.

6.

Following sweating, negative feedback increases decreases  正解! plasma osmolarity.

7.

Following sweating, the plasma osmolarity decreases increases  正解!. The effect would be the same as opposite to  正解! that of ADH, water channels and reabsorption of water by the kidney, which decreases increases  正解! plasma osmolarity. The effect of (synthesis, secretion, and blood concentration of) ADH would be too weak too strong  正解! prior to control by negative feedback. Negative feedback increases decreases  正解! (synthesis, secretion, and blood concentration of) ADH. This in turn increases decreases  正解! the number of water channels in the kidney causing increased decreased  正解! water reabsorption. Urine osmolarity increases decreases  正解! while volume increases decreases  正解!. This decreases increases  正解! plasma osmolarity, returning to normal separating from normal  正解!.