Introduction/NegativeFeedback(MiddleLevel)/CarUphill

POINT!

With sweating the plasma osmolarity increases, and negative feedback increases the synthesis, secretion, and blood concentration of vasopressin (anti-diuretic hormone, ADH).

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 reabsorption (through the water channels, which are increased by vasopressin, ADH) as well as normal plasma and urine osmolarities (isotonic) and urine volume.

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

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

Step 3: With the strength of the plasma osmolarity-decreasing effect of the reabsorption (through the water channels, which are increased by vasopressin, ADH) before sweating (at baseline) being too weak (blue), the negative feedback increases (red) (the synthesis, secretion, and blood concentration of) vasopressin (ADH).

Step 4: The water channel-increasing effect of vasopressin (ADH) becomes stronger, which increases the number of water channels. This increases the reabsorption of water by the kidney.

Step 5: With the increase in water reabsorption, diluted (hypotonic) solution enters the plasma. This decreases plasma osmolarity. This will lead to a reverse in the increased plasma osmolarity from sweating (hypertonic plasma), decreasing it towards normal (baseline) osmolarity (isotonic plasma). Because diluted (hypotonic) solution leaves the tubule due to reabsorption, the fluid remaining in the tubule has a higher osmolarity (hypertonic). Also, with the 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.

With sweating, negative feedback increases decreases  正解! the synthesis, secretion, and blood concentration of vasopressin (anti-diuretic hormone, ADH).

2.

With sweating, negative feedback increases decreases  正解! the number of water channels in the kidney.

3.

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

4.

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

5.

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

6.

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

7.

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 reabsorption (through the water channels, which are increased by vasopressin, ADH). Thus, although the strength of the plasma osmolarity-decreasing effect of reabsorption (through the water channels, which are increased by vasopressin, ADH) 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 high plasma osmolarity produced by sweating. The negative feedback increases decreases  正解! (the synthesis, secretion, and blood concentration of) vasopressin (ADH). The water channel-increasing effect of vasopressin (ADH) becomes stronger weaker  正解!, which increases decreases  正解! the number of water channels. With the increase decrease  正解! in water reabsorption by the kidney, concentrated diluted  正解! solution enters the plasma. This increases decreases  正解! plasma osmolarity. This will lead to the 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 a higher lower  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 more concentrated diluted  正解! and higher lower  正解! in volume.