Endocrinology/VasopressinADH/ControlToWaterIntake

POINT!

With water intake, plasma osmolarity decreases, and negative feedback decreases vasopressin (anti-diuretic hormone, ADH) synthesis, secretion, and concentration in blood.

narrated video explanation

Before water intake, there are 3 columns (illustration) of water reabsorption (water entering the plasma through the water channels, that are increased by vasopressin, ADH, which has certain levels of synthesis, secretion, and concentration in blood), as well as 3 columns (illustration) of Na⁺ reabsorption (by the Na⁺ pump). Plasma and urine osmolarity are normal (isotonic).

1st star (illustration): With water intake, water enters the plasma, and plasma osmolarity decreases (becomes diluted, hypotonic).
Movement of water with water intake is in the same direction as water reabsorption (water entering the plasma, through the water channels, that are increased by vasopressin, ADH).

②-1 (illustration): Since the movements of water (entering the plasma) with water intake and with water reabsorption (water entering the plasma, through the water channels, that are increased by vasopressin, ADH) are in the same direction, negative feedback decreases vasopressin (anti-diuretic hormone, ADH) synthesis, secretion, and concentration in blood.
②-2 (illustration): The water channel-increasing effect of vasopressin (ADH) weakens, and the number of water channels decreases.
②-3 (illustration): With the decrease in water channels, water reabsorption from the tubule decreases from 3 to 2 columns (illustration).

③(illustration): With no change in Na⁺ reabsorption, and the decrease in water reabsorption, concentrated (hypertonic) fluid enters the plasma. Because of this control, the decreased plasma osmolarity increases (towards that before water intake, or isotonicity).

Namely, the initial change (the decrease in plasma osmolarity) decreases (blue downward unfilled arrow disappears).

Because concentrated (hypertonic) fluid (of 3 columns of Na⁺ and 2 columns of water) leaves the tubule with reabsorption, the osmolarity of the fluid remaining in the tubule (urine) decreases (becomes diluted, hypotonic). Also, with the decrease in water reabsorption (water leaving the tubule), the volume of water remaining in the tubule (urine) is more. Overall, the urine becomes diluted and increases in volume.

Challenge Quiz

1.

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

2.

With water intake, 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 (through the water channels, which are increased by vasopressin, ADH). Negative feedback increases decreases  正解! (the synthesis, secretion, and blood concentration of) vasopressin (ADH). This will increase decrease  正解! plasma osmolarity (towards isotonic).

3.

With water intake, 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 (through the water channels, which are increased by vasopressin, ADH). Thus, although the strength of the plasma osmolarity-decreasing effect of water reabsorption (through the water channels, which are increased by vasopressin, ADH) was too strong adequate too weak  正解! before water intake (at baseline), this strength is now too strong adequate too weak  正解! to reverse the increased decreased  正解! plasma osmolarity produced by water intake. 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 increases decrease  正解! in water reabsorption from the tubule, concentrated diluted  正解! solution enters the plasma. This will lead to a reverse in the increased decreased  正解! plasma osmolarity from water intake, increasing decreasing  正解! it towards separate from  正解! normal 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.