Question

Why vasopressin is not secreted when a person drinks a lot of water

Answer 1

Vasopressin or antidiuretic hormone is one of the hormones that is used by the body to regulate the loss of water from the body. Vasopressin hormone inhibits diuresis, that is to say loss of urine. It is thus important for retention of water in the body. It is only used by  the homeostatic system when the body is experiencing dehydration. Dehydration also cause low blood pressure, this is why vasopressin which is a vasoconstrictor, is used by this system to correct the low blood pressure... hope it is helpful... plz mark my answer as brainiest

Answer 2

Vasopressin is also known as Anti-diuretic hormone. 

The main function of ADH is water retention. It causes absorption of water from distal convoluted tubule and collecting duct. In absence of ADH these ducts and tubules are impermeable to water and hence the water reabsorption does not occur which results in excretion of dilute urine.


In order to know 'why ADH is not secreted when a person drinks lot of water' lets look at the mechanism of ADH secretion.

Mechanism:
ADH secretion depends upon volume of body fluid and osmolarity of body fluids.
Potent stimulants for ADH secretion are: 1)decrease in extracellar fluid volume.
  2) increase in osmolar concentration in ECF.

 Role of osmoreceptors:

These osmoreceptors are receptors which give response to change in osmolar concentration of blood.

These receptors are situated in hypothalamus near supraoptic and paraventricular nuclei.

When osmolar concentration of blood is increased it stimulates the receptors and these receptors in turn will stimulate the supraoptic and paraventricular nuclei which sends impulses to posterior pituitary and causes release of ADH.

ADH causes reabsorption of water which restores the normal osmolarity and the normal ECF.



Thus, the secretion of vasopressin or ADH depends upon less body fluid in our body so it is not secreted when a person has drinks lot of water instead the body tries to excrete the excess water by decreasing reabsorption of water.

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