Question

Comment upon the hormonal regulation of selective reabsorption.

Answer 1

• When there are changes in blood volume, body fluid volume, and ionic concentration the osmoreceptors are activated.
• This happens during an excessive loss of fluid from the body.
• The activated osmoreceptors stimulate the hypothalamus to release antidiuretic hormone [ADH] or vasopressin.
• This in turn promotes the reabsorption of water from later parts of the tubule, thus compensating for the fluid loss.
• When the fluid present in the body increases the osmoreceptors sense it and switch off the ADH.
• Renin from the juxtaglomerular apparatus also enhances the reabsorption of water.