Final answer:
Vasopressin, or Antidiuretic hormone (ADH), is secreted when the concentration of solutes in the interstitial fluid is high. It prompts the kidneys to reabsorb more water, decreasing urine output and increasing blood pressure.
Step-by-step explanation:
Vasopressin, or Antidiuretic hormone (ADH), is secreted when:
C. the concentration of solutes in the interstitial fluid is high.
The cell bodies of neurons that produce ADH are located in the hypothalamus. When the solute concentration, or osmolarity, in the blood increases, it reflects a decrease in water concentration. This can occur when there's dehydration or loss of blood volume. Osmoreceptors within the hypothalamus detect the high osmolarity and stimulate the secretion of ADH. The purpose of ADH is to conserve body water by prompting the kidneys to reabsorb more water, thus decreasing urine output. It achieves this by making the collecting ducts in the kidneys more permeable to water, allowing water reabsorption back into the blood. By doing so, ADH helps to restore blood volume and pressure and reduce the concentration of solutes in the blood to within normal ranges, which acts as negative feedback to reduce ADH secretion.
ADH also acts as a vasoconstrictor that helps to increase blood pressure during hemorrhaging, which further emphasizes its role in conserving body water and maintaining blood pressure.