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How does vasopressin regulate fluid volume in the body?
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Hormone
Many important physiological functions of vertebrates are controlled by steroid hormones.
Vasopressin, also known as antidiuretic hormone (ADH), regulates fluid volume by maintaining osmolality and responding to changes in blood volume.12
Mechanisms of Regulation
- Osmoreceptor Feedback: Specialized osmoreceptors in the hypothalamus detect shifts in serum osmolality. If osmolality increases (e.g., due to dehydration), the pituitary gland releases more vasopressin. If it decreases (e.g., overhydration), secretion is inhibited to promote water excretion.12
- Renal Action: In the kidneys, vasopressin acts on the collecting ducts. It triggers the fusion of aquaporins (water channels) with the cell membrane, making the ducts permeable to water. This allows water to be reabsorbed into the circulation, concentrating the urine and conserving body fluid.12
- Baroreceptor Response: Baroreceptors in the heart and arteries monitor blood pressure. A drop in blood volume reduces the stretch on these receptors, stimulating vasopressin release to help restore volume. Conversely, high blood volume inhibits secretion to increase water loss.12