Final answer:
An increase in blood volume in the left atrium will stimulate ADH secretion. ADH acts on the collecting ducts in the kidneys to promote water reabsorption and reduce urine output.
Step-by-step explanation:
An increase in blood volume in the left atrium will stimulate ADH secretion. ADH, or antidiuretic hormone, is released by the pituitary gland in response to changes in blood volume and osmolarity.
When blood volume increases, it triggers the release of ADH, which acts on the collecting ducts in the kidneys to promote water reabsorption and reduce urine output.