Final answer:
Drinking 16 oz of water generally lowers blood osmolarity, leading to inhibited secretion of ADH, resulting in a greater urine volume and a more dilute urine solute concentration.
Step-by-step explanation:
When a physiology student drinks 16 oz of water in a short period, such as 15 minutes, the blood osmolarity would decrease due to the dilution effect of the additional water. Consequently, antidiuretic hormone (ADH) secretion would be inhibited because there is less need to conserve water. With reduced circulating ADH, the kidneys would decrease water reabsorption, resulting in an increased urine volume. Simultaneously, aldosterone secretion would likely also be inhibited, as its role in increasing sodium and water reabsorption to increase blood volume isn't needed when fluid intake is high.
In terms of urine concentration, a decrease in ADH leads to a decrease in the permeability of the collecting ducts in the kidneys to water, meaning that more water remains in the filtrate and is excreted as urine. This will result in the production of a larger volume of more dilute urine. Hence, the solute concentration of the urine would be lower. This relation between urine volume and concentration to ADH and aldosterone reflects the body's homeostatic mechanisms that regulate fluid balance and osmolarity.