Explain how the ADH affects the volume and concentration of urine.

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ADH is short for Antidiuretic Hormone. Antidiuretics are substances which reduce the production of urine to regulate the balance of fluid within the human body, leading to a decreased need to urinate. They are the opposites of diuretics, which increase the volume of urine and therefore lead to an increased desire to urinate. ADH is a hormone that belongs to the antidiuretics, as it leads to a decreased amount of urine production in the body. Therefore, the ADH level in the body plays a significant role with regard to the volume and concnetration of urine: a high amount of ADH in the body will lead to reduced frequency of urination and therefore more concentrated urine. On the other hand, the opposite would be the case if there were to be a low amount of ADH in the body: in this case, urine volume would increase and the concentration of urine would decrease.

This process is mainly linked to ion concentration. Once ADH has been produced, it will impact on the kidney nephrons, which are the filtering units of the kidney. The impact of ADH results in less plasma osmolarity, which is the ion concentration in the blood. As a consequence, more ions will be found in the urine (urine osmolarity). As a result of this process, parts of the nephrons suddenly begin to reabsorb water and to keep it in. This is the reason why ADH results in a reduced need to urinate, as the volume of urine has been significantly reduced by the process described. As a result of the decreased need to urinate, the volume of urine will be low and the urine will be more concentrated.

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