Give biological reasons for the following statements:
There is frequent urination in winter than in summer.
Topic: Urination in winter and summer
Answer
In SUMMER the temperature is high, so a great deal of water is lost from the body as SWEAT through the skin. Less water is therefore left to be excreted by the kidneys, and the urine is scanty and concentrated.
In WINTER there is very little sweating, so the excess water must be removed by the KIDNEYS instead — giving more frequent and more dilute urination.
The answer must compare the TWO ROUTES by which water leaves the body — SKIN and KIDNEY — and show that they compensate for each other.
THE PRINCIPLE IS OSMOREGULATION: the total water lost must balance the water taken in, whatever the route. If the skin removes less, the kidneys must remove more.
The hormone doing the adjusting is ADH (vasopressin) from the posterior pituitary: when the body is short of water, ADH rises, the tubules reabsorb more, and the urine becomes scanty — which is exactly the summer condition.
It is a good example of how two organ systems cooperate to keep one variable steady.