Question

Which of the following factors would cause an increased volume of urine production in man?
a. Humid day
b. More intake of water than usual
c. Drinking a large quantity of strong salt water
d. All of the above.

Answer 1

Our body has a fascinating yet sophisticated mechanism and system for the maintenance of optimum water- electrolyte balance in the blood. This is mainly achieved by kidneys. Kidneys are two bean-shaped organs involved in filtration of blood and urine formation.

Complete answer:
Let us first discuss urine formation.
So, as we all know, urine formation takes place basically by 3 steps or processes. They are-

Ultrafiltration - Blood entering the kidneys gets filtered by renal corpuscle under very high pressure. The resulting filtrate then passes through the renal tubules and down the loop of Henle.
Reabsorption - In the renal tubules, there is absorption of required ions and water molecules so as to maintain the osmolarity of blood.
Secretion - Unwanted and excess substances such as hydrogen ions, creatinine or drugs are removed from the blood.
The filtrate that finally remains after all these 3 steps is called urine.

Let us now understand the effect of osmolarity on the volume and concentration of urine.
So, the volume and concentration of urine depend largely on the relative quantity of fluid and solute particles in blood. In instances of less quantity of water or fluid (or increased solute concentration) in the blood, there is increased reabsorption of water from the renal tubules thus compensating for the less volume of water in blood. This results in the production of a more concentrated urine. The exact opposite happens if blood contains more than normal volume of fluid and lesser solute particles.

In humid conditions, water loss through perspiration is very less and thus urine production tends to increase. Intake of more water than normal also increases the volume of urine production as there will be less reabsorption of water. Body will also tend to excrete the excess water or salt by increasing urine production. Thus considering the above given options, all of them are correct.

Hence, the correct answer is option (D).

Note: Electrolytes in the blood need to be maintained in an optimum balance, as they are imperative for the body to function properly. Electrolyte imbalance of sodium, calcium, potassium, or magnesium in the body may be manifested in the form of weakness, convulsions or twitching. Severe electrolyte imbalance may also affect the vital functions of the body and cause serious problems such as cardiac arrest, seizures, and coma.