Video Transcript
On a hot day, what would you expect
to happen to the volumes of sweat and urine which are excreted? (A) The volume of sweat would
decrease, and the volume of urine would increase. (B) The volume of sweat would
increase, and the volume of urine would decrease. (C) The volumes of both sweat and
urine would increase. (D) The volumes of both sweat and
urine would decrease.
This question is asking us about
two different excretions from the body, sweat and urine, excreted by the skin and
kidneys, respectively. Both of these organs belong to the
excretory system, which is responsible for removing excess or harmful waste products
from the body.
Here we can see a sweat gland in a
section of skin in the diagram. Sweat is primarily made up of
excess water that the body can get rid of in addition to other wastes, including
minerals, ions, and urea. When sweat is produced, it can
actually help to cool the body due to a phenomenon called evaporative cooling. This occurs as the water that is
excreted as sweat absorbs heat from the body and evaporates from the skin. On a hot day, the body may
overheat, so it produces sweat to try and cool the body down. This results in an increase in
sweat volume.
Here we can see a diagram of the
kidneys, which produce urine after filtering different wastes from the blood. This urine is stored in the bladder
until it is expelled by urination. On a hot day, we’ve just learned
that sweat production increases. Because of this, the overall amount
of water available in the body decreases. Because there’s a lower amount of
water available, less water will be excreted in the urine in order to conserve water
for the body. So the volume of urine will
decrease.
Getting back to our question, on a
hot day, the option that correctly identifies what would happen to volumes of sweat
and urine is given by answer choice (B). The volume of sweat would increase,
and the volume of urine would decrease.
