Tears and Sweat Are Made of the Same Components?
What are tears made of? They are made of blood. They are made of plasma, the clear liquid part of blood excluding the red substance (hemoglobin). In fact, tears are clear blood. We shed "tears of blood" every day. Sweat is made of plasma, too. Technically, the components of sweat are not the same as those of tears. Sweat is filtered lest it should discharge some essential components included in plasma. Anyway, both of the two are made of blood and play an important role in supporting our lives.
The TRP channels detect heat, causing the brain to give instructions
We associate tears with sadness or joy. However, we shed them constantly to protect the eyes from bacteria and ultraviolet rays and nourish the surface of the eyes. The most important role of sweating is adjustment of body temperature. We sweat to lower the body temperature when the ambient temperature is high or we feel hot.
Our body feels hot with the TRP channel family of cell sensors, which detects the body temperature. Upon detection of heat, the brain gives an instruction to sweat to lower the body temperature.
We feel cool when TRPM8 detects cold and sends signals to the brain. The TRP channel that detects summer heat and causes sweating is different from the channel that detects cold temperature in an air-conditioned room.
"Painful sensation" caused by water entering the nose is a warning by another TRP channel
A runny nose is made of exactly the same components as tears. It expels viruses, pollen and other foreign matters entering deep into the nose. A sneeze, runny nose and stuffy nose are the body's defenses against foreign invaders.
You feel pain deep inside the nose when pool or bathtub water enters it. Another TRP channel is activated when detecting water with salt concentration different to body fluids. It warns us by causing pain that the cells are in danger.
This channel is called TRPA1. It is also activated by "pungency" of wasabi when you eat it. As one TV program indicated, the mechanism of "nasal pain" caused by pool water was disclosed by Mandom research.