Which of the following statements best describes the principle of mass balance?

a. The amount of a variable that is gained by the body through ingestion equals the amount that is lost from the body.

b. The body maintains a stable mass at all times.

c. The amount of each variable brought into the body must be balanced by all other variables.

d. The amount of a variable ingested is regulated by a positive feedback loop.

Video transcript

Welcome back everybody. Our next question says, which principle governs water balance in the body? A principle of equilibrium B principle of mass balance, C principle of energy or D principle of diffusion. When we think specifically about water balance in the body, we're thinking about the fact that water intake that occurs through drinking and eating should equal the water leaving the body through urination, sweating, breathing out water vapor. So when we think about that, that we're talking about the amount of water coming in versus the amount of water coming out. That would be choice B the principle of mass balance that the mass of something gained by the body must be then lost by the body. When we look at our other answer, choices, uh perhaps the most tempting is choice a, the principle of equilibrium because we're started talking about a state of balance and equilibrium would refer to that state where things are at a steady state or balance, but that equilibrium state can be reached lots of different ways. Um And if we're specifically talking about water and how it comes into and leaves the body, it's more about the amount the mass of it. So choice isn't really specific enough for what we need. Choice. C principle of energy would just be that the, there's that matter, that law of energy conservation, it can't be created or destroyed. But here we're simply talking about taking in water, expelling water. We're not talking about things like metabolism where you're converting, for instance, chemical energy into other forms of energy. So Tracy not correct. And finally, choice D principle of diffusion that something will move from an area of higher concentration to lower concentration. And while diffusion is obviously a really important part of water's functions in the body, osmotic pressure is something that's very key for lots of bodily functions. Specifically, this idea of water balance taking in water, water leaving is not the principle of diffusion is what governs that overall balance. So choice D is not a correct answer. So this was a little bit of a nebulous one. But if we recall that we're talking about overall in the body, how water comes in, how water goes out? We are talking about the principle of mass balance or Choice B. See you in the next video.