conservation
"Okay," said his sister, "but then what about all the stuff that happens in the brain? The stuff the synapses carry?"
"What about it?"
"Well like, that's a lot of energy I would think. Where does it go?"
The question annoyed him - in part because he hadn't thought about it before, but mostly because, despite not being sure of the truth, he was sure that it was a stupid question.
He didnt know. He didnt know at all, but he answered. "That's transformed into heat that the body gives off right as it dies. And then the rest of the energy goes to the bacteria, which eat the body from the inside... and all the energy they get from eating the insides turns into gas, which they then fart out." The disbelieving expression on her face made him very tired. He would have fallen asleep right then and there, but he didn't want her to draw dicks all over his face afterward.