Tolerance is how strongly our bodies react to the effects of a given substance. We develop tolerances because human bodies are highly adaptive, and that includes adapting to the things we consume. As we consume cannabis, our bodies adjust to the cannabinoids over time, resulting in less potent effects. When our bodies intake more cannabinoids than they usually would, these systems leap into action to respond. Without regulating systems in place, we may never stop being hungry, or might never feel rested. They exist to help us maintain homeostasis. However, the same systems will react to an abundance of cannabis cannabinoids. The more cannabinoids we throw at them, the more they will respond to mitigate them. With less available receptors and a weaker response, our bodies react less, and the effects of cannabis are reduced. Consequently, we would need to take in more cannabinoids to have the same level of effect that happened when more receptors were available. As a result, our tolerance goes up.