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Video transcript

- Even when you're resting, your brain and body are hard at work maintaining stability in your internal environment. It's a process called homeostasis. It's how you maintain your temperature, heart beat, metabolism, all that, even though external conditions change, and it's also a state your body strives for when you get out of balance. You've experienced this before if you've ever been exercising and you get out of breath and really hot and sweaty, and then afterwards, your body cools you off and lowers your heart rate. That's homeostasis at work. And it also works when you take drugs. So, for example, if you take amphetamines, which raise your heart rate, then your body quickly tries to lower your heart rate and get you back to normal, and what's really interesting, is how smart your brain is about this. If you're a regular drug user, then you probably have certain ritualistic behaviors that lead up to the drugs entering your body. For example, you might always take your drugs in a certain location, after eating, or a certain time of day. So, let's say you're a cocaine addict, and you're always in one particular room when you inject yourself with cocaine, it's your preferred method of entry, and it takes you a few minutes to set out your needle, set up your space, kind of get ready, and after a few times doing this, your brain starts to recognize that these external cues, like the room, the needles, the whole process of setting up, means that your body is about to get a nice big dose of drugs. So, rather than wait for the cocaine to enter your body and then start regulate your normal functions, your brain tells your body to get a head start. It starts lowering your heart rate before you even take the drugs, and that's why after a while your body needs a higher dose to reach the same high. Okay, so imagine you start out at a certain level, we'll call that homeostasis, and when your brain knows the drugs are about to come, it starts adjusting your bodily functions. So, it lowers your heart rate and metabolism, et cetera, and then it takes even more of those drugs to get up to your high point. But what would happen if you get all those cues, but then you don't get the drug? So, your body's already pre-adjusted, preparing to get the stimulant, but nothing comes to counteract the lower heart rate, lower metabolism. You would experience a crash, because there's no high to counteract that slowing down that your brain has initiated. Okay, so let's imagine the other side of it, though, that you're in a new location when you take drugs. So, your body doesn't have time to pre-adjust, but you take that same level of drugs, and that's why a lot of people overdose when they take drugs in a new location, because if their body doesn't know it's coming, it doesn't pre-adjust, but they take the same high level of the drug, then their body's not prepared for that amount, and it causes an overdose.