 So having an effect, neurotransmitter causing an action in an effector or causing another action potential in a postsynaptic neuron, we have an effect. But here's the thing. If you just dump neurotransmitter into the synapse and it stayed there, it would keep on stimulating an effect. Does that work for you? Dude, if you keep on stimulating an effect, you have basically no control. The nervous system doesn't work like that. So as quickly as an action potential can travel down a neuron and dump neurotransmitter into the synapse, it removes the neurotransmitter just as fast. That way, if I want to send the message again, I'm going to send another action potential and dump more neurotransmitter. I'm not going to end up with like, I'm going to send this really precise specific message, go, and then end up with this kind of oozy, like who knows how long it's going to last, how long is the neurotransmitter going to hang out in that synapse, maybe till it just diffuses away, see you later, it might take a while. I'm going to send the message and then clean up immediately after so I can send another message. It allows for more precise control to how do we get the neurotransmitter out of there. Well, there's a couple of strategies that we can use. Number one, here's our job. Get rid of the neurotransmitter. Strategy number one, reabsorb it into the pre-synaptic neuron, pre-synaptic neuron. That's a great strategy. There are little, possibly, receptors that can bind with my neurotransmitter and reverse the process. Dude, that was endocytosis, aka, yumpscialization. Just yumpscialize the neurotransmitter and get it back into that neuron. Do, you know, if you need to process it again or whatever, but you can actually reuse it if you want. It's one way to get rid of it, another way. Remove it, chop it up with an enzyme. Dude, let's throw some Pac-Man's in there. Here comes Pac-Man. Here comes another one. And they go, just like that, complete with those sound effects and they yumpscialize all the neurotransmitter and they go, oh, my, my, no more effect. The neurotransmitter's gone. We can also, there's one more. Oh, the glial cells can actually clean up. The astrocytes, the microglia, they can actually come along and help remove neurotransmitter from the synapse. That's one of the reasons why, you know, the neuron, the star of the show. But glial cells, whoa, there's 90% of all of your neural tissue is made up of glial cells. They're probably pretty important. And the act of removing neurotransmitter, that's a really important job. So now, we're going to take a closer look at some specific neurotransmitters, specific neurotransmitters that we're going to see throughout the rest of the course, acting in specific scenarios. So let's start out by looking at acetylcholine.