 So all of these topics that we're talking about today are, I don't know, tools in our toolbox that will let muscles work together and do all these really amazing, fine things in a coordinated manner. Like, whoa, we have so much control over our muscles and we don't even think about like a bouncy stair step and we don't even use tetanus. Like, we don't even know that that's happening in our myofibers because we're so, we're so good. We're that good. Well, another tool in our toolbox is this concept of the motor unit. The motor unit is my friend. One somatic motor neuron. Here's my somatic motor neuron with its cell body in the lateral gray horn. I mean, in the anterior gray horn of the spinal cord. And all of the skeletal muscle fibers, it innervates. Oops, that wasn't the right direction for my little axon terminal. Okay, looks like a little octopus. That was the word I was trying to come up with. Look, now this looks like a blood cell, but it isn't. That's a myofiber. That's a skeletal muscle cell. I made it look like a skeletal muscle cell. This is a pack of skeletal muscle cells. And so this is highly anatomically diagrammatic, but I just want you to see that one somatic motor neuron can actually innervate, please don't think these are blood vessels because they aren't. I'm recording right now. They can innervate. They can branch. Most of them do, many times. One somatic motor neuron, plus all the myofibers. It innervates. That's a motor unit. So I've drawn you one motor unit. This motor unit has four myofibers in it. So one somatic motor neuron plus four muscle cells. And here's the deal. Myofibers, they range in size. They can be four muscle cells. So one message from a neuron is going to stimulate the contraction of four muscle cells. That's one motor unit. Or they could be 4,000 muscle cells. What? One message from one somatic motor neuron. Here comes the action potential. Folks, here it comes. My action potential is on its way. And then, I mean, all that's happening here is that my axons are splitting. And at that place, all the voltage-gated sodium channels in all of these branches are going to be opening because they're going to be stimulated by the voltage at this point. And so the action potential is going to travel down all of those axons and reach 4,000 myofibers and stimulate contraction, one contraction in all of them. How cool is that? You can imagine that if I send a message, contract fellas to four muscle cells, I'm going to get a nice little fine contraction. If I send a contract fellas message to 4,000 muscle cells, I'm going to get this like, whoa, that was a huge contraction. There was a huge muscle movement. The size of the motor units is even big muscles like gastrocnemius, quadriceps group, hamstring group. These guys have very, very huge motor units because you really don't need to have a huge amount of control with those muscles. Fingers have much smaller motor units because you do a lot more fine motor action with your fingers than you do with your quadriceps or gastrocnemius. Here's another really cool fact. Are you ready for this? All muscle fibers in a motor unit are the same flavor. So if these are quick twitch muscles, muscle fibers, all of them are quick twitch muscle fibers. The motor unit, this is so cool. That's somatic motor neuron when you were a baby and these were little baby muscle cells. That's somatic motor neuron said, hey guys, if you're going to be on my team then you need to be my kind of muscle fiber. And so the somatic motor neuron reached out and started making contact with all these different myofibers and basically told them you have to be a quick twitch fiber because that's the way I roll. And they all became quick twitch fibers because their somatic motor neuron told them to. You can have different percentages of motor units, like you can have half your motor units quick twitch and half your motor units slow twitch, but all your myofibers in one motor unit are the same. Now, can you imagine how you can actually take your, the distribution of what kinds of motor units are found in the different muscles, that's going to be how your muscle overall is going to react. So that, let's see if there's anything else. Yeah, yeah, yeah, yeah. Okay. Now let's talk about generating massive contraction forces.