Motor Unit and Neuromuscular Junction

by Jason Amores Sumpter
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a motor unit is composed of a single motor neuron and the muscle fibers that it controls. The connection between the motor neuron and the muscle fibers is known as the neuromuscular junction. It's basically a synapse between neuron and a muscle. And here in this image you can see an example of a motor unit. Here we have our motor neuron. This is our neuromuscular junction right here inside. You can see all of these little myo filaments, and this whole thing here is a muscle fiber. Now, the muscle fibers of a motor unit are going to contract as a group. The nerve is going to release a Seattle coleene Lin. An action potential comes and this is going to stimulate muscle contraction. And the way that works is basically a seal Colin will bind to receptors on the other side of the Neuromuscular junction. Thes are called nicotine IQ receptors, in case you're curious, and this is gonna lead to deep polarization through excited Torrey post synaptic potentials. And that is going to cause an action potential that will actually travel into these indentations in the membrane called trans verse to Buell's. And that's gonna pull these action potentials into an area known as the Sarka plasmid. Ridiculous. Um, and this is basically a special type of smooth, smooth and a plasma critic Ulan that's found in my oocytes and the action potential will travel down these trans verse tubules and cause the sarka plasmid ridiculous, um, to release calcium. That's how this calcium is gonna get in there to bind to the troponin caused the trope Miocene to move out of the way. Uh, for the myson fill our heads to bind to the acting filaments. Now, after this is done, the calcium has to be pumped back into the SAARC. Plasvic ridiculous. Um because, you know, you need to be able Thio essentially make these discreet contractions, right? The nerves, they're gonna be sending discrete signals. And so we need to be able to have discrete muscle contractions. We also don't want to have permanent, uh, you know, contraction, permanent tension. Now, here you can see you know, an example of that action potential moving down this trans verse tube, you'll or T tube you'll as it's sometimes called, and this is going to lead to calcium release that will lead to contraction. You can see here. So with that, let's go ahead and turn the page