Alright, I want to talk about the three muscle types. Skeletal, cardiac, and smooth. And how to identify them both by their features and know a little bit about their structure and function. Skeletal muscle you'll learn a lot about in a couple of videos.
chapters all the muscles that you think of that are named like your biceps your abdominals all of those are skeletal muscles anyone that moves your skeleton um they are all voluntary because you decide now you might have reflexes that allow some involuntary movements like when you pull something back if there's something hot or your patella tendon reflex if they use the hammer on your knee and your leg kicks out. But in general those muscles can be controlled voluntarily so we consider them voluntary. Also skeletal muscles are striated.
These striations you'll learn more about the structure of the striations that are made up of these actin and myosin and other accessory proteins and very regulated and regular patterns that I'll... form these striations. Skeletal muscle in general are in these really consistent thickness lengths.
The skeletal cells themselves are called muscle fibers. They are multi-nucleated and you see these nuclei that are often elongated along the muscle cells. So that's how you recognize skeletal muscle.
Cardiac muscle have some similarities visually so they are both striated. and they both have nuclei. The difference is the nuclei aren't as thin and elongated, and there's only one nucleus per cell.
Sometimes it's hard to tell where the separations of the cardiac muscle cells are, but what you can see is you should usually, for cardiac muscle tissue, see these thickening parts near the striations. These are called interpolated discs. These are going to be points that are going to be really important for heart function because they will allow ions to flow through. So if one cardiac muscle cell is stimulated to contract, it will very quickly be able to tell the cells that are connected through these intercalated discs so they can contract also. It allows your heart to contract very consistently and quickly.
So if you see these thicker red lines that are sort of vertically through, those are intercalated discs. That's a good hint. that their cardiac muscle, they also are more branched, so they're not going to be as consistent in width. The nuclei tend to be a little bit more round versus the skeletal muscle.
But they are also striated just like cardiac, so you have to look for the differences to be able to tell. They are involuntary muscles, which obviously you can't control how fast your heart is beating. Third type is the smooth muscle.
It's also involuntary, just like cardiac, so skeletal is the only voluntary muscle. However, what makes... makes it unique, it's not striated.
So the cardiac and skeletal have the very consistent organizations of the actinomycin to form these striations. Smooth muscle does not. It does have those same motor, does have motor proteins that are controlling contraction, but their structure is different. So you don't see striations.
You will see a nuclei in each cell. And basically, the only thing I will say about smooth muscle, if you know it's a muscle and you don't see striations, you know it's a smooth muscle. muscle.
Sometimes this tissue might look like some other tissues so you either need to use the description, the location, or something or some reference to be able to identify smooth muscle versus some types of connective tissue that it might look like. But of the three types of muscle tissue it should be pretty obvious what's smooth.