It’s a special day - we’re doing a kinesiology video, and ohhh boy that sports medicine degree
is finally about to pay off.
So!
There are over 600 or so muscles in the human body, and they’re a colossal pain in the
butt to memorize.
And really, the names and locations are just one layer of overall anatomy.
If the purpose of this big ol squishy sack of eat flesh is to move us through the world
and support literally every other system in your body, then we have to go deeper.
So in this video we’re going over the four concepts you’re gonna come across when you
*pop* open that anatomy book and flip to the musculoskeletal system.
Just the quickest of background - this is a skeletal muscle, one of the three types
of muscle in your body.
In order to actually move anything, it needs to attach to your skeleton via tendons.
One of those general areas is called the origin while the other is the insertion.
But, while it would make things simpler, we can’t just call them like the distal tendon
or proximal tendon because we actually label them based off of motion, not location.
In general, when the muscle contracts, the insertion moves towards the origin.
Let’s check out an example.
This dude here is the sternocleidomastoid, or the SCM, one of your neck muscles.
Named so because it hooks in at two spots: here at the sternum and a bit of the clavicle,
and here at the mastoid process of your skull.
So to figure out which one is the origin or insertion, we take a look at the action, which
isn’t as straightforward as you might think.
Here’s my advice - when you’re learning muscle actions, actually /do/ the motion.
Feel your muscle contract so you can figure out what that motion is and build a mental
picture of that motion.
The description of the action for my example muscle, the sternocleidomastoid is embarrassingly
drawn out, ready - when it acts unilaterally: contralateral cervical rotation and ipsilateral
cervical flexion, and bilaterally, cervical flexion, elevation of sternum and assistance
in forced inhalation.
And all of that just says you have two SCMs, so if you contract both of them, you flex
your neck but if you contract only one, you’ll end up rotating your neck as well.
Again, perform the actions, avoid memorizing sentences.
Or not, do you
Either way, in both cases, the skull moves towards the chest, so we label the mastoid
process as the insertion and that part of the chest as the origin.
Now, the sternocleidomastoid is pretty straightforward since it’s a super simple shape, but the
same rule applies for funky shaped muscles like the chest.
The pectoralis major, aka the Terry Crews, has a super wide origin that touches the sternum,
ribs, clavicle, and some connective tissue, but it’s insertion is a spot on the humerus.
And since the muscle’s actions bring the humerus either forward or towards the body,
its origin is that big chunk of medial tissue and its insertion is on the arm.
It might seem like there are a ton of intricacies to memorize with muscles, but for the most
part, if you know origins and insertions, you can figure out actions super easily and
the other way around.
Cool - the last concept that you’ll usually memorize when you do this lesson is innervation,
some nerve has to be stimulated to get that muscle to fire, and that nerve is the innervation.
And you can think about innervation in two main ways: you can either write the muscle
and nerve on a flash card and brute force memorize it, or just picture what group of
muscles that nerve matches up with.
Example - oculomotor nerve, one of those cranial nerves, innervates /a bunch/ of muscles that
move the eye.
Again, BRILLIANT example of anatomists being terrible namers.
So why should you care?
I mean once you got the names of the muscle bellies you should be golden, right?
Well dude, if you ever want to get into physical therapy, sports med, or even do some of these
therapies on yourself as a layperson, you end up using these Is and Os.
In everything from stretching to exercise, having a good foundation in some pretty precise
anatomy helps you out.
And having them just available in your brain bucket at a moment’s notice saves you a
lot of time looking stuff up.
And if you want to keep learning about the human body, then get over to that subscribe
button, like the video, comment your favorite muscle to say.
Have fun, be good, and I’ll see you next time.