Ninja Nerd · Transcript · · Updated
Musculoskeletal System | Muscle Structure and Function – Transcript
Video by Ninja Nerd · Watch the original on YouTube
Summary
AI-generated from the transcript. Verify details against the source video.
- Muscle tissue possesses four primary characteristics: excitability, contractility, extensibility, and elasticity.
- Skeletal muscle macroscopic structure includes the epimysium covering the muscle belly, perimysium surrounding fascicles, and endomysium surrounding muscle fibers.
- Muscles connect to bones either directly through the epimysium fusing with the periosteum or perichondrium, or indirectly through tendons and aponeuroses.
Key moments
Use this video with Pro
Reading, copying and transcript downloads are free. Create saved AI results for this video with a signed-in Pro account ($4.99/month).
Transcript
Search ignores accents. All transcript text stays visible.
all right Ninja nerds in this video today we are going to talk about the structure of skeletal muscle all right so first off before we start even getting into this diagram I want to talk a little bit about muscle so what are some of the characteristics of muscles so what I want you guys to remember uh with muscles is that there are four characteristics that make muscle tissue a little bit different from other tissues so for example one of those four characteristics so if we were to go here
in order one two three four the first thing about muscle that's really really spe special about is that it's excitable so it's one of the few tissue cells this in neural tissue that it's excitable so what do I mean by excitable let's say here I have just an actual muscle cell here's our muscle cell okay and then serving it is
some going to be some type of motor neur okay so here's our actual motor neuron this motor neuron is actually going to be responsible for stimulating this muscle cell how by releasing specific chemicals that we'll talk about more detail at the neuromuscular Junction they release out neurotransmitters for example in this case acetylcholine and what does this acetylcholine do it stimulates this muscle cell and what does this muscle cell in response to
that do it generates a change in membrane potential so it under goes what's called an Inplay potential and an action potential right so that's one thing about muscles as they're very excitable so they can respond to some type of stimulus usually a neural stimulus and they change their membrane potential in response to that another thing about that is when their membrane potential changes and they develop what's called an action potential that action
potential can be propagated along the actual muscle cell membrane and eventually trigger this muscle cell to shorten what does that mean whenever it can shorten for ibly due to frequent or adequate amount of stimulation that's called contractility so muscles also have contractility so they're contractile so one thing about muscles is that they have the ability to be excited so they can be stimulated by some neural stimulus in response to that
they can develop a membrane potential that membrane potential can then cause this muscle cell to shorten forcibly and when it does that due to adequate stimulation it can contract so it's contractile you know what else is really cool about muscle it has the ability to be stretched appropriately so you don't want to be able to stretch a muscle too much but it does have the ability to stretch Beyond its normal resting length so for example if I have a muscle here
let's say here's a muscle okay here's this muscle and this is at its resting length Okay this is at rest what I'm going to do is I'm going to stretch this muscle muscle so what would that do to this muscle it's going to allow for this muscle to be a little bit longer to be stretched Beyond its normal capabilities so this ability to stretch the muscles so this is rest and
this is stretched so the ability to stretch this muscle Beyond its normal resting Point allows for the muscle to be very distensible or extensible okay so we can use the word distensibility or extensibility okay so it's extensible just meaning stretchable okay another characteristics
of muscle tissue is the fact that it's elastic though too okay so it's also elastic and we'll talk about that when we talk about these connective tissue coverings so it has elasticity what is elasticity elasticity is for example we can say two different types of definitions one of them is whenever you try to stretch a muscle or any type of tissue let's just say any type of tissue for right now I stretch that when I stretch it it resists that desire to
want to stretch it always wants to recoil and go back to the smallest size possible so when you think about that me trying to stretch something and it's resisting it that's elasticity that's also a one of the characteristics of muscle tissue okay so these are some of the muscle characteristics okay now we're going to go over a lot of these different function of these actual muscle Muses for example we'll go over contraction with the
neuromuscular Junction and the excitation contraction coupling but just for right now what are four main functions of muscle if we were to just for right now go over four main functions of muscle just overall concept of it the four major functions that Encompass our muscles you know basically their function is going to be one is the ability to produce Locomotion what is
that mean you know if I want to be able to move my arm up it depends upon the muscles Contracting and pulling all my skeletal bones so because of that it's responsible for moving the skeleton or producing local motion so I'm just going to put producing movement producing movement of our skeleton so local motion another thing for me to be able to while I'm standing to maintain this posture okay or stability my body
position to maintain my posture against gravity because gravity is trying to push me down in order for me to able to maintain my posture and stand up straight and have normal body position I have to have those muscles there that are stabilizing that okay so because of that we also need the muscles to help us with our posture and stabilization right so helps to maintain our posture another thing is it wraps around
many different types of joints so because it's wrapping around joints joints are naturally stable on their own right because usually bones are connected with ligaments and other different types of structures right connective tissue structures but muscles help to stabilize those joints even more so another function of muscles is they stabilize a lot of our body's joints and another thing they help with temperature okay they so they help to be able to produce
or generate heat you can think about that I like to think about that just in general muscles are constantly whenever we actually undergo cellular respiration one of the byproducts of cellular respiration is heat production also I like to think about if you're really really cold what does your body try to do to be able to compensate for that cold it Shivers whenever you shiver the contractions aren aren't complete contractions so those quivering contractions help to be able to generate some heat okay so that's one of the
functions also of muscle so just a real quick recap just remember the general characteristics of muscle that it's excitable so it can receive a neural stimulus and it can respond by having a membrane potential if that membrane potential is adequate enough enough to produce an action potential the muscle can shorten forcibly which is called contractility on top of that it can be stretched Beyond its normal resting length right and that's because it's extensible okay so you can think about sometimes Ecentric contractions we'll
talk about that later elasticity is it has the ability to be stretched right but I should actually rephrase that specifically elasticity is once you want to reduce stretch you don't want you want to resist the change in the stretch it wants to recoil and assume the small size possible and also that functions it likes to produce Locomotion maintain posture and body position against anti you know anti-gravity effects helps to stabilize certain types of muscle joints think about the rotator cuff the rotator
cuff is a very good stabilizer of the actual shoulder joint the supinatus infraspinatus terus minor and subscapularis you can remember sits okay and it's also responsible for being able to generate heat to maintain certain types of body temperature for example when we're really cold we shiver to generate some heat okay so that's that now what I want to do is I want to zoom in on the actual overall macroscopic structure of the skeleton muscle and then we'll work our way down from
macroscopic to microscopic okay so let's do that so here we have a big old skeletal muscle so for example this is the femur so let's just say it's one of the actual quadriceps muscles right one of the actual muscles there coming off of the actual femur and what this muscle is going to do what we're going to do is we're going to take this slice it in half and we're going to look at it in this view so for example ex Le this is the whole muscle belly all I'm doing is I'm cutting this piece and opening up so we can see what it looks like inside of
it okay so I'm making this transverse cut and I'm flipping it over now when I do that you have to realize something there's actually a nice little connective tissue covering right over this muscle belly you see all this right here we actually peeled it back for you guys to see so we peeled this little part here back so if you guys can see right here this little connective tissue structure it's actually peeling we're peeling it back from this actual muscle
belly so this whole thing in here is the muscle belly surrounding this muscle belly is a little connective tissue covering right there this connective tissue covering I'm going to come from the top here because this this whole thing here we're just peeling that piece back this is called the Epi mum okay this is called the epimysium now the epimysium is a dense fibrous let's actually write that down that'd be good to know it's a dense
fibrous irregular I'm going to put IR connective tissue okay so it's very very tough they also call it you know your white fibrous tissue right so it's a very very tough connective tissue so that's going to be one of the connective tissues so this is actually going to be dense fibrous irregular connective tissue and again it's actually going to be actually uh connected right onto the actual large muscle belly
all right that's one part and also we'll talk about this in a second that this actual epimysium in certain types of situations very not as common as tendons and we'll talk about that it can actually fuse to the periosteum of the bone and form like direct fleshy attachments with the bone we'll talk about that in a little bit though all right so now what I did is okay so we have the epimysium right the connective tissue covering right around this whole muscle belly a section of that muscle
belly inside of that muscle belly you see a whole bunch of bundles of muscle fibers so you see this bundle right here this is a bundle consisting of muscle fibers this is a bundle consisting of muscle fibers and this is a bundle bundle bundle bundle these bundles of muscle fibers are called fices okay so this bundle right here of muscle fibers this bundle is called a fasle so a fasle is a
bundle of muscle fibers okay now surrounding the faasle is another connective tissue layer so for example we just blew up one of the faes we blew up one of these fases and if you see there's a nice little black connective tissue covering around that fasle right there we peeled that piece back again for you so you see that little connective tissue covering around this and we peeled a piece back
around this fasle this part right here this connective tissue is actually called the parium okay it's called the Perry mum now the parium just like the epimysium they're actually continuous with one another and that's going to be a very important I'll explain why that's important in a second but the parium is a nice dense fibrous irregular
connective tissue just like thatum okay so it's a nice dense fibrous irregular I'm going to put IR connective tissue so really really cool stuff there all right and again what I said is that this actual parium the epimysium and this last one that we're going to talk about the endomysium are all continues
with one another all right so now this is a fasle this is a fasle fasle fasle fasle fasle fasle fasle the whole thing is a muscle belly okay what I'm going to do now is I'm going to take out of this fasle I'm going to pull one of these structures out this tube you see this tube that I pulled out this is a muscle fiber okay so this one right here is
specifically called a muscle fiber now sometimes you might hear the word muscle fiber and muscle cell used interchangeably because they are the same thing a muscle fiber and a muscle cell is the same exact thing okay this muscle fiber so you can see that there's tons and tons of muscle fibers within this bundle of these structures bundle of muscle fibers in
here it's called a fasle right an individual structure here is a muscle fiber or a muscle cell now there is another connective tissue covering surrounding this actual muscle fiber another connective tissue but it's not as tough of a connective tissue there's a connective tissue this black connective tissue we peeled a little bit of back it might be hard to see but there's another little connective tissue that we peel back surrounding this muscle fiber and that is called the