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all right Ninja nerds in this video
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today we are going to talk about the
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structure of skeletal muscle all right
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so first off before we start even
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getting into this diagram I want to talk
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a little bit about muscle so what are
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some of the characteristics of muscles
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so what I want you guys to remember uh
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with muscles is that there are four
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characteristics that make muscle tissue
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a little bit different from other
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tissues so for
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example one of those four
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characteristics so if we were to go here
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in order
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one two three four the first thing about
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muscle that's really really spe special
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about is that it's excitable so it's one
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of the few tissue cells this in neural
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tissue that it's excitable so what do I
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mean by excitable let's say here I have
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just an actual muscle cell here's our
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muscle cell okay and then serving it is
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some going to be some type of motor neur
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okay so here's our actual motor neuron
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this motor neuron is actually going to
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be responsible for stimulating this
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muscle cell how by releasing specific
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chemicals that we'll talk about more
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detail at the neuromuscular Junction
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they release out neurotransmitters for
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example in this case acetylcholine and
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what does this acetylcholine do it
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stimulates this muscle cell and what
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does this muscle cell in response to
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that do it generates a change in
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membrane
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potential so it under goes what's called
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an Inplay potential and an action
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potential right so that's one thing
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about muscles as they're very excitable
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so they can respond to some type of
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stimulus usually a neural stimulus and
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they change their membrane potential in
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response to that another thing about
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that is when their membrane potential
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changes and they develop what's called
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an action potential that action
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potential can be propagated along the
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actual muscle cell membrane and
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eventually trigger this muscle cell to
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shorten what does that mean whenever it
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can shorten for ibly due to frequent or
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adequate amount of stimulation that's
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called contractility so muscles also
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have
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contractility so they're
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contractile so one thing about muscles
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is that they have the ability to be
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excited so they can be stimulated by
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some neural stimulus in response to that
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they can develop a membrane potential
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that membrane potential can then cause
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this muscle cell to shorten forcibly and
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when it does that due to adequate
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stimulation it can contract so it's
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contractile you know what else is really
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cool about muscle it has the ability to
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be stretched appropriately so you don't
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want to be able to stretch a muscle too
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much but it does have the ability to
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stretch Beyond its normal resting length
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so for example if I have a muscle here
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let's say here's a
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muscle okay here's this muscle and this
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is at its resting length Okay this is at
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rest what I'm going to do is I'm going
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to stretch this muscle muscle so what
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would that do to this muscle it's going
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to allow for this muscle to be a little
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bit longer to be stretched Beyond its
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normal capabilities so this ability to
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stretch the muscles so this is rest and
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this is
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stretched so the ability to stretch this
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muscle Beyond its normal resting Point
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allows for the muscle to be very
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distensible or extensible okay so we can
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use the word distensibility or
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extensibility okay so it's extensible
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just meaning
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stretchable okay another characteristics
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of muscle tissue is the fact that it's
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elastic though too okay so it's also
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elastic and we'll talk about that when
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we talk about these connective tissue
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coverings so it has elasticity what is
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elasticity elasticity is for example we
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can say two different types of
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definitions one of them is whenever you
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try to stretch a muscle or any type of
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tissue let's just say any type of tissue
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for right now I stretch that when I
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stretch it it resists that desire to
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want to stretch it always wants to
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recoil and go back to the smallest size
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possible so when you think about that me
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trying to stretch something and it's
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resisting it that's elasticity that's
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also a one of the characteristics of
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muscle tissue okay so these are some of
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the muscle
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characteristics
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okay now we're going to go
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over a lot of these different function
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of these actual muscle Muses for example
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we'll go over contraction with the
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neuromuscular Junction and the
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excitation contraction coupling but just
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for right now what are four main
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functions of muscle if we were to just
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for right now go over four main
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functions of muscle just
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overall concept of it the four major
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functions that
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Encompass our muscles you know basically
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their function is going to be one is the
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ability to produce Locomotion what is
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that mean you know if I want to be able
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to move my arm up it depends upon the
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muscles Contracting and pulling all my
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skeletal bones so because of that it's
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responsible for moving the skeleton or
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producing local motion so I'm just going
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to put producing
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movement
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producing movement of our skeleton so
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local motion another thing for me to be
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able to while I'm standing to maintain
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this posture okay or stability my body
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position to maintain my posture against
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gravity because gravity is trying to
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push me down in order for me to able to
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maintain my posture and stand up
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straight and have normal body position I
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have to have those muscles there that
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are stabilizing that okay so because of
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that we also need the muscles to help us
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with our
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posture and stabilization right so helps
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to maintain our
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posture another thing is it wraps around
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many different types of joints so
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because it's wrapping around joints
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joints are naturally stable on their own
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right because usually bones are
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connected with ligaments and other
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different types of structures right
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connective tissue structures but muscles
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help to stabilize those joints even more
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so another function of muscles is they
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stabilize a lot of our body's
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joints and another
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thing they help with temperature okay
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they so they help to be able to produce
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or
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generate heat you can think about that I
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like to think about that just in general
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muscles are constantly whenever we
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actually undergo cellular respiration
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one of the byproducts of cellular
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respiration is heat production also I
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like to think about if you're really
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really cold what does your body try to
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do to be able to compensate for that
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cold it Shivers whenever you shiver the
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contractions aren aren't complete
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contractions so those quivering
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contractions help to be able to generate
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some heat okay so that's one of the
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functions also of muscle so just a real
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quick recap just remember the general
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characteristics of muscle that it's
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excitable so it can receive a neural
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stimulus and it can respond by having a
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membrane potential if that membrane
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potential is adequate enough enough to
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produce an action potential the muscle
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can shorten forcibly which is called
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contractility on top of that it can be
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stretched Beyond its normal resting
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length right and that's because it's
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extensible okay so you can think about
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sometimes Ecentric contractions we'll
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talk about that later elasticity is it
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has the ability to be stretched right
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but I should actually rephrase that
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specifically elasticity is once you want
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to reduce stretch you don't want you
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want to resist the change in the stretch
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it wants to recoil and assume the small
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size possible and also that functions it
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likes to produce Locomotion maintain
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posture and body position against anti
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you know anti-gravity effects helps to
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stabilize certain types of muscle joints
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think about the rotator cuff the rotator
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cuff is a very good stabilizer of the
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actual shoulder joint the supinatus
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infraspinatus terus minor and
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subscapularis you can remember sits okay
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and it's also responsible for being able
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to generate heat to maintain certain
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types of body temperature for example
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when we're really cold we shiver to
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generate some heat okay so that's that
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now what I want to do is I want to zoom
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in on the actual overall macroscopic
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structure of the skeleton muscle and
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then we'll work our way down from
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macroscopic to microscopic okay so let's
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do that so here we have a big old
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skeletal muscle so for example this is
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the femur so let's just say it's one of
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the actual quadriceps muscles right one
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of the actual muscles there coming off
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of the actual femur and what this muscle
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is going to do what we're going to do is
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we're going to take this slice it in
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half and we're going to look at it in
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this view so for example ex Le this is
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the whole muscle belly all I'm doing is
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I'm cutting this piece and opening up so
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we can see what it looks like inside of
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it okay so I'm making this transverse
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cut and I'm flipping it over now when I
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do that you have to realize something
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there's actually a nice little
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connective tissue covering right over
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this muscle belly you see all this right
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here we actually peeled it back for you
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guys to see so we peeled this little
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part here back so if you guys can see
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right here this little connective tissue
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structure it's actually peeling we're
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peeling it back from this actual muscle
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belly so this whole thing in here is the
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muscle belly surrounding this muscle
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belly is a little connective tissue
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covering right there this connective
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tissue covering I'm going to come from
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the top here because this this whole
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thing here we're just peeling that piece
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back this is called the
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Epi
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mum okay this is called the epimysium
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now the epimysium is a dense fibrous
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let's actually write that down that'd be
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good to know it's a dense
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fibrous irregular I'm going to put IR
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connective
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tissue okay so it's very very tough they
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also call it you know your white fibrous
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tissue right so it's a very very tough
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connective tissue so that's going to be
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one of the connective tissues so this is
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actually going to be dense fibrous
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irregular connective tissue and again
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it's actually going to be actually uh
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connected right onto the actual large
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muscle belly
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all right that's one part and also we'll
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talk about this in a second that this
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actual epimysium in certain types of
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situations very not as common as tendons
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and we'll talk about that it can
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actually fuse to the periosteum of the
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bone and form like direct fleshy
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attachments with the bone we'll talk
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about that in a little bit though all
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right so now what I did is okay so we
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have the epimysium right the connective
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tissue covering right around this whole
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muscle belly a section of that muscle
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belly inside of that muscle belly you
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see a whole bunch of bundles of muscle
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fibers so you see this bundle right here
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this is a bundle consisting of muscle
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fibers this is a bundle consisting of
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muscle fibers and this is a bundle
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bundle bundle bundle these bundles of
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muscle fibers are called fices okay so
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this bundle right here of muscle
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fibers this bundle is called a
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fasle so a fasle is a
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bundle of
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muscle
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fibers okay now surrounding the
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faasle is another connective tissue
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layer so for example we just blew up one
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of the faes we blew up one of these
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fases and if you see there's a nice
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little black connective tissue covering
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around that fasle right there we peeled
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that piece back again for you so you see
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that little connective tissue covering
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around this and we peeled a piece back
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around this fasle this part right here
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this connective
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tissue is actually called the parium
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okay it's called the Perry
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mum now the parium just like the
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epimysium they're actually continuous
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with one another and that's going to be
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a very important I'll explain why that's
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important in a second but the parium is
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a nice dense fibrous irregular
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connective tissue just like thatum okay
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so it's a nice
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dense
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fibrous irregular I'm going to put IR
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connective
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tissue so really really cool stuff there
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all right and again what I said is that
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this actual parium the epimysium and
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this last one that we're going to talk
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about the endomysium are all continues
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with one another all right so now this
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is a fasle this is a fasle fasle fasle
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fasle fasle fasle fasle the whole thing
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is a muscle belly okay what I'm going to
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do now is I'm going to take out of this
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fasle I'm going to pull one of these
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structures out this tube you see this
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tube that I pulled out this is a muscle
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fiber okay so this one right here is
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specifically called a muscle
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fiber now sometimes you might hear the
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word muscle fiber and muscle cell used
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interchangeably because they are the
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same thing a muscle fiber and a muscle
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cell is the same exact
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thing okay this muscle fiber so you can
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see that there's tons and tons of muscle
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fibers within this bundle of these
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structures bundle of muscle fibers in
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here it's called a fasle right an
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individual structure here is a muscle
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fiber or a muscle cell now there is
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another connective tissue covering
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surrounding this actual muscle fiber
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another connective tissue but it's not
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as tough of a connective tissue there's
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a connective tissue this black
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connective tissue we peeled a little bit
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of back it might be hard to see but
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there's another little connective tissue
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that we peel back surrounding this
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muscle fiber and that is called the
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indom myum
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Endo myum now the endomysium is an
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areolar connective tissue so it's a it's
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not as tough it's not as a it's not as
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tough and actual resistant and resilient
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as compared to the dense fibrous
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irregular connective tissue because you
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know aola connective tissue it has a
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little less collagen as compared to this
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dense fibrous irregular connective
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tissue okay we'll talk about this next
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thing in another video the next video
00:13:51
where we discuss the neuromuscular
00:13:53
Junction but the endomysium is covering
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this muscle fiber there's what's called
00:13:59
called the plasma membrane and the
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plasma membrane is actually covered by
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this endomysium so there is a plasma
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membrane it's here in red the muscle
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fiber is surrounded by a structure
00:14:10
called the
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sarcolemma and we will talk about this
00:14:14
in the neuromuscular Junction video but
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again don't get this confused with the
00:14:18
endomysium the endomysium is wrapping
00:14:21
over the sarcolemma okay so this is
00:14:23
actually the plasma membrane so this is
00:14:25
your phospholipid by layer okay so don't
00:14:28
get that confused used with the
00:14:30
endomysium okay so the muscle fiber is
00:14:33
surrounded let me actually make that
00:14:34
clear it's surrounded by this sarcolemma
00:14:40
surrounded by this
00:14:44
sarcolemma all right so it's surrounded
00:14:46
by the CC Lima which is this plasma
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membrane which is again a phospholipid
00:14:50
by
00:14:52
layer okay now we have all of these
00:14:56
actual connective tissue coverings right
00:14:58
and again to recap surrounding the
00:15:00
muscle belly is the epy which is dense
00:15:02
fibrous irregular connective tissue in
00:15:04
this whole muscle belly you have
00:15:06
multiple fases and these fases are just
00:15:09
bundles of muscle fibers each individual
00:15:13
faasle is covered by another connective
00:15:15
tissue and that connective tissue is the
00:15:18
same connective tissue as epimysium it's
00:15:20
dense fibrous irregular connective
00:15:22
tissue but we call it parium okay
00:15:25
because it's covering these fases then
00:15:28
in each individ idual fasle is many many
00:15:31
many muscle fibers or muscle cells these
00:15:35
muscle fibers each individual one is
00:15:38
covered by another connective tissue
00:15:40
which is an AOL connective tissue called
00:15:42
the
00:15:43
endomysium but un surrounding this you
00:15:47
know you have the endomysium surrounding
00:15:49
this muscle fiber this muscle fiber or
00:15:51
cell has a membrane called the
00:15:54
sarcolemma it's the plasma membran a
00:15:56
phospholipid bilayer that's underneath
00:15:59
the
00:15:59
endomysium all right now I told you that
00:16:02
all of these structures the endomysium
00:16:04
the parium and the epimysium are all con
00:16:07
continuous with one another and what I
00:16:10
mean by that
00:16:11
is you know how we have this actual
00:16:14
tendon here let's say this is the tendon
00:16:16
so here's a tendon connecting the muscle
00:16:18
what is a tendon by definition what is a
00:16:20
tendon so this right here is a tendon
00:16:23
but a
00:16:24
tendon is a ropik connective tissue rich
00:16:29
and rich in collagen so what does that
00:16:31
mean so what that means is that collagen
00:16:33
is very resilient right so it's very
00:16:36
resilient very tough so what this tendon
00:16:38
is doing is it's connecting the muscle
00:16:41
to the Bone now here's what's really
00:16:44
cool when this muscle fiber contracts so
00:16:47
let's say we take this individual muscle
00:16:49
fiber it contracts when it contracts it
00:16:53
pulls on the endomysium what did I tell
00:16:56
you all of these structures are
00:16:58
continuous so if this actual what this
00:17:01
muscle fiber contracts what does it do
00:17:03
it pulls on the endomysium it pulls on
00:17:05
the parium it pulls on the epimysium and
00:17:08
if that's the case then it's pulling on
00:17:10
all these connective tissue sheets what
00:17:12
is that going to do this can actually be
00:17:14
connected with a tendon and the tendon
00:17:16
is what's connecting the muscle to the
00:17:18
Bone so one more time if the muscle
00:17:21
fibers contract they pull on the
00:17:23
endomysium the parium and epimysium when
00:17:26
they pull on that they pull on the
00:17:28
tendon and if they pull on the tendon
00:17:30
what is that going to do to the Bone
00:17:31
it's going to move it so that is the
00:17:34
function of these actual connective
00:17:35
tissue sheets so again one more time
00:17:37
let's actually kind of follow it in like
00:17:38
a float pattern muscle
00:17:42
contracts so say that the muscle
00:17:44
fiber
00:17:46
contract what does that do to the
00:17:48
connective tissue sheaths all the
00:17:49
endomysium epimysium and parami the
00:17:52
connective tissue I'm going to put CT
00:17:55
sheaths are pulled on okay
00:18:02
when they're pulled on they're going to
00:18:04
pull on a result the tendons so they're
00:18:08
going to pull
00:18:09
on
00:18:11
tendons and when you pull on the tendons
00:18:14
what is that going to do the bone it's
00:18:15
going to pull on the bone and move the
00:18:17
bone and what's that going to produce
00:18:18
Locomotion right so it's going to pull
00:18:21
or
00:18:23
move
00:18:25
bone and obviously depending upon the
00:18:28
type of muscle it also depends upon
00:18:30
what's called insertion and origin what
00:18:32
is what is meant by insertion and origin
00:18:35
so let's say I take for example simple
00:18:38
muscle let's say I take the M okay let's
00:18:40
say I take the m so here I have my M
00:18:43
muscle now just to be really simplistic
00:18:45
here there's two bones that the m is
00:18:47
generally connecting to let's say here's
00:18:49
one bone and let's say here's the other
00:18:51
bone okay just a crew
00:18:53
diagram then what I'm going to do is I'm
00:18:55
going to link this muscle up between
00:18:58
these two bones cuz that's really what's
00:19:00
happening this muscle is being you know
00:19:02
a connected a connection between these
00:19:04
bones and then what's happening is I'm
00:19:07
having a tendonous connection let's show
00:19:09
that here in this blue so let's say I
00:19:12
have a tendonous connection here and a
00:19:14
tendonous connection right here let's
00:19:17
say this bone that this mass of muscle
00:19:19
is connected to is the zygomatic bone so
00:19:21
this one up here is the
00:19:23
zygo Matic
00:19:26
bone and this bone down here is the
00:19:28
mandible so let's say this is the
00:19:31
mandible when the muscle is Contracting
00:19:33
and again what is this muscle here
00:19:35
called this muscle is called the we're
00:19:36
just taking the masser muscle as an
00:19:38
example it's one of the muscles that
00:19:40
helps in chewing what's called
00:19:42
mastication what happens is we have to
00:19:44
determine what's the insertion and
00:19:46
what's the origin I'm going to write it
00:19:47
down for right now and I'm going to
00:19:49
explain why
00:19:51
okay so if that's the case I'm gonna
00:19:54
explain to you it's GNA make more sense
00:19:56
after I get it all done the mandible is
00:19:58
actually moving that's the function of
00:20:00
the m so the M helps to pull the
00:20:02
mandible up Elevate the mandible so I
00:20:04
think about in this position and I'm
00:20:05
going to elevate it that's the job of
00:20:08
the masser so it's moving the mandible
00:20:10
up so if that's the case this is the one
00:20:12
that's
00:20:14
moving nothing happened to my zygomatic
00:20:16
bone I didn't move that bone it stayed
00:20:18
still so it stayed still it's not
00:20:22
moving if that's the case then what
00:20:26
happens is when a muscle contracts the
00:20:28
part of the bone that's not moving is
00:20:31
referred to as
00:20:32
the origin okay and then the part that's
00:20:37
actually moving is referred to as the
00:20:42
insertion what happens is when a muscle
00:20:44
contracts it moves from insertion to
00:20:46
origin but again what is connecting this
00:20:49
muscle to the bones the tendons but you
00:20:53
know that's not all that's connecting
00:20:54
them besides
00:20:56
tendons you have other examples of these
00:20:59
connective tissue sheaths in your body
00:21:01
for example on the top of the head first
00:21:03
one that you I can think of or within
00:21:04
the actual abdomen there sheets all
00:21:07
right they're sheets of actual
00:21:08
connective tissue so a tendon imagine a
00:21:11
tendon is like a
00:21:12
rope it's a rope like connection between
00:21:15
the muscle and the bone so this would be
00:21:16
an example of a
00:21:17
tendon another one is like this imagine
00:21:22
a sheet so imagine actual sheet this is
00:21:25
an example of an Appo
00:21:29
Neurosis so an aerosis is a sheetlike
00:21:32
connective tissue that's connecting
00:21:35
muscle to Bone a tendon is a cord okay
00:21:39
or a ropeik connective tissue that's
00:21:41
connecting muscle to
00:21:43
Bone all right so now again what did we
00:21:45
cover here we said all of these
00:21:48
connective tissue sheaths are important
00:21:50
because when a muscle fiber contracts it
00:21:52
pulls on the connective tissue sheets
00:21:54
Which pull on the tendons Which pull or
00:21:56
move the bone depending upon on what the
00:21:59
tendons are connected to determines the
00:22:01
actual direction right so for example if
00:22:03
we say the tendons are connected to the
00:22:05
mandible and they're also connected here
00:22:06
to the zygomatic bone right what's going
00:22:08
to happen well the mandible is not the
00:22:11
part that's actually it's the it's the
00:22:12
part that's actually moving so whenever
00:22:14
the muscle contracts it moves that bone
00:22:16
up that must be the
00:22:18
insertion this point where the tendon is
00:22:20
actually connecting is not moving okay
00:22:23
that point is not moving that's fixed so
00:22:25
that has to be the origin an insertion
00:22:27
always moves towards the
00:22:29
origin now another thing you know these
00:22:33
connective tissue sheaths they also
00:22:35
contribute to elasticity what do I mean
00:22:38
by elasticity again elasticity is that
00:22:41
ability to resist that change in the
00:22:44
actual stretch or deformation and the
00:22:47
reason why is because it's a dense
00:22:48
fibrous irregular connective tissue
00:22:50
they're not very good at allowing for
00:22:51
stretch all right so now you know these
00:22:54
connective tissue sheets you know what's
00:22:55
also really important with these
00:22:56
connective tissue sheets because it's
00:22:57
dense fibrous irregular connective
00:22:59
tissue those types of connective tissue
00:23:01
want to resist the stretch they
00:23:03
constantly want to be able to pull the
00:23:05
muscle and maintain its normal size they
00:23:07
don't like being stretched so because of
00:23:09
that they contribute to elasticity so
00:23:12
another function of these connective
00:23:13
tissue sheets you know again the
00:23:16
endomysium parium epom myum these
00:23:18
connective tissue
00:23:20
sheets are contributing
00:23:25
to elasticity
00:23:31
I say they they're contributing to
00:23:33
elasticity and that's really
00:23:35
important and another thing that
00:23:37
actually happens is you know these
00:23:39
actual dense fibrous irregular
00:23:40
connective tissue is decently
00:23:41
vascularized not superiorly vascularized
00:23:43
but it's enough vascularization so they
00:23:46
do have blood vessels that are running
00:23:47
through there and nerve fibers that are
00:23:49
running through these connective tissue
00:23:51
sheaths those three functions I want you
00:23:52
guys to remember for connected tissue
00:23:54
sheaths one when a muscle contracts the
00:23:57
muscles pull on the sheaths those pull
00:23:59
on the tendons Which pull or move the
00:24:01
bone second thing I want you to know
00:24:03
that they contribute to elasticity so
00:24:06
they want to prevent the actual or
00:24:07
resist the desire of the muscle to be
00:24:09
stretched they want it to recoil they
00:24:11
want to assume the smallest size
00:24:12
possible third thing I want you guys to
00:24:14
remember besides that is also that blood
00:24:17
vessels and nerve fibers are running
00:24:19
through these connective tissue sheaths
00:24:21
all right last thing and then we're
00:24:22
going to go into the
00:24:24
sarir another thing that's really
00:24:25
important is understanding how muscles
00:24:27
are connecting to Bone because muscles
00:24:29
can connect the bone in two ways okay
00:24:31
let's let's go over that quick
00:24:34
now okay so there's two ways in which
00:24:37
the muscle connects so how can these
00:24:38
muscles so
00:24:40
muscle to
00:24:43
Bone
00:24:45
connection two
00:24:47
ways one way is a direct
00:24:52
attachment okay the second way is
00:24:55
indirect
00:24:59
out of these this is less common this is
00:25:02
not as common so this is less
00:25:07
common and this is much much much more
00:25:11
common many of the ways that we are
00:25:14
actually connecting our bones to muscles
00:25:15
it's through indirect connections we've
00:25:17
already talked a little bit about them
00:25:19
the direct connection and simple to make
00:25:21
it the most simple as
00:25:23
possible all it is is is this this
00:25:27
connection from from the epy to the Bone
00:25:31
so when epimysium is fusing with the
00:25:33
bone specifically what structure of the
00:25:35
bone so epimysium is dense fibrous
00:25:37
irregular connective tissue there's
00:25:39
another connective tissue that's
00:25:42
actually clinging directly to the
00:25:44
Bone and this connective tissue that's
00:25:47
clinging directly to the bone is
00:25:49
actually called per oium so what happens
00:25:52
is whenever the
00:25:56
periostium is fusing
00:25:59
with the epim myum that is a direct
00:26:02
fleshy attachment another thing though
00:26:05
you know that that uh at the end of our
00:26:06
bones usually usually you have a
00:26:09
Highland cartilage Highland cartilage
00:26:11
that's actually you know right here and
00:26:13
then there's actually going to be this
00:26:14
actual dense fibrous irregular
00:26:16
connective tissue that's surrounding
00:26:17
that so if that's the case what's that
00:26:20
called that's called peric condum so you
00:26:23
have a per
00:26:25
oium or paric condum
00:26:29
any direct connection between the
00:26:31
epimysium and the periostium or the
00:26:34
parondi is a direct connection okay
00:26:38
that's a direct connection so let's
00:26:40
write that one down so any direct
00:26:42
connection Which is less common is going
00:26:45
to be
00:26:48
epimysium fusing with the per
00:26:54
oium or it's fusing with
00:26:56
the par
00:27:02
condum okay that is an example of a
00:27:05
direct or fleshy attachment not as
00:27:07
common the indirect ones are much much
00:27:10
more common I'll I'll give you two
00:27:11
reasons why these indirect connections
00:27:13
are mediated through tendons which we
00:27:15
already talked about and aerosis which
00:27:18
we already talked
00:27:20
about okay I want you guys to think
00:27:22
logically here about why tendons and
00:27:25
aerosis more commonly tendons are more
00:27:27
common for connection between muscle to
00:27:29
Bone all right first reason tendons are
00:27:32
much smaller okay so because tendons are
00:27:35
a lot smaller they're going to conserve
00:27:37
more space so that's one reason why the
00:27:40
indirect connections are better so one
00:27:41
reason why indirect connections are
00:27:43
better so let's say here we have
00:27:47
indirect uh connections or
00:27:50
attachments one reason why is it
00:27:53
conserves
00:27:54
space because tendons are much much
00:27:58
smaller than these having these direct
00:28:00
fleshy attachments that's one reason
00:28:02
simple
00:28:03
reason second reason a little bit
00:28:06
different the other reason is actually
00:28:08
because it's very resilient or
00:28:13
tough okay so that's one reason it's
00:28:16
very resilient what do I mean by that so
00:28:18
you know these tendons are actually
00:28:20
going to be uh undergoing a lot of uh
00:28:22
rubbing between the bone all right so
00:28:25
whenever the bones are actually moving
00:28:27
right so whenever the bones are moving
00:28:28
because of the skeletal muscles allowing
00:28:29
for them to contract those tendons might
00:28:31
actually have a little bit of friction
00:28:33
against the bones what happens is is if
00:28:36
that was fleshy connections those would
00:28:38
completely get fricked up all right they
00:28:40
would get destroyed in that kind of
00:28:41
situation so they're not very good in
00:28:43
that situation because tendons are a lot
00:28:45
of collagen connective tissue so it's if
00:28:47
a lot of collagen what does that mean if
00:28:49
there's a lot of collagen it's very very
00:28:50
tough very very resilient and it's able
00:28:52
to be able to allow for the bones to rub
00:28:54
up against it and not actually break
00:28:56
apart right so that's one reason so a
00:28:59
good thing for indirect connections is
00:29:00
that they're very small so they cons
00:29:02
serve a lot of space second reason is
00:29:04
that they can resist a lot of abrasion
00:29:06
and friction whenever the bones rub up
00:29:08
against it okay that's that's the second
00:29:10
reason so two reasons why is because
00:29:12
it's very resilient because of the
00:29:13
collagen connective tissue and because
00:29:15
of that it can undergo resistance
00:29:17
against abrasion whenever the bones are
00:29:18
rubbing up against it second reason is
00:29:21
they're small and they conserve
00:29:23
space all right so now what we're going
00:29:25
to do is we're going to take a look here
00:29:27
for a second this is our muscle fiber
00:29:29
our muscle cell right that was covered
00:29:31
with the endomysium and underneath the
00:29:32
endomysium was the plasma membrane which
00:29:34
is the
00:29:35
sarcolemma now that muscle cell consists
00:29:39
of thousands upon
00:29:41
thousands of these little structures
00:29:43
here what is this structure right here
00:29:45
called this structure right here is
00:29:47
called a myof
00:29:51
fibral okay a myofibril is consisting of
00:29:55
tons and tons of proteins now a myof
00:29:58
fibral again like I said you can have
00:30:00
hundreds to thousands of these myof
00:30:02
fibral within one muscle cell and also
00:30:04
these muscle cells you'll notice that
00:30:06
they have this blue structure around
00:30:07
them we'll talk about that in the
00:30:08
neuromuscular Junction video but that is
00:30:10
going to be super super important I'm
00:30:12
going to write it down for right now
00:30:13
it's called the
00:30:15
Sarco
00:30:17
plasmic
00:30:19
reticulum and it's a nice Factory of
00:30:22
calcium and we'll see why whenever we
00:30:24
talk about that with respect to the T
00:30:25
tubules also you notice that these
00:30:27
skeleton muscles are very cylindrical
00:30:29
okay so each skeletal muscle fiber is
00:30:31
very cylindrical and it's multinucleated
00:30:34
okay so again remember this for a
00:30:35
skeletal muscles I want you to remember
00:30:37
that they have a nice little
00:30:38
filamentous uh sarcoplasmic reticulum
00:30:41
which is kind of like a derivative of
00:30:42
the endoplasmic reticulum and it's a
00:30:44
calcium storage Factory it's going to
00:30:46
have a cylindrical shape and it's going
00:30:48
to be striated I should write that down
00:30:51
that's an important thing to write down
00:30:52
so another thing about these actual
00:30:53
muscle fibers or cells is that they're
00:30:55
striated
00:30:58
so what is meant by
00:31:00
striated it means that it takes on like
00:31:03
a striped appearance and that's what
00:31:06
we're going to look at in this situation
00:31:08
here this whole big beast that we're
00:31:10
having over here and you guys are
00:31:11
probably wondering about this big beast
00:31:13
over here is actually the functional and
00:31:15
structural unit of the muscle cell it's
00:31:18
actually called the ccir and that's what
00:31:20
we're going to talk about in the next
00:31:21
video all right so what we're going to
00:31:23
do in the next video guys is we're going
00:31:24
to go over a little bit more detail on
00:31:26
this actual a specific myof fibro
00:31:29
consisting of this sarcomeric structure
00:31:31
all right so I'll see you guys in the
00:31:33
next video in part two where we talk
00:31:35
about a little bit more about the actual
00:31:37
sarir
