hello anatomy friends it is dr alsup again and we are going to
talk about muscle attachments and their significance uh basically their functions
and there are a lot of terms we are going to work through together but having a running knowledge of
the this terminology will really help in some of our later conversations regarding specific muscles
so muscle attachment sites what i mean here is uh the sites or the locations that a muscle will
actually connect or attach to the bone so uh when i say the muscle to to really what i'm talking
about is the muscle tendon attaching to the bone and when a muscle contracts one of its attachments
usually remains fixed or in other words that bone doesn't move while the other
attachment site does move and it's typically pulled toward the immovable attachment site
with the more traditional terminology the immovable attachment side is referred to
as the origin so the the part that is going to be stationary or the site that'll be stationary
and these tend to be more proximally or superiorly placed whereas that movable part or
that movable attachment site is referred to as an insertion and these tend to be distal or inferior
but for some muscles uh sites can be movable depending on or excuse me for some muscles
um the the it can be dependent on the action as to which site will be movable and which side will not
and so that really would change the meaning or the main meaning of the origin insertion so there's
been a movement in anatomy textbooks away from the terms of origin and insertion and more towards the
more descriptive proximal and distal attachments so when we're talking about the individual muscles
and their attachment sites you will typically in my area see on the slides more proximal and distal
but change is slow going and many people like this person who happens to be talking
right now learned origin and assertions so it's hard to to kind of teach an old dog new
trick so you will likely hear me using both sets of terminology but i promise i'm trying
and i will tend more towards these in the slides all right so if we're looking at say
the biceps brachii you see that there are two proximal attachment sites two tendons
attaching more proximally and then you have one tendon that's attaching more distally
for any action that occurs there are typically more than one muscle involved likely there are
very many muscles involved and these muscles will have different roles or different functions to
allow the most efficient movement possible so let's talk a little bit about these roles right
the first one i think is usually the easiest to kind of um kind of understand and it's a
prime mover and a prime mover is exactly what it sounds like it is the main mover
or the main muscle responsible for producing the concentric movement and these will be the muscles
or the muscles that are using the most energy for that movement and this will be the more most
forceful of the contractions usually there is just one prime mover but occasionally there can be two
the antagonist will oppose the action of the prime mover and not saying i
pose i'm not going to let it happen it just will have more of an opposite action of the prime mover
so while the prime mover is concentrically contracting the antagonist will be eccentrically
contracting or lengthening in order to allow an efficient prime movement
so say the biceps brachii which we're looking right at right here is the prime mover and
one of its main actions will be flexing that elbow joint so decreasing the angle right here
but you cannot have the triceps brachii which is on the posterior side or the opposite side of
this muscle would be back behind the humerus you can't have that triceps brachii on the
other side also powerfully shortening and concentrically contracting at the same time
so it would need to eccentrically contract or lengthen in order to allow for that flexion
of the elbow joint so inflection of the elbow joint and we'll talk about this in much more
detail in upcoming videos inflection of the elbow joint the biceps brachii would be the prime mover
and the triceps brachii on the posterior side of the arm would be the antagonist
all right let's talk fixators fixators um oh and i we have a nice image kind of showing this here
but um let's focus again on the the fixator so the fixator is going to be a muscle that will
typically or most typically will steady a proximal part of a limb and this will help to allow more
clean and efficient movements on the distal portion of a limb and these are more isometric
contractions so there's contraction occurring there's tension occurring but no movement
occurring on that proximal end so it's kind of you know keeping that proximal end in place in
order for me to be able to forcefully contract some of the muscles on the more distal end
synergists often complement the actions of a prime mover not saying nice things ha ha but
what i'm saying what i mean more here is that it will complement by providing a weaker or less
energy consuming contraction that will increase the movement occurring with the prime mover and
there can be many synergists assisting a prime mover for any specific action so a lot of times
if you're making a list of all the muscles that could say flex the knee you wouldn't just have one
muscle you would knew you would typically have a list of you know four or five muscles particularly
in some of those bigger joints that could play a role so you would have one muscle that's the prime
mover that's using the most energy in terms of that contraction and allowing it to happen and you
have three to four other muscles that are playing a smaller synergistic role to the prime mover
so let's think through these concepts with a question
what type of a contraction would a muscle be doing if it were the prime mover for that action
so that that's kind of oddly worded basically what i'm asking what type of contraction occurs
with a prime mover is it shortening like what happens for a concentric contraction
or is it lengthening like a eccentric contraction or is it no movement like an isometric contraction
and hopefully you are thinking in this area here with concentric contraction or muscle
shortening eccentric contractions or lengthening would be more antagonistic
whereas isometric contractions would be more care characteristic of fixators all right thanks for
all your attention uh regarding this skeletal muscle tissue we are going to start getting
into some of the gross anatomy now we're going to start talking about specific bones we're going to
start talking about specific joints we're going to start talking about specific muscles and as
you might imagine there are a lot of all of those so we have a lot of fun things to pack through
and a lot of the terminology that we've covered in these first three topics will really help
with those conversations again thanks for all your attention and please have a great rest of your day