Chapter 10 Lecture A Muscle Descriptions Lever Systems

Chapter 10 Lecture A Muscle Descriptions Lever Systems


the muscular system contains all contractile tissues well as skeletal
muscle muscle which we spent a lot of time
talking about in chapter 9 but also cardiac muscle as well smooth muscle during the first part of
this chapter you’ll be learning about how muscles move and the principal of
leverage so learning about how muscles provide
for a lever system by utilizing joints and also the various criteria for naming muscles so first of all muscles can only pull they never push and what one muscle group does the another is going to undo so what this
is essentially saying is that muscles work in antagonistic pairs and so a good way for you to learn the
names of muscles is to learn these antagonistic pairs one common
muscle that we’re all familiar with is our biceps brachii muscle which is going to be
very important for elbow flexion the opposing muscle of the biceps brachii muscle is the
triceps brachii muscle and this will be responsible
for elbow extension and so these are opposing muscles so the statement what one muscle group does
another undoes the first two examples like the biceps brachii and triceps brachii muscles and we’ll see other examples
of this is also applies to the quadriceps opposing the hamstrings and so all
muscles are going to have attachment sites what you learned about
in the last chapter recall that the attachments sites are called the insertions or the origins and the origin is going to be the point of
attachment to the less movable bone whereas the
insertions is going to the the point of attachment to the more
movable bone and a lot of these insertions or insertions and origins should
make sense to you as you know what the function of that specific muscle is so let’s go
through some terminology important terminology in naming muscles first of all muscles
are going to be in families or group and so when we think about the
family or the functional group um the main muscle in that group kind of
the leader of the group is called the prime mover or the agonists both these words are synonyms they are going to be the ones that are
responsible for the main movement of that functional group so an example of this if
we are thinking of the anterior chest muscles the primary movement of this group would be the pectoralis major muscle there’s also pectoralis
minor muscle but pectoralis major muscle would
be the prime mover of arm flexion the antagonist muscle
is going to be the one that opposes that muscle so when the prime mover moves in one
direction the antagonist
muscles is gonna stretch or remain relaxed so one example of this we had in the previous slide when we referred to the triceps the triceps would be the
antagonistic muscle to the biceps when the triceps is
contracting then the biceps would be the antagonistic muscle to the triceps so the prime mover which is the agonist and the antagonist are going to be on
opposite sides of the joint across which they actually act so in addition to these terms we also have the term synergist and a
synergist is going to be helping the prime mover in one one of these common ways as listed on your slide
its can add extra force to the same movement it’s gonna reduce undesirable or unnecessary movement and then the last um term is called the
fixator the fixator is gonna be in very important
because is going to give the prime mover a
stable base on which to act so all these are going to be very important terms
that are kinda referring to the family if she will of the skeletal muscle groups that we’re reffering to so when we are talking about the chest family the anterior chest or other upper arm family or the upper thigh
family this is what we are reffering to this slide showing action of the muscle um and it can be kind of inferred by the
position of the muscle relative to the joint that it crosses this is a
great focus figure is also the video relate this on the a & p flicks that you need to make sure
that you take a look at so as we look at our first slide the top on the slide right here if we look closely at it you can see the pectoralis major
anterior view and we can see that when these muscle
fibers are actually going to contract then the arm flexes and we can see the
direction in which it moves so again instead just memorizing all
these different actions if you can kind of act out the
movement of the muscle imagine where this muscles moving in your
body that will help help you to learn these the next one is
a very important muscle you be learning call the latissimus dorsi this is on the posterior view and is the
antagonistic muscle to the one letter A which is the pectoralis major so while
the pectoralis majors arm flexion one the major functions for
the latissimus dorsi is arm extension we use this for
swimming for example letter c is another important one called
the deltoid and you can see the deltoids very large
muscle here touches to the deltoid tuberosity what you learned
about in the previous chapter and it’s going to be important for a b duction abduction so to withdraw the arm from the body and then the antagonistic muscle is
located on the medial side the teres major would be an antagonistic
muscle to the deltoid and will help to adduct
to return the upper arm to the body so when we refer to these functional
groups the same muscle may actually be the
prime mover of the one movement it may be an antagonist for different movement or a synergist for the third movement so sometimes there can be a lot of overlapping and
we’re gonna be kinda oversimplifying the amount of movements
that are actually going to be related to each of these specific muscles and
to make things a little simpler that’s what
we’re going to stay with you’re not going to have to learn all the
different muscles all I like the major muscles you’ll be
responsible for so our next slide is showing the
criteria in which we use to name muscles it’s important you understand these so first of all
muscles are going to be named for the location so one example of this would be the temporalis muscle is located on the temporal bone
which you have already learned they’re also the intercostal muscles costal means rib these are gonna be
the muscles that are attaching the ribs another criteria is the shape of the
muscle and one example of this would be the deltoid
the deltoid is referring to a roughly triangular shape another example is the right and the left trapezius so when somebody says
they’re doing a trap exercise are using their traps
they’re referring to their trapezius muscles which is shaped
somewhat like a trapezoid another important criteria is the size of
the muscle you have probably heard of the gluteus maximus for
example this is an important muscle are butt
muscle which is the largest in the group then there if there’s a
maximus is also usually a medium a minimus a longus or a brevis depending on where its located a brevis
would be short muscle it could be a minor muscle which is in the case of the pectoralis
minor another important characteristic is the
direction of the fascicles we learned about fascicles in chapter
9 and if the fascicles run in a straight
line we use the term rectus there are several
rectus muscles to know actually a couple of major ones we are gonna learn called
the rectus abdominis also called 6-8pack and also the
rectus femoris so notce both of these are going to
use rectus abdominus refers to the region of the
body so muscle location and femoris refers to the femoral
region so again muscle location so one thing that will
help you learn the names of these muscles and what they do is to look at the words and go to figure
out what those words tell me specifically the word
transversus is referring to the direction of the fibers and we have also called the transverse
is dominance then we have the oblique fibers run at an imaginary axis of this which is oblique to the transversus dominance some of the other important
characteristics would be things like the number of origins and the biceps brachii the has two origins there is the biceps femoris the triceps brachii we also have the quad group and we
call this collectively the quadriceps femoris and this is collectively referring to the four attachment sites we also have the
location of attachments that are important and they’re gonna give you a lot of insight into that specific muscle so one good example of this would be the muscle called the sterno cleidomastoid which is kind of a monster to try to
learn but it gives you its name for the attachment
sites so it’s attached to the sternum the clavicle and also the mastoid process and then the last one is the muscle
attachments this is probably one of the most important ones because you have muscles are called the
flexor muscles the extensor muscles so one example is the extensor carpi radialis longus and so the first word is for the
function and then the of points attachment the carpals the radius and then also the length the muscles well so again when you’re learning these
muscles you want to focus specifically on the names and it will help you to learn what specifically they do another important thing is the
arrangement of these fascicles and the arrangement of the fascicles you should be able to recognize some of the
specific muscles that are named this way um they could be things like parallel pennate multipennate unipennate and the last thing we are gonna talk about in this first
lecture is a lever systems so the first pattern organization of the fascicles would be circular fascicles when they circle an area and these are going to be concentric
rings they would be things like the orbicularis oris another example of a muscle woud be the orbicularis oculi which is surrounding the eye closes are eye another example would be sphincters we have hundreds of sphincters in our body and these are circular muscles they’re going to be constricting a
certain area another arrangement for fascicles would be the convergent
arrangement and in this case there’s a broad origin and the fascicles are going to
converge on a single insertion point so the pectoralis major
muscle would be an example this the one that is
responsible for arm flexion we could say flexion of the humerus another arrangement of
fascilces would be referring to the parallel arrangement and in this case the fascicles run
parallel too long the axis of the muscle some of these muscles are
gonna kinda looks strap like and one of the best
examples of this in the body would be the sartorius muscle this is
a muscle that we used to cross our knees and then the next one will be the fusiform
muscle and the fusiform muscle um in a fusiform muscle there’s gonna be a
spindle shape muscle that has parallel fibers but it’s gonna come to a point it’s gonna fuse at one specific end an example this will be the biceps
brachii muscle the one that is responsible for elbow flexion so when you’re describing the functions
of these muscles you wanna be particularly careful to
describe the joint at which the action is occurring some sort of pasta but in this case there
is going to be a central tendon and then they’re going to be fascilces that are going to run at an oblique angle to the central
tendon so if we have one group of fascilces running oblique to the
tendon this would be called unipennate what’s kinda interesting is that
if you look closely at the organization for leaves you see a similar structure makes you
think so now first of all unipennate a good example of unipennate would be the extensor digitorum longus bipennate would be something like
the rectus femoris an important muscle
that you can have to know this muscle is going to be the prime mover of the quads prime mover the quads group then we have multipennate kinda looks
like there’s feathers side by side multiple arrangements one classical
example of this would be the deltoid and the deltoid is going to be
again for arm abduction so this is the figure they have in your
book and you can see with the arrangements for
convergent you can see that the origin is going to
have a broad area here this is origin then the assertion is gonna come to a
specific point and then for the fusiformit is
spindle-shaped so kinda fat in the middle and then it fuses at the two ends
so would be an example the biceps brachii there we do have the sartorius kinda
looks like a strap like muscle then we have the circular orbicularis oris
remember the one that is also surround the eye the orbicularis oculi is also going to fit into category letter a the circular also the
sphincters are examples of this you learn a lot more about different
sphincters in anatomy and physiology two then we also have the various pennate
designs we have the unipennate extensor
digitorum longus the bipennate rectus femoris as well as the deltoid the multipennate so the arrangement of fascilces they aren’t really just for design and they’re also very important the amount of range of motion that is going to be permitted by that particular muscle and so the amount of movement is going
to occur when the muscle does actually shorten determines the
muscles power so long fibers are more parallel too
long long axis are gonna shorten much more simply something like the sartorius and
then the power also depends on the number of muscle fibers so the amount of fascilces is very very important so the last part in this first lecture
is on levers now and there are three different lever
systems that you need to know lever system is made up of three
important components the first one is going to be referring
to the lever the lever itself and the lever is
the rigid bar which is going to be the bone that moves
on a fixed point called fulcrom and the fulcrom is the joint the effort is going to be supplied by
the muscle contraction and then the resistance is going to be
the load and the resistance could be just the bone and the tissue but it could also be the
added weight so if we are using the biceps brachii as an example if we are going to flex at our elbow which remember is the function of this muscle if we’re just
gonna flex or do an arm curl we’re doing arm curl
without anything anything in our hand the resistance in
the load would be the radius and the ulna that were left in plus
the tissues but if we have a drink in our hand and
were curling that then that would be the added weight
which were also account for the load as well so when we think about lever systems we
have a couple different types these levers are going to allow give an
effort to move a heavier load and possibly to move that
load farther or faster so what can either create mechanical
advantage or create a mechanical disadvantage mechanical advantage is commonly
referred to as a power level lever in this occurs when the load is
very close to the fulcrum or the effort is far
from the fulcrum so in this example a person can lift a
car with the power lever so we see a mechanical advantage that is
shown in this example right here and you’ll notice that the load is very close to the
fulcrum in this case or the effort is very far from the
fulcrum and this is just kinda f.y.i these
calculations here for your information you not gonna have
to actually calculate this this is just getting an application of
the lever system choose something that we’re commonly
used to the other type of lever system is gonna be the one that has mechanical
disadvantage and the one with the mechanical
disadvantage the load is going to be far from the fulcrum or the effort is close to the fulcrum and the example of this would be when
we’re using a shovel and this this in this case is going to put a lot of
extra strain on the back specifically so these are
the two main types lever systems so let’s look at each of
these the basic principles of the levers are
the effort and its relationship to load and the
fulcrum and need to know these three different
lever systems and the samples of where we find these lever
systems in the body first lever system is going to occur
when the arrangement of the elements is load fulcrum and then effort so it’s almost like
there’s a seesaw the fulcrum is gonna be the joint in the
middle and then there is the effort from the
muscle and then also the load on the opposite end a common example of this would be also
scissors so in our we see this example shown here
on the slide so again you can see the fulcrum is in the
very middle and each case the effort for the scissors gonna is
going to be applied by the force that we use to actually use
the scissors and the best example this in the by the
one example the need to be aware of is the one that is applied by the sternocleidomastoid muscle so the sternocleido mastoid muscle is going to be applying the effort so we’re going to use this um lever system in order to lift our
head up to extend our head or possibly
hyper-extended our headed for looking too far and notice that it the joint in
this case is going to be at the atlanto occipital joint so recall that this is a
joint allows you to nodd your head yes and again it is a first class
lever system as you raise your head off of your chest so the load in this case is going to be the weight of the head then if you put a really heavy hat on then
that hat would also be added to the load too that you would have to lift with your
sternocleidomastoid second class lever system is um arranged in such a way that the
fulcrum is gonna be on the end the load is in the middle and then the
effort is in the middle so one thing that can
really help you is to remember the order of these elements and one example of this would be a
wheelbarrow and also standing on our toes you need
to know the muscle that’s responsible for standing on our
toes we can see in this case that with the
wheelbarrow the fulcrum is the joint and it’s on the very end
the load is the wheelbarrow plus the mass that we put in the wheelbarrow and effort is the muscle contraction
that we used to actually lift the wheelbarrow the next slide is showing the muscle responsible for
this this muscle would be are gastrocnemius
muscle and the gastrocnemius muscle is
responsible for plantar flexion plantar flexion means that we stand on
our tiptoes so the next one is the third class lever in the third class lever um in this case the effort is applied between the
fulcrum and the load so the order would be load effort and then the fulcrum would be on the end and in this case is considered to be a power lever the best example of this
would be in the biceps brachii muscle here we see an
example other with and some tweezers or forceps so the third class lever is going to be what is applied by the biceps brachii
muscle so it’s important that you know that the biceps brachii muscle represents a third-class lever system

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