Chapter 9 Lecture A Types of Muscles

Chapter 9 Lecture A Types of Muscles


one of the most important
characteristics muscles is that they’re able to transfer cam
transfer chemical energy into mechanical energy that can be used carry out work so when we talk about a muscle there’s some
important vocabulary that we need to learn here at the beginning lot of these terms are going to begin with prefix myo or mys M Y S and both are roots of words that all refer to muscle so whenever we see the prefix myo mys MYS or sarco this is always referring to the muscle so let’s begin with some these basic
terms like the sarcolemma the sarcolemma is
the plasma membrane for the muscle and we’re gonna learn
that this is an electrical membrane we also have a sarcoplasm
which looks a lot like the word cytoplasm that you were introduced to in
Chapters three and this is going to be mostly fluid that is with in the muscle and within the muscle we have important
proteins these proteins are called myofilaments and two of the most important ones that you’ll need to know are call actin and myosin the actin is the thin filament and the myosin would be the thick filament one of the first part this chapter is
learning to differentiate between skeletal muscle
cardiac muscle and smooth muscle this slide is showing skeletal muscle the first thing that we notice about it
is that is striated and so it has these these lines that you’ll see it’s
highly organized and it is also voluntarily controlled which essentially means consciously controlled
so we choose to contract a skeletal muscle some of the other
important components of a skeletal muscle would
be that it is multinucleated so in this micrograph what we’re seeing here is one single skeletal muscle and as you can see all these dots are going
to be nuclei so there are many nuclei that are within a skeletal muscle this slide is showing cardiac muscle in the
first thing that we know it’s about it is that it has a branch pattern we don’t see this branch pattern in
skeletal muscle notice this is also going to be striated and it constitutes what makes up the heart pump the blood pump so it’s found in the heart but it is not
found in the blood vessels blood vessels are going to include smooth muscle so that’s an important
differentiation to be sure you are aware of cardiac muscle is going to be
involuntarily controlled so it is automatically controlled again it’s
striated just like skeletal muscle and it has what are called
intercalated disks the intercalated disks are going to
allow quick communication between many cells and this is especially important in the heart because we want an entire region of the heart like
the right atrium for example to act as one cell so it acts as what’s
called a syncytium a syncytium
means that many cells function as one cell it is subject to neural controls just like skeletal muscle but these
neural controls again are going to you automatically
control the heart so again it is involuntarily control we don’t
choose to tell our heart went to start contracting thankful we wouldn’t be alive very long if that were the case now the Intercalated disks are going to be made up of desmosomes as well as gap junctions which you learned about
back in chapter 3 next slide showing the
smooth muscle and smooth muscle is found in all the walls of visceral organs so organs like the stomach for example the urinary bladder the respiratory passages so the bronchioles would be one place that you would find smooth muscle also the uterus is where we also find smooth muscle and you’ll notice that it is nonstriated so there is essentially no lines that
are found in this histological section also smooth
muscle is going to appear spindle-shaped and so it’s going to be tapered at one
and you can see it one and here is kinda arm fat in the middle and it’s going to be uninucleate so the skeletal muscles really the only
type of muscle that is multinucleate so we can describe this type of muscle
as visceral nonstriated and also involuntary this is a table that you have towards the end of your chapter but I wanted to show it here because it nicely compares and contrasts skeletal muscle versus cardiac versus
smooth muscle so notice when we talk about skeletal muscle that is muscle attached to the bones or to the skin there’s gonna be
a tendon that anchors the muscle as you can see here is going to be
highly organized this area here within the highlighted area is
going to be one skeletal muscle cell it’s the it’s very highly
organized with the striations again it’s multinucleate cardiac
muscles in the walls of the heart it is usually uninucleate but it
could be binucleate it has striations its gonna have
this banding pattern but it is branch so we do see these
spaces between the cells because the cells have been pulled apart
but it does have these important intercalated disks that we see
right here in the highlighted area and then smooth muscle there can be two different types is
muscle there’s unitary muscle the walls of the hollow visceral organs but
there’s also a multi-unit muscle in some I muscles airways and
large arteries but they’re all going to have
one nucleus and they are involuntary and nonstriated there several important
characteristics of muscle there’s four that you should be
aware of the first one is excitability or irritability and both these basically
mean the same thing its an ability to receive respond to a
stimulus or any irritant that’s inside or outside
the environment so it could be a stimulus
like a chemical that could stimulate the
muscle to be able to respond so there could be a neurotransmitter
release from a nerve cell that could stimulate the muscle to contract there could be a change in local pH levels that could cause the muscle to become excitable and the response is for the muscle to
generate an electrical impulse and it generates these electrical
impulse along the plasma membrane which is going to be referred to as the sarcolemma so again remember the sarcolemma is the
plasma membrane for the muscle cell the second important
characteristic that you should be aware is contractility the abiltiy to shorten
forcibly this is what is going to set muscle
apart from any other tissue-type that we have the ability to
contract and it’s going to shorten because of the myofilaments which are the actin
and myosin we’re gonna spend a lot of time during this
chapter discussing this the third characteristic is
extensibility the ability to extend or stretch kinda like a rubber band and muscle cells are gonna shorten when they are contracting but they can but they can also extend which is elasticity so to be able
to recoil and resume their original resting length so the ability to extend and the ability to become elastic some of the other important muscle
functions are the idea of movement and movement would be things like
locomotion so being able to move in the environment to be able to move from one place to another to be able to manipulate our environments to be able to pick up something pick up a pencil and be able to write with it to be able to frown to smile to move
our eyes these would all be producing movement there’s also um other types muscle which are going to be
responsible for movement the locomotion and the manipulation
primarily skeletal but there’s also the movement of the heart muscle this
would of course be cardiac muscle in there is also movement of blood
through the blood vessels there is movement of urine movement of foodstuffs and these would
all be functions of smooth muscles specifically is the ability to maintain posture and
this would be referring to skeletal muscle stabilization of joints to strengthen the skeleton as well as generation of heat in these as well would be referring to skeletal muscle one of the first things
that our body does is we start to shiver when we get cold to generate heat so that
skeletal muscles are responsible for generating heat

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