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NCLEX-RN
Course: NCLEX-RN > Unit 14
Lesson 1: Muscular system- Myosin and actin
- How tropomyosin and troponin regulate muscle contraction
- Role of the sarcoplasmic reticulum in muscle cells
- Anatomy of a skeletal muscle cell
- Three types of muscle
- Motor neurons
- Neuromuscular junction, motor end-plate
- Type 1 and type 2 muscle fibers
- Calcium puts myosin to work
- Muscle innervation
- Autonomic vs somatic nervous system
- Thermoregulation mechanisms
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Three types of muscle
Our bodies are equipped with three types of muscles: skeletal, cardiac, and smooth. Skeletal muscles, attached to bones and tendons, help us move voluntarily and quickly. Cardiac muscles, found only in the heart, work involuntarily and at a moderate speed to keep our heart beating. Smooth muscles, found in hollow organs and blood vessels, work slowly and involuntarily to control functions like digestion and blood flow. Each muscle type has a unique cellular structure. Created by Rishi Desai.
Want to join the conversation?
- When I sprain my ankle (for example), it swells up and hurts a lot (same for a fracture) - why ? What exactly happens to the bone, muscle, tendon or whatever is involved?
How is a ligament tear different from a sprain and why does it require surgery?
I don't know where to ask this, and I thought the muscle video was the closest :)(35 votes)- This one needs almost a whole video like stated by rishi but what happens is called inflammation on your ankle. If your doctor says it's a sprain it's a ligament that was damaged if it was a strain it was a tendon. These two words do get mixed up a lot and an easy way to remember is strain has a T which you can think stands for Tendon. Normally each case is different if surgery is needed depending on the ligament or tendons importance to function normally and the degree of the tear.(Such as a full tear or slight tear.)(39 votes)
- At, he says "One cell, one nuclei." Shouldn't it be one 'nucleus'? 8:40(6 votes)
- Yes, it should be nucleus, but you should think of how easy it is to make a mistake after lecturing for about 10 minutes straight.(44 votes)
- In athletics, you hear the terms, "fast twitch and slow twitch" fibers for skeletal muscle fibers. Do cardiac and smooth muscle fibers also share these characteristics?(17 votes)
- They don't. The fast and slow twitch grouping is for skeletal muscle. The structure and function of the cardiac and smooth muscle is much different.
The fast and slow twitch skeletal muscle, also known as type 2 and type 1 skeletal muscle, have key differences from the cardiac muscle cells, particularly in metabolism. Most importantly, skeletal muscle can function anaerobically, or without the consumption of oxygen, in addition to aerobically. This contributes to its ability to contract quickly! Without having to wait around to refill on its supply of oxygen for metabolism, the fast-twitch (type 2) muscle fibers can contract "fast". Slow twitch, or type 1 muscle fibers, have more mitochondria compared to type 2, which means they need more oxygen to get energy. The cardiac muscle cells function aerobically and have more than ten times the number of mitochondria than skeletal muscle. The contraction is much slower, and is also controlled by a pacemaker region. Finally, although the smooth muscle cells do not rely on oxygen to contract, they contract the slowest of all the muscle types due to a different mechanism of contraction.
Try checking out an older, possibly retired, khan academy video for some clarification...
http://www.youtube.com/watch?v=l5yMz2lFgx0(7 votes)
- Where do biceps, triceps, quadriceps and hamstrings fall under? Is is skeletal?(11 votes)
- They all are, yes. There's a few things you can use to tell, but the two best clues are where they are and what they do.
I'll use quadriceps femoris as an example. The four parts of quadriceps femoris originate from the ilium and the femur, and they insert onto the patellar tendon. They're attached to parts of the skeletal system, which is a good sign that they're skeletal muscles. The other simple test is whether they can be voluntarily moved. Quadriceps femoris is important for extending the knee joint. Because it's possible to voluntarily straighten the lower limbs, quadriceps is probably a skeletal muscle.(16 votes)
- Would the lungs be an Involuntary or Voluntary muscle? It does move all by it self, I don't need to be thinking about it but I can also stop it by holding my breath... Is it a complete different type of muscle that's half voluntary and half involuntary..(7 votes)
- The lungs don't actually "beat" on their own. The lungs are functionally like a balloon that fills the thoracic cavity. The diaphragm (which is skeletal muscle) and some other muscles change the volume of the thoracic cavity this changes the pressure and causes inhalation and exhalation. What changes is what it is controlled by for voluntary functions the cerebral cortex is taking over but normally breathing centers of the medulla oblongata and pons control involuntary breathing.(14 votes)
- Are all skeletal muscles voluntary?
Because what about reflexes? Skeletal muscles cause this movement, but reflexes are involuntary.(6 votes)- Yes, reflexes are involuntary. The important thing is that skeletal muscle movements and reflexes (medically called reflex arc) are controlled by different nervous responses. Skeletal muscle movements are controlled by the Central Nervous System(CNS) which is basically controlled by the brain. However, in earlier times, (I'm talking about at least thousands of years earlier, maybe millions) somehow Nature realized that if man's reflexes were controlled by the brain, it would take too long for the brain to respond before the person has to take an action... say, jumping out of the way of a predator. Hence, through evolution, somehow the spinal cord became in-charge of the reflex actions. This way, the brain is not involved and split-second decisions can be taken faster and ensure higher life expectancy.
If you guessed, all actions controlled by the spine(the reflex arc is not the only one) are involuntary responses and this system is called the Peripheral Nervous System(PNS).(4 votes)
- What is the difference between aponeurosis and tendons?(3 votes)
- Tendon--Thicker, looks more like a rope. Allows for movement and flexibility.
Aponeurosis--Thinner and wider. Allows for stabilization during movement, handling the pressure and tension from moving the muscles.
Does this help?(6 votes)
- Is there one muscle more important than the other?(3 votes)
- Not really. It is hard to rank them all because each of them have a good argument for being the best muscle. While you can say that the vestigial muscles (I.E: muscles of the ear) are less important than the others--as they no longer have a function--the other muscles of the body each have their own important functions.
All three types of muscles (that are not vestigial) do have some type of importance to the body. Without the skeletal muscles, you can't really move. You can't walk to get some food, or raise your hand, or move your eyes, and you can't even breathe (yes, the diaphragm is skeletal). Without the smooth muscles, several body systems will stop or be severely inefficient. Even if the all the missing smooth muscles were to be replaced with the other two types of muscles, you would still have problems (processes like digestion, which need muscles contracting at different times, would suffer if they contracted at the same time like a heart--and imagine telling yourself to digest your food!). Without cardiac muscle, the immediate, involuntary, and synchronized contractions will go as well. The smooth muscles do not function as one unit, and skeletal, voluntary muscles are out of the question.
Does this help?(5 votes)
- Why does the type of muscle matter?(3 votes)
- The type of muscle corresponds with their function. Striated muscles are better suited for bursts of expansion and contraction, while smooth muscles are better for handling smooth, sustained contractions. If the wrong type of muscle was in a certain part of the body, it would be very ineffective.(4 votes)
- Please explain the difference between aponeuroses and tendons?(4 votes)
- Pennate muscles, in which the muscle fibers are oriented at an angle to the line of action, typically have two aponeuroses. Muscle fibers connect one to the other, and each aponeurosis thins into a tendon which attaches to bone at the origin or insertion site.
A tendon is a projection of connective tissue beyond the ends of the muscle that attaches to bone. An aponeurosis is a broad fibrous sheet of connective tissue that connects muscles to adjacent muscles.(2 votes)
Video transcript
Let's talk about muscles. And I've drawn the
human body on the right, kind of a figure of it. And I want to talk about the
three major types of muscles. And I thought it would
be helpful to have a picture, because then we
can actually draw on there and show where the different
types of muscles might be. So when I mention
muscles, the word I want you to start thinking
about in your head is movement. So think about all
the different types of movements that might
happen in your body. Just be really
creative and start thinking of all the
different movements. You might have, for example--
a really easy one would be, maybe, let's say
your leg is moving. I'm going to just draw on
our picture as we talk. But let's say your leg is moving
because you're playing soccer. And so you've got this
giant muscle in here, and this muscle is
attached to a bone. Right? There's a little bone here. I guess not so little, right? This as the largest
bone in the body. It's called the femur. And so this muscle is
attached to the femur. And this muscle is going to
be attached by way of tendon. It's going to have
tendons on both sides. And so this tendon is
attaching it to the bone and allowing it to
act on the bones. So this is an example
of skeletal muscle. Right? So this skeletal
muscle is going to be attached to a tendon and bone. Now, that brings
up the question-- does every skeletal
muscle have to be attached to a tendon and bone? Well, the answer
is no, actually. There are some
muscles that really aren't attached
to tendons at all. In fact, right above
the muscle we just drew is a muscle called the
external oblique muscle. And don't worry so
much about the names. But the idea here is that
this muscle is actually not attached to a tendon. Well, in a sense, I guess, you
could think of it as a tendon, but it's like a flat tendon. Basically a giant kind of
sheet of fibrous tissue. And this fibrous tissue,
is it floating in midair? No. It's going to be connected
to fibrous tissue on the other side, because, of
course, your body is symmetric and so you've got fibrous
tissue on the other side. And you guessed it,
on the other side of that you've got
another external oblique. So you've got these muscles that
are kind of coming in to not really a tendon but
really a flat tendon, or something that looks
like a flat tendon, and we call that an aponeurosis. You might hear these words. I just want you to be
familiar with them. And now if someone asks
you, is every muscle in the body attached
to a tendon and bone? You can say no. Some are attached to a flat
tendon called an aponeurosis. The idea here is
that you can kind of start identifying
skeletal muscles. They're usually the muscles
that you can see on your body. Actually, I don't even
need to put quotes. That's the actual name for it. No need for quotes there. So you can identify skeletal
muscles pretty easily. But what about the other two? What about the cardiac
and smooth muscle? I mean, you might wonder,
does cardiac mean heart? And is that the only type
of cardiac muscle out there? And the answer is yes. This is your heart
muscle right here. And the only type of cardiac
muscle that we have in our body would be related to the heart. So in the heart, you can
find specialized cells that were so interesting
and different from skeletal and
smooth muscles, they got their own
name and category. These are the cardiac cells. And you can only find
them in the heart. I guess we're making a column of
where you can find these cells. So what about smooth muscle? Where can you find
smooth muscle? Well, for smooth muscle,
think about any hollow organ. Any organ that's got space on
the inside and blood vessels. Those are the two
major categories. Those aren't the only ones,
but those are the major ones. That'll get you about
95% of the way there. So blood vessels
and hollow organs are what you should think about. And hollow organs could be
anything from-- let's say, your stomach would
be a hollow organ. Let me just put
these examples here. Or your bowels would be a hollow
organ, anything like that. So I'm just going to
write stomach here just to jog your memory. Where there's basically some
empty cavity on the inside. Right? And then as for blood
vessels, just remember one of the largest blood
vessels, for example, is the aorta. And the aorta kind of comes
up and over like that. And it's kind of like a
hollow organ, as well. Right? I mean, there's a space on the
inside of that blood vessel. And blood is usually
flowing through that space, but at least it's hollow. So it's really not that
different conceptually from the hollow organ. And just like in
the hollow organ, the smooth muscle is in
the walls of these things. So think about where the
smooth muscle would be. It would be in the walls
of the hollow organ or in the walls of
the blood vessel. So that tells you where to find
these different muscle types. Right? And thinking about
movement, smooth muscle can help the stomach, for
example, move food forward. Cardiac muscle is going
to help your heart beat. That's a pretty
important movement. And skeletal muscle, I mean,
we use that every single day. Every time you give
your friend a high five or give your mom a hug,
those are skeletal muscles that are helping your
body move around. Right? So let's move on. Let's think about
some other differences between these categories. Let's talk about now
the movement control. So who controls the movement? Do you control it, or is
it automatically done? So smooth muscle is what I
would consider automatic, or I'm going to call it
involuntary because you'll probably see that
word more often. Involuntary just means that
your body is automatically taking care of it. And the same is true for your
cardiac muscle-- involuntary. Meaning, you don't
have to actually think about the next heartbeat. It just happens automatically. Right? And skeletal muscle is
the opposite-- there, it's voluntary. Meaning if I didn't want to get
up, then I would not get up. Or if I didn't
want to go running, then I wouldn't go running. All of those movements in my
body are under my control. I can decide when
to do those things. Right? Actually, maybe I'll draw little
arrows here-- what about speed? Which ones are fast,
and which ones are slow? So up here, the smooth
muscle is the slowest and the skeletal muscle
would be the fastest, which is pretty cool because
the voluntary stuff-- the stuff you control
yourself-- is the fastest. And the stuff that's happening
automatically is pretty slow. And actually it's nice, because
cardiac muscle is somewhere in between the two. Somewhere in the middle. So when your blood
vessels get tinier or they get big and
vasodilate, all that stuff is happening on a pretty slow
time scale as compared to, let's say, I jump and
try to catch a ball. That's all happening
really, really quickly. Thousands of little
muscle movements are happening really
lightning quick. And so those would
be the fastest. Now the final thing
I'm going to draw is what these things look like. So how do they look? If you actually take a
look at these cells-- let's actually look at each
of these one by one and figure out what
they would look like. So the smooth muscle actually
looks like a little eye, or like an almond-- sometimes
it's described that way. But I think of it as an eye. One single eye. And you can see that
the edges, or the ends, are kind of tapered like that. And so sometimes
you'll see that these are described as spindle shaped. I think that's kind of a
holdover from a time period long ago when people
thought about spindles more than they do now. And the other thing,
it's got one nuclei. Drew that right in the middle. One nuclei. And it's in the
middle of the cell. So that's basically what a
smooth muscle cell looks like. What about a cardiac cell? Well, this cell is branched. That's actually one of the
most interesting hallmark features of it. Now, not every single
cardiac cell is branched. Some are actually just kind
of humdrum-looking, normal, maybe like this. But the fact that you
can find branched ones is what really makes these
so easy to recognize. If you look at a
whole bunch-- I'm going to erase this guy now
that you know he exists, but I'm going to focus
on the branched one because these are the ones that
make them very easy to spot. And they also have nuclei. Sometimes one,
but sometimes two, which is interesting
because, you know, usually you think,
one cell, one nuclei. But the reason I had to point
that out for the smooth muscle cell, that there's only
one, is that sometimes these cardiac cells
have more than one. So the two features-- I'm
going to just write out here-- branched and
one or two nuclei. Not always two, but
they can have two. And they're also located kind
of in the middle of this cell. And I'll show you
what I mean by middle when I draw the skeletal muscle. I'll do that now. This is the skeletal muscle, and
it's got something like this. It's got these
little outpouchings I'm trying to draw for you. And you'll see in just a
second what I'm drawing. These are little spots on the
edge, or on the periphery, for nuclei. And notice that there's not
one nuclei, not two nuclei, but bunches of nuclei. So these cells are actually
working as a giant cell, in a sense. So these are actually, first
of all, they're straight. They're not branched. So straight. And they've got many nuclei. This is actually really,
really important, and you can see how it would be
easy to spot these guys, right? Because they've got many
nuclei, and the nuclei themselves are in the
periphery, kind of on the edges. That's why I wanted to point
out that the other two are in the middle. Now, kind of a final
point is that if you were to look at these under
a microscope-- and actually, this is something that was
noticed a long time ago-- they would look
something like this. And this is called striated. So they basically
have these striations. But notice that the smooth
muscle cells don't have this. It's really just the skeletal
muscle and the cardiac muscle that has these striations. Sometimes you'll hear
about striated muscle, and they could be talking
about either of the two. Right? They could be talking
about cardiac or skeletal, but you know that
they're not talking about the smooth muscle. So this is striated. And striated just
refers to those stripes. And that's what it looks
like under a microscope. And we'll talk about
exactly why they're striated what that would
imply about the cell in another video. But I just want
you to get a kind of a rough lay of the land. And now you can see
there's actually some interesting stuff here. You have some similarities
between the cardiac and the smooth muscle. They're both involuntary. You've got some similarities
between the skeletal and the cardiac. They're both striated. And so you can see how all
three are somehow similar, but also somehow different
from one another.