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BIOL 2301 Human Anatomy & Physiology I - BIOL2301 lecture14_0305
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00:08 Microphone is working. All right. A couple of reminders we have a
00:12 on Thursday, so don't show up . Right? Excited about the
00:17 Not at all. OK. Um today's lecture, is it on the
00:23 ? No, it is not. last stuff that's gonna be on the
00:25 was the stuff that we talked about Thursday. So through action potentials and
00:30 synapse, et cetera, et So everything through Thursday is on the
00:34 and then after Thursday, what do have spring break? Use it
00:41 meaning use it to rest, catch up that sort of thing.
00:47 right. Uh Today, what we're do is we're going to talk about
00:51 . Um And the thing is, in anatomy, what they typically do
00:56 what, what uh most classes will is because they're usually associated with the
01:01 is they'll spend a lot of time about the specific muscles. All
01:05 So if you're taking the lab or be taking the lab, you'll be
01:08 going through and learning the names of muscles and what they do, it's
01:12 lot more difficult to do that in lecture environment because all we would be
01:16 , looking at pictures going and this what this muscle is and this is
01:19 it does and that's not particularly helpful learning it or anything. It's usually
01:23 a waste of time and very So what we typically do here is
01:27 tend to focus more on what a structure is and how it goes about
01:32 physiology. In other words, how goes about creating a contraction. So
01:37 lecture will fill physiology, heavy. that's ok. That's how we're going
01:41 go about it. All right. uh in terms of functionality, that's
01:45 we're gonna start is like, all . Well, what do muscles
01:48 And, and the truth is there three different types of muscles. We
01:51 skeletal muscle, smooth muscle, and muscle. We're gonna focus primarily on
01:56 muscle. All right. And the we focus on that is because it's
02:00 easiest to understand, it's the most , it's easy to look at cardiac
02:04 is very, very similar to skeletal , but you'll deal with that when
02:07 get to the heart. All And that's going to be an A
02:09 , too smooth muscle. We'll talk little bit about on Tuesday when we
02:13 back from spring break after you've forgotten we learned here. In fact,
02:17 probably suggest that this is probably the lecture, not because of the
02:21 but because literally your brain is not today. Your brain is already thinking
02:25 spring break or you're thinking about the , right? So, you're not
02:29 focused in this area and then you're get a whole week and a half
02:34 forget everything we've taught and truthfully, mean, I forgot everything I taught
02:38 Thursday. I was coming in and like, what am I supposed to
02:40 ? Oh, yeah. It's a unit. So, it's, it's
02:44 uncommon. So, just kind of in mind. Yeah, I've gotta
02:48 sure that I kind of remind myself this stuff is about when we get
02:52 . All right. So our focus primarily the skeletal muscle and skeletal muscle
02:57 pretty straightforward because we can think about terms of its function. It primarily
03:03 a role in movement or locomotion. right. So when you see me
03:07 here walking around and doing stuff that's skeletal muscles job. All right.
03:13 it's a little bit more nuanced than . It's a little bit broader.
03:16 , one of the thing that it , it plays a role in protection
03:18 support. We don't really think about in that way. But if you
03:21 about your internal organs, they're being held in place by the skeletal
03:26 of the thoracic and abdominal region. they do play a protective role as
03:32 . They help to maintain your posture stabilize your joints. And this is
03:36 something you don't even think about, sit upright and walk upright, not
03:41 of conscious thought, but because your is constantly contracting or causing these muscles
03:47 contract in an unconscious way. That mean that they're not voluntary.
03:52 for example, if I said sit , usually I get at least two
03:55 three people to do that. Maybe a little bit later in the
03:59 All right. That's when you just of, oh, yeah, I
04:02 control those muscles, skeletal muscles are . Uh They generate heat. You
04:08 noticed that just by living in the or down here in the south,
04:11 like every time I move around I sweating, it's because, uh,
04:15 not particularly energy efficient as an And so when a muscle contracts,
04:20 burns energy to create that contraction and gonna see that it's a little bit
04:24 nuanced than that. Uh But uh gonna happen is that, that heat
04:29 generated uh, as a result of inefficiency, energy usage. And so
04:34 produce the heat now, we can this heat, uh uh in certain
04:40 to warm the body. And so is not so common down here in
04:44 , but if you get really, cold, what do you do?
04:47 shiver? Right. And that's basically muscles contracting really, really fast to
04:51 a lot of heat very quickly to your body warm. Um, the
04:55 thing and this again is part of producing movement thing. But it's a
05:00 bit more specific is that it is or skeletal muscles are used as a
05:05 of communication. Now, the easy to think about is when you see
05:08 talk up here, I'm, I'm gesticulated. I use my hands and
05:12 like that. So that's easy to that movement. But when someone is
05:16 to you and you start seeing him this, you, you can kind
05:20 understand, oh, they don't like I'm saying. They're communicating back to
05:25 , not in a vocal or uh vocalization or in a verbal way,
05:31 they are signaling, using their face , their displeasure with the thing that
05:36 discussing. And if you see someone and other stuff again, using your
05:40 muscles, these are all skeletal muscles conscious control, but they're not actually
05:47 movement. It's a form of communication truthfully one of the things that humans
05:52 really good at is nonverbal communication through expression, right? So, uh
05:59 typing and writing, that's also, know, a type of communication,
06:04 that's more a movement. All So with that in mind, what
06:07 gonna do is we're gonna dive in we're gonna start looking at muscles.
06:11 so this is, this is my for why we don't do the,
06:14 memorize all the muscles. And what do is there are over 600
06:18 skeletal muscles in the body, in a typical A MP lab,
06:22 will learn about, uh anywhere between 100 of them. So, and
06:26 are like the big ones. so, uh we're not gonna do
06:31 here, but just be aware, lots of them, each of them
06:33 their own organ, right? So you see a muscle, you need
06:37 think that is an organ, it independent of the other muscles in my
06:42 . And so that's why we consider a separate organ system. So each
06:46 these name muscles, independent organ I'm just going to warn you.
06:52 , I reverse these on my So just make sure when you're looking
06:56 them that you're looking at them in right order. I did this on
06:59 because I usually typically talk about the side. And so what we want
07:02 do is we want to think in of a muscle itself, one of
07:05 named organs consists of a muscle it's going to be nerves that are
07:10 to be involved, there's going to blood vessels that are going to be
07:13 . So we're already starting to see components of these different types of
07:17 But one of the other things is going to see is connective tissue and
07:20 connective tissue is actually worth talking And the reason for this is that
07:25 muscle, the the the the bulk the muscle, the belly of the
07:29 . The thing that does the work organ is consisting or has different layers
07:34 connective tissue that are associated with that that then extend beyond the muscle
07:40 And it's what the muscle is actually on. And so what this picture
07:44 trying to show you is, look, if I look at a
07:47 muscle, so that the fat part the muscle is called the muscle
07:51 I can break it down. If start diving in deeper, I'm going
07:54 see their bundle of fibers and these are the individual cells. And so
07:58 we're looking at here, that is muscle cell and you can see it
08:03 down even further into the cyto skeletal and the individual fibers that make up
08:07 elements. But this right here is actual muscle cell. We refer to
08:11 muscle fiber. It is as long the muscle itself. So if you
08:15 think of any sort of muscle in body, I'm going to point to
08:17 muscle. This is my bicep, ? That bicep connects from here to
08:24 . OK. So the cells in muscle are the length of that entire
08:30 organ. So they're very long All right. And each individual cell
08:35 wrapped in its own connective tissue. the reason for that is each individual
08:40 needs to be stimulated electrically without stimulating cells around it. All right.
08:45 we have a name for that connective , we call that the Endomysium.
08:49 right. So that's the endomysium. can see here, what we have
08:53 the muscle fiber, it has its plasma membrane and then wrapped around that
08:58 membrane is a layer of connective That's that Endomysium. And if you
09:03 a bunch of these individual cells in own connective tissue, and you wrap
09:07 bundles of cells with connective tissue, where you get the para misi.
09:12 right, we call this bundle a . And then if you take a
09:17 bunch of fascicles, so here's your . If you take a whole bunch
09:21 fascicles and wrap them up in connective , that would be the epimysium.
09:26 right. So you can see that have an individual cell wrapped in
09:31 take a bundle of those, wrap in a connective tissue, take bundles
09:35 the bundles and that's your whole muscle . All right. And it's this
09:40 tissue, all three layers, the , the paramecium, the Endomysium,
09:44 extend beyond the length of the cells the length of the fascicle beyond the
09:49 of the muscle and they extend and , that's what attaches a muscle to
09:53 bone. All right. And what call that structure is a tendon.
09:59 right. So, tendons are the tissue that allow that are pulled on
10:05 the muscles to move the bones. , tendons are typically uh cord like
10:12 usually roundish but you'll find things that flat and when you see them
10:15 that's called an A, um, , now I'm blanking on its
10:20 Is it up here? No, not. Um, it's an apo
10:24 . I'm not gonna get it. . I'm, I've, I've already
10:27 on it. Uh, aosis. we go. Um, anyway,
10:32 , uh, they're gonna be attached that periosteum on the bone. All
10:37 . So, when I'm pulling I'm not pulling the bone directly,
10:41 pulling on a tendon. And because tissue has a little bit of stretch
10:44 it, you're gonna see a little of stretch before the bone even starts
10:48 . And this is gonna be a that we're going to deal with.
10:50 probably on Tuesday when we return. , this picture gets a little confusing
10:57 what you have to do is you to imagine I am now inside that
11:01 cell. All right, remember it's a muscle fiber. And the reason
11:05 say it over and over again is we're going to deal with fibrils as
11:09 . And that gets kind of confusing you have the same word repeated over
11:13 over. So you may hear the myofiber, myo as a prefix,
11:17 to muscle, sarco as a prefix to muscle. All right. So
11:22 you see those two things think of belongs to a muscle. So the
11:27 or the muscle fiber is represented here this entire thing. All right.
11:34 here that would be the plasma we call that the sarcolemma and inside
11:39 plasma membrane that we're going to have cytoplasm, right, which we call
11:44 sarcoplasm. And then you have the skeletal elements, which is what these
11:49 giant bulgy things represent. Ok. there, you'll also see a couple
11:55 other interesting structures. We have a reticulum, which is the endoplasmic reticulum
12:02 the muscle fiber. It's a modified reticulum. It's a smooth endoplasmic
12:07 Its job is to sequester away So it's a place where we're going
12:12 store up calcium. All right, have mitochondria, lots and lots of
12:18 . We have multiple nuclei and the you have multiple nuclei is that this
12:22 not one cell. This is a of many cells joining together to make
12:28 really, really long cell. This very early on in development. So
12:32 muscle cells start up as little itsy , teeny tiny cells and they start
12:35 up together and they create this larger cell. There's also this material called
12:42 in it. Myoglobin is related to molecule called hemoglobin. Hemoglobin is what's
12:47 red blood cells and what carries oxygen your body. All right. So
12:52 that you know what hemoglobin is, do you think myoglobin does if a
12:56 carries oxygen in your body, what you think myoglobin does? It keeps
13:01 in your, in your muscle why would I need oxygen?
13:05 if you've learned anything about biology, know that your cells need oxygen and
13:10 to do their job. Right? that, that's like the one thing
13:13 you carry from class to class to oxygen, glucose equals good equals
13:18 Well, do you want your muscles wait for oxygen to show up for
13:22 to start contracting now? Right. you're walking across campus and Shasta pops
13:28 of the bushes and says, lunch because that's what Cougars do,
13:33 ? You don't want to sit there go. Ok. I got to
13:35 breathing fast to get the oxygen into body. So I can get those
13:38 going. You want the cells to that storage of oxygen in place and
13:41 the job of myoglobin. It puts oxygen there so that you have an
13:46 pool of oxygen so the muscle can contracting. All right. Now,
13:50 , we have this really weird looking . All right. So the blue
13:55 here, that's the sarcoplasmic reticulum. you can see here in the little
13:59 there's this little yellow thing that goes the way through and they're trying to
14:03 it over here as well that it's are tubes and these tubes basically wrap
14:07 the side of skeletal elements just like sarcoplasmic reticulum dub. But the tube
14:11 open to the surface and then it through like a tunnel and opens up
14:15 the other side of the cell. these tubes are called the transverse
14:21 The transverse tubules and the sarcoplasmic reticulum ju uh very, very close
14:28 And there's another part of the sarcoplasmic that's been identified and kind of is
14:32 its own name, but it's part the sarcoplasmic reticulum. This is called
14:36 terminal cister, terminal, meaning on end cistern, meaning bulge. All
14:41 . So the together the sarcoplasmic the t tubule or transverse tubule and
14:49 terminal cistern are collectively referred to as triad. They work together to accomplish
14:56 one of the major goals of the cell. Now, cardiac cells they
15:02 diad. So the reason we point triad is because there's a slight difference
15:06 a cardiac cell. All right. , what does this do?
15:12 if the sarcoplasmic curriculum is responsible for of calcium, it's the biggest part
15:17 the sarcoplasmic reticulum is the terminal cisterna next to the transverse tubule. All
15:24 . And so the transverse tubule brings surface of the cell internal to the
15:30 . Does that make sense? In words, if I have a tube
15:33 through something that means I've got a of surface area, that surface area
15:37 not just stuck on the outside, surface area comes on the inside like
15:40 doughnut, right? Think about a , the hole in the doughnut.
15:44 means the surface is not just out , the surface is also there.
15:48 that's what we've accomplished by these terminal by these transverse tubules is we've made
15:54 that bring the surface into the inside the cell. That kind of make
15:59 . Or no, I've seen one nod. All right. Is
16:04 that doesn't make sense. All Did the doughnut not work? Have
16:09 , do you, have you ever a doughnut? Ok. I'm just
16:11 sure because if you don't, can't the doughnut. All right, I
16:15 you to think for a moment about digestive system. All right, you
16:19 know your digestive system. What is opening of your digestive system? Your
16:24 ? All right, the mouth brings outside internally. All right, it's
16:32 tube that travels through your body. that what I'm doing is anything that
16:39 into the digestive system is not actually my body. It's in the tube
16:44 travels through my body. Does that sense? Right. So my body
16:49 all the stuff on the outside of tube and on the inside of my
16:55 portion of my skin, right? that tube is always external. See
17:03 right here. It stays outside. body poop never is inside your
17:07 Where is it? It's always The body. Food is always outside
17:11 body does that makes sense. Let's at the lungs. All right,
17:16 is out here when I breathe does the air go in my
17:21 No, it goes into this cavity is sustained through my mouth and my
17:28 cavity down through my trachea and into larger structure called the lungs, it
17:34 outside the body, air does not into my body. I move molecules
17:39 the air into my body. All , let me think of another one
17:44 . Kidneys, renal system dit or the renal system. All
17:49 there is a point where material is from inside the body to outside the
17:55 . So that's what the job of kidney is. And then once you
17:58 urine, urine is outside the it finds its way into the uh
18:03 . It's in the bladder, it's the urethra. Those things are outside
18:07 body, anything open to the external is outside. Does that make
18:13 Ok. So with that in I want you now think of this
18:16 , you have a cell and a that travels across the length of that
18:22 of like your digestive sy system opens the mouth. And then where else
18:26 it open? On the back side the anus? Right? That's a
18:33 that goes through your body. These tubules do the exact same thing.
18:38 , we haven't said what they do what they, but in the sense
18:43 context, the surface is starts on outside. And then when there's a
18:49 , the surface continues down through that just like your digestive system continues your
18:56 through your body. Does that make ? Now? Makes sense. Makes
19:01 back there. OK. All We're gonna get to why this is
19:07 in just a minute. This is putting all the players onto the field
19:11 then we're gonna talk about what all players do. All right. So
19:16 nuclei, we've got the triad. triad is made up of sarcoplasm
19:20 the tri uh the t tubules as as this terminal cysto of the sarcoplasmic
19:25 . All right, we can see big giant set of skeletal elements in
19:29 , right? These are called the , the myofibril and this is what
19:35 doing, going back to our little . So, here's our mu muscle
19:39 , the myofibril are the cytoskeleton. right. They're made up of the
19:45 that we've already talked about. There's two different types of filaments.
19:52 . We have a thick filament and have a thin filament. The thick
19:57 is made up of a molecule called . All right. Mycin looks like
20:03 bunch of golf clubs that have been together. All right. So what
20:08 have is they have these long tails then they have these heads and there's
20:13 two of us looks like two golf have been wrapped like someone's had a
20:16 bad day at the golf course, ? And they wrapped them up and
20:19 two heads are sitting like this and move like, so I guess like
20:26 twenties, boxers, 18 sixties, ? So that's the thick filament and
20:33 have thousands upon thousands of them wrapped so that they're all facing the same
20:38 in multiple units. Like, so thin filament on the other hand,
20:43 made up of three different components. if I named them, there's a
20:48 that they're important. OK, we acted. Acton is a series of
20:55 . They create these long strands. not, you don't even know facin
20:59 G Act and I just have that there because it's acting Act and
21:02 All right. And it creates these ropes. Myosin has on the
21:09 a uh binding site for Acton. wants to interact with Acton. Acton
21:16 on its uh uh structure which is well shown here has a my in
21:21 site. So these two things want get together and when they get
21:24 they bind up in a, in reversible way and they, they work
21:29 . The thing is you don't want always binding together. So associated with
21:34 is another molecule called trom Mycin Mycin is related to Mycin. It
21:43 loosely affiliated with the Mycin binding site Acton. And what it does is
21:48 covers that Mycin binding site. So little green strand that you see wrapped
21:55 is blocking or preventing Mycin from binding it's there doing that job. So
22:03 and Acton want to get together but mycins in the way and then associated
22:08 Tropomyosin and associated with acting together is molecule called troponin. And that's what
22:16 little peak dots are representing. troponin is an interesting molecule. It
22:21 like a hinge. So it's bound to, to act in like so
22:27 it's bound up to Tropomyosin. So three molecules together form something called the
22:34 filament. Now it acts as a and so its job is to move
22:39 Mycin out of the way so that can interact with it. All
22:44 And so what we're going to be in terms of the question of,
22:49 , how does a muscle contract? we're gonna be answering is how do
22:52 molecules interact with each other? What the things that allow them to interact
22:56 how do we move these portions of thin filaments out of the way so
23:01 , that interaction can take place? right, that's really what the big
23:06 microstructure or the, the big question going to be answered. All
23:12 Yes, sir. OK. So question is, what is the difference
23:19 myo filaments and myofibril? Great All right. So the myofibril is
23:27 bunch of these things together. you can't really see in this picture
23:31 it's not really easy, but you think about it like this for every
23:34 filament, there are six thin So you can see here is
23:40 Pick your, your little hexagon, another thick filament, finish out the
23:44 over there. Put another one, one, another one. When you
23:47 at somebody who has big muscles and is where I kind of look around
23:51 room and I try to find our real weightlifter. You know,
23:54 ones who are dedicated, the ones have like mass, right? When
23:59 see someone with that big mass of , what they've done is they haven't
24:03 more muscle cells. What they've done they've added more of these myofibril strength
24:12 a muscle is in the number of . All right, think about this
24:17 . Each of these represent a That's an easy way to think about
24:20 , right? If I put more to pull something and have more people
24:24 pull on those ropes, are you be able to move an object that's
24:27 and bigger and bigger? Yeah. that's kind of the same thing is
24:31 , oh, I need to move bone if I want to move the
24:34 faster, what do I do? put up more frills. All
24:38 So then you say, well, a myofilament? The myofilament is what
24:43 up the myo frills. So do see what we've done here is
24:46 we worked down to the most tiniest . So this is a myofilament.
24:54 is a myofilament. These things collectively in their arrangement is the myofibril.
25:01 right. And that's what's creating this structure. This is the representation of
25:10 of the thick and the thin filaments . That's the myofibril. All
25:14 And you can see in an individual , do I only have one
25:19 No, I've got hundreds of So it's like cell, hundreds of
25:25 cyto skeletal elements, hundreds of myofibril them. And in each of those
25:30 , I've got hundreds of myo filaments thousands. I mean, so
25:35 I want you to understand there's a . All right. So if you
25:41 to look at a microscope under a , like the first people who are
25:45 to figure out how the human body , they cut off muscle, they
25:48 it, they looked in, they're , wow, they're stripes, you
25:51 the stripes and they started counting the and they said, oh,
25:55 there's a light stripe. I'm gonna with, I'm gonna start with a
25:59 stripe here. But what I'm gonna is, oh, there's a light
26:01 . Then it becomes dark, then becomes light again, then it becomes
26:04 dark and then it becomes lighter then it becomes dark again and then
26:07 light again and then I'm repeating the . Now, if you're looking at
26:11 I can't see that that's because this a really crappy picture, but there
26:15 a lighter area in here relative to and you can kind of see it
26:20 in this. So if this is line that I'm starting with, you
26:22 see it's light, then it's really , then it's mostly dark, not
26:27 dark and then it gets really dark , then it gets really light and
26:30 that line appears and like a good . When you see a pattern,
26:34 start naming the things in that And so we said is,
26:39 um we're gonna call this an an , we're gonna name it an I
26:44 and I don't remember what the abbreviations . So, what we're gonna do
26:47 we're gonna start with an I band half an I band and then we're
26:51 begin and we're gonna start dealing with A band and the A band extends
26:57 the way till it ends. So all that dark, but in the
27:00 of that, a band, we this lighter region and we're gonna refer
27:04 this lighter region as an H band the middle of that H band.
27:07 have a dark region again, we're call that the M zone or the
27:10 line. And then we're gonna repeat see the other half of the I
27:15 . And so what we've done is defined a unit that is a repeatable
27:19 inside the muscle. And this repeatable we refer to as the sarcomere.
27:26 , back when they were naming they didn't know what it did,
27:28 the sarcomere is the functional unit of muscle cell. So as you grow
27:34 get bigger, your Sarker don't stretch and get longer. What you do
27:38 you add new sarcomas to the end your muscle cells. All right.
27:44 the length of your muscle is a of thousands upon thousands of itsy bitsy
27:49 sub units of these repeating myo myo inside that muscle cell. And that's
27:56 the sarco area is. All And that's what this is trying to
28:00 to you. And here you can a little bit more clearly the relationship
28:05 the thick and the thin filaments. what this is trying to show
28:08 It's a cross section through a All right. And what we have
28:13 is in essence, showing you the of these different fibers. All
28:19 So the Z line, which is we start everything. That's that boundary
28:25 the sarcomere. So you go to line and you go all the way
28:28 to another Z line. And so calling that the Sarker, when you're
28:32 at that, what you're seeing is line that looks like this. But
28:35 this is something in cross section. if you turned it this way,
28:39 see that it's a lattice of proteins this lattice of proteins is bound to
28:45 in filaments. And so what you are acting filaments extending from that Z
28:52 , that's what all that represents. if I was the Z line.
28:55 my body was the Z line, you'd see is you'd see a whole
28:58 of Acton extending away from the Z in both directions, right? And
29:04 you have only those thin filaments, is what we refer to as the
29:09 band. So in this region in this region, here,
29:14 there and there and just keep just find your Z line.
29:18 There's a Z line, there's a line, there's a Z line in
29:21 sarcomere, you can see that the bands are the first thing you
29:25 And that's only the thin filaments, thin filaments remember want to interact with
29:34 thick filaments. And so there's this of overlap, the thick filaments are
29:40 from the M line. All So you can see here there is
29:43 thick filament extending from the M line that M line just like the Z
29:49 , you're looking at it like But if I turn it this
29:51 it's a lattice of proteins, those have extending from them in both
29:55 thick filaments, if I'm the M , I'm the thick filaments going in
29:59 directions. So what we're seeing here the thin filament overlaps with the thick
30:05 . So we're seeing where these two cross each other. That is the
30:09 band. So the moment where they , that's what's going on. Now
30:14 show you this, I'm going to his arm, put your arm
30:17 All right. So if he's a filament, can you guys see it
30:20 there? No, I'll do it on that side too. This would
30:23 the thick filament. So, if is thin filament, this is all
30:27 band. And so the moment the where they overlap, that's the thick
30:31 the thin together, that is a . So thick filaments and thin filaments
30:36 , overlapping are a bands. All , I'm gonna steal her arm and
30:40 just going to do the same just stick your arm out. So
30:42 can. So if she's a thin and I'm a thick filament where we're
30:47 from here to there, that's all band where there's overlap here, that
30:52 be a band. OK. Then have this region where there's no overlap
31:00 thick and thin filaments. It's just filaments, right? You can see
31:04 right there. That region where it's thick filaments. So I'm the in
31:08 . This right here is all thick . But remember I have a thin
31:11 coming this way, but where there no overlap moving towards the M
31:15 that would be H band. So goes, I band to a band
31:20 H band M line and then I go the opposite direction. Ha
31:25 all right, want me to help remember this. What is the three
31:32 designation of intergalactic or intercontinental? Does know Iah, for us. That's
31:44 . Right. I mean, that's the name of our airport.
31:48 . So you can remember it from Z line and go iah. All
31:53 . And then you go in and it's the reverse. Now, all
32:01 these things together are not just sitting in a static way. They're gonna
32:05 an important role in the contraction But what it's showing you is the
32:12 structure of these mild fibers. All . It's showing you how the thick
32:17 the filament, thin filaments are gonna and it shows you that there's room
32:22 movement in there. If the thick the thin filaments have region where there's
32:28 overlap, that means they can create through this process of contraction.
32:35 there's other structural proteins in there. just mentioned them. You might get
32:39 question about this. You may but there's some other things. So
32:42 example, we have nebula nebula is protein that's attached to the Z
32:48 And what it does is it helps hold the thin filaments in line.
32:52 you can imagine if, if I had the thin filament, if I
32:56 had the act and they may go , they may go up. And
32:58 what nebula does? It reinforces the degree angle and so it ensures that
33:03 Acton travels at a 90 degree angle to the Z disc. All
33:09 this improves the efficiency of interaction. have a molecule called tin tin
33:15 is a molecule that looks like a . You can see it here being
33:20 . All right. If I stretch spring, it's gonna want to return
33:24 its original shape. If I compress spring, it's gonna want to return
33:26 its original shape. And what this , it allows a muscle fiber after
33:31 contraction to return back to its original . So you basically have springs inside
33:37 muscles. Okay. It's associated with M line. All right.
33:45 it's actually there and there's the it's associated with the Z as
33:48 All right. The next one is muscle or a fiber called dystrophin.
33:55 is a protein that ensures that the fibers or the myofibril up near the
34:00 have something to attach to. All . So, in other words,
34:05 you have the structure that is contained you are trying to create these interesting
34:10 works, there's gonna be a point there's no way to create that hexagonal
34:15 . And so that's what dystrophin It ensures that there's something that attaches
34:20 the sarcolemma and maintains the shape. then another one here is alpha 10
34:25 this helps to hold everything together at Z line. So that's basically the
34:30 of the Z line. All So the idea here is that we
34:35 these micros structures that are being maintained these myofibril to ensure an efficient interaction
34:45 what we're gonna do is we're gonna here and we're gonna stop talking about
34:49 for a moment because molecules are Right. I mean, some of
34:53 are sitting going, there's a lot alphabet soup in here and there's names
34:56 are scary and they're weird and I it all right. So what I
35:01 do is I want to back out I wanna take a look at how
35:05 muscle structure works. But before I , are there any questions about any
35:08 these names? A band, I H band M line, Z line
35:14 about those? Yeah. OK. . Uh huh. OK. So
35:23 M line is like the Z All right. So remember the Sarco
35:27 is defined by the Z line, M line sits in the middle between
35:30 two Z. All right. So is coming off the M line?
35:34 would be the thick filaments. So the Z line is where the thin
35:38 are coming, the M line is the other. It is in the
35:41 where the thick filaments are coming. that's basically they're pointing toward allowing them
35:45 filaments to point towards each other. I'm gonna steal her again for a
35:49 since you asked a question, she's front of you, right? So
35:52 she's the Z line and I'm the line, there's her thin filament coming
35:56 , there's my thick filament coming off that's allowing the interaction to occur.
35:59 right, you, so I'm not answer that directly. There is gonna
36:14 movement. All right, because if Sar Kamir, so the question is
36:18 the ze it's not do the Z or do the M lines move?
36:23 answer is gonna be ultimately yes. in order to get a contraction,
36:26 gonna be be bringing two Z lines to each other towards the M
36:31 All right, we're not seeing this because we haven't started talking about a
36:35 . We're just talking structure right All right. But yes, the
36:40 because it is the unit of That's the unit of the muscle.
36:44 we're gonna see is that to make muscle contract, you make the Sarker
36:49 and expand, shrink and expand. right, that's where we're going to
36:55 . That's where we haven't, we been there yet. Any other
36:59 These are good. Th this can't you everything I'm gonna say up here
37:03 always clear. Most of your sitting are never clear. So, all
37:10 . So what I wanna do is want to deal with a muscle
37:14 All right. So when we think how a muscle goes through a
37:19 remember it's an organ right? There many, many muscle fibers in here
37:24 I can list a whole lift a bunch of different things and I'm
37:27 I'm gonna impress you all by I'm gonna curl my my little pointer
37:32 , watch and be impressed by the of my muscle. You see
37:36 that weighs like what announced maybe two I can curl that. Ok.
37:44 I can also curl a chair. picking the wood chair because it's heavier
37:50 that one. So here you get watch and someone's gonna video this and
37:54 watch professor smack himself in the I've gotta do this this way.
37:59 right. So same muscle, same . How much does that chair?
38:06 £20.25. So same muscle can do weights and can they do big
38:14 right? And the reason for that because an organ, the muscle organ
38:19 made up of individual units called motor . A motor unit is what is
38:26 an alpha motor neuron. So basically neuron that innervates a group of muscles
38:34 . They can be of varying You could have one cell and one
38:38 . You could have one neuron in cells, one neuron in three
38:41 one neuron in 10 cells, one in 100 cells. A motor unit
38:45 simply defined by that alpha motor neuron the cells that it innervates. So
38:51 you look at this picture up here you're looking at the little cartoon,
38:55 can see there are two motor In this picture, we have the
38:59 motor unit and we have the blue unit. The red motor unit has
39:03 cells the blue motor unit has two . So in terms of strength,
39:09 all things being equal, right? muscle cell being equal. Which one
39:14 the more powerful motor unit? If had to guess red or blue
39:19 why more cells? Ok. So a real simple way to think about
39:25 , right? So you can imagine any sort of movement that I
39:29 I'm going to recruit in more and motor units if I need more and
39:36 strength to do the job. So when I curled my little
39:42 do I have a lot of motor ? No, I had probably a
39:47 to do the movement. And then I went to the chair, I
39:51 recruited those motor units to say, , we're gonna move something and they
39:55 I can't do it. And so happens is I recruit in more and
39:59 motor units until I can move the . All right. So motor units
40:06 these groups of cells plus that neuron we're going to be using to dictate
40:11 tell what those, tell those cells to do. All right. The
40:15 feature about a motor unit. a couple of things first, if
40:21 doing delicate activity, what do you delicate activity being if you, what's
40:26 surgery? Ok. That's, that's good one. Anyone here done surgery
40:29 I have to, I mean, had surgery but have, have you
40:33 surgery? So, I don't think lot of people know that one.
40:36 a good, it's a good Surgery is a really one, good
40:39 . What is a delicate activity that all do and that you're probably doing
40:44 now, writing right, using your to manipulate a pen or a pencil
40:51 a stylist to make very, very delicate movements. That would be an
40:55 of delicate activity. Course, activity the opposite. What would be an
41:00 , of course, activity. What's ? Weightlifting? That's a good
41:05 Weightlifting, but not everyone here but there is something we all
41:09 We all walk. What is Right? Walking is me lifting up
41:13 foot, right? I'm gonna lift my foot. I push my weight
41:17 and I stamp down like uh That's an exaggerated movement. All
41:25 Weight walking is literally not falling. you seen that? I mean,
41:29 what you're doing. You're basically catching before you fall. You know what
41:35 is? What's swimming, not That's right. Movement that prevents
41:40 There you go. All right. when you're dealing with delicate activity,
41:45 you're gonna have is you're gonna have , very small motor units, but
41:49 gonna have a lot of motor units . All right. So in other
41:52 , very few cells and what that allows you to be very, very
41:56 in the types of movements that you . All right. Course activity on
42:00 other hand, you're gonna have very motor units because you don't need to
42:04 that fine control. What you're just to do is you're trying to create
42:08 , a mass movement. That well, I, I want to
42:13 the word course, but you'd never course in a course definition. But
42:17 idea is that I'm, I'm doing things and so I don't need to
42:22 tune, lifting my foot up here here is not gonna change my
42:27 right? But if I have big movement, my writing is gonna be
42:32 weird. All right. So delicate , small motor units, mini motor
42:38 , course activity, big motor not as many. Well, you
42:43 have many as well. All the last thing I want to point
42:46 here is about uh clustering. All . So if you think of an
42:50 like the muscle, I mean, muscle organ, you don't want to
42:53 all the motor units on like one of the muscle organ. And the
42:57 for that is because when they all , what would happen is that the
43:00 would, would bend where all those units are. So, what you
43:04 to do is you want your motor spread out, right? And so
43:08 might have a little bit on the , a little bit on the
43:10 You'll have the cells kind of uh throughout so that you're getting a smooth
43:15 even movement in that muscle during a . So for example, going back
43:22 the simple thing here when I'm doing curl, the motor fibers in those
43:27 units are spread throughout that bicep. when I'm doing the curl, this
43:32 the direction see it goes like so , it's not doing this. If
43:38 had the motor units on one they might do this or they might
43:41 that with the muscle. All that's why it's spread out to ensure
43:47 smooth movement of that muscle. The sits where it sits because it's trying
43:51 create that movement in that particular Now, here's something that should look
44:01 . Does this look like something we learned in the last lecture? Looks
44:06 the synapse? Yes, we're gonna where it is. It's exactly this
44:12 why we learned about action potentials, ? This is what we have been
44:17 with, but we have a special for it when we were talking about
44:20 to neuron where we're dealing with two talking to each other. We called
44:24 the synapse. All right, a between a, a muscle cell and
44:29 neuron is given a special name. call it a neuromuscular junction. It
44:34 in the name neuro neuron muscle and junction is just the fancy word.
44:40 so it has its own nomenclature. We still have our synaptic knob,
44:44 still have the synaptic cleft and it , it's no different than what we've
44:48 before. Except with this down here a muscle and the region sitting underneath
44:55 synaptic knob. This region right here call this where all the receptors
45:00 we call that the motor end Now, is it much different than
45:07 we saw in the neuron? the, the, the real difference
45:11 is just in the number of vesicles the number of receptors. All
45:15 But that's again, not really I'm not gonna say how many,
45:20 many receptors are located in there. , that's unimportant. All right,
45:25 the same as what you've already We've just giving it new names because
45:31 where it's located. All right. when you see Nero muscar junction
45:35 OK. It's a synapse. what we're trying to produce in a
45:41 is a contraction. A contraction is an action potential. All right.
45:48 contraction is the result of an action . What is an action potential?
45:53 what we said? It is a , it is a message. So
45:58 we're doing is we're telling the cell to do. All right. And
46:03 what's going to happen is that in neuromuscular junction, we're going to
46:07 I mean, we're going to have potential, move down the neuron,
46:09 going to release the calcium that calcium going to tell the vesicles to open
46:13 . We're going to release the it's going to go across the synaptic
46:17 and it's going to cause what is an in plate potential. And that
46:23 plate potential is basically a graded potential results in an action potential immediately.
46:29 so powerful that it creates an action . And what's going to happen is
46:33 that a potential then travels along the of the cell. And when it
46:37 along the length of the cell, it's going to do is it's going
46:39 initiate a contraction. And so what little thing is trying to show you
46:44 is that relationship. So it look up here in the motor
46:49 right? So that's pre synaptic. can see here's the action potential,
46:54 potential here in the motor neuron is to precede the actual potential in the
46:57 fiber. Does that make sense? ? One response to the next.
47:02 you're gonna see one, the neuron gonna send a signal to the
47:05 So it has its action potential first then shortly thereafter, you're gonna get
47:09 action potential of the muscle fiber. right. So they're separate action
47:14 separate cells, one precedes the the potential and the neuron results in
47:20 an action potential in the muscle so , so good, right, a
47:25 results in another signal. The signal is not the contraction, this is
47:32 signal that's occurring in the muscle fiber results in the contraction. And so
47:38 can see here we have a period time between when the signal is sent
47:44 when the contraction actually occurs. Do see that? So the contraction is
47:51 result of the signal? Does that sense? Right? OK. The
47:59 is delayed because it takes a little of time for the signal to be
48:03 . Does that make sense? So that delay is referred to as
48:09 latency period? All right. And what we're seeing here. So here's
48:14 a potential action potential is going to over across the length of the
48:17 but you're not going to see a until shortly after that a potential
48:22 So you can think about this signal . OK. That's how that's kind
48:29 going. We have a period of that's called the contraction and then we
48:35 a period of time that's called And that should make sense. The
48:38 is gonna get smaller and then it's go back to its original shape.
48:43 this contraction and relaxation is going to different depending upon which type of muscle
48:49 looking at. You'll see differences. have fast twitch and slow, slow
48:53 muscles, but this contraction is referred as a twitch. Now, twitch
48:59 not this eyes up here on me quick. This is not a
49:02 Ok. You can be a twitchy but that right there is not a
49:07 , a twitch is not visible if , if you stimulate a muscle and
49:12 it to twitch. You will not the actual contraction. It's too
49:18 Now, if you take a the organ and create a contraction in
49:24 the cells, you would see the . But we're talking about an individual
49:28 , one cell out of hundreds of of cells. So you cannot visualize
49:34 twitch. It is a microscopic a microscopic contraction. Ok. If
49:44 look at a muscle and you send potentials at it like that, what's
49:51 happen is you'll, at each one those, you'll get a twitch,
49:54 . So you'll see one go up it'll come back down again. And
49:57 those twitches are close enough together, signals are close enough together. What
50:00 see is you'll see a slow rise the amount of tension. All
50:04 And this is a form of wave . I'm, I'm not summing action
50:11 . I'm summing a contraction. So the contraction, a twitch goes like
50:16 , right? And if I'm allowing contraction to occur, but before it
50:20 back into relaxation, I'm getting another so I can get another bit of
50:24 contraction. I'm increasing the amount of in that cell over time. All
50:31 . So that's what wave summation If the stimuli are far enough
50:36 what I'm going to get is an contraction. So that's what you're kind
50:41 seeing right here. It's like up down, up and down. So
50:44 can imagine at the end of at the end, instead of sustaining
50:47 , what you're doing is you're doing to the muscle. All right.
50:51 , it's wiggling. All right. want you all to sustain tension for
50:56 second. Everyone flex, make that , strong, strong. Right.
51:02 tension. Ok. What we're talking here is not achieving that. All
51:09 . That's the muscle kind of wavering trying to maintain that tension. All
51:15 . That's not the same thing as sewing machine legs. If you've ever
51:18 that, like you're trying to, legs get all wonky. That's,
51:21 different. That's just tired. That's . All right. Tetanus is a
51:28 and sustained contraction. So when you and held that tension, that's
51:36 When I sit here and sustain a to move an object that is
51:42 All right. Have you heard of disease? Tetanus? Like mom
51:47 don't go play without shoes out in , in the field because you'll step
51:50 a rusty nail and you'll get Have you ever had that explained to
51:55 or told you someone ever say that you? Yeah. Why it's called
52:00 is because the etiology, the, how that that expresses is you get
52:05 jaw l jaw. What's the muscle ? Sustained contraction? That's why it's
52:14 to as Tetanus. I hope you understand what I said. Sustained
52:18 Yeah. I'm not real sure what ideology of a cramp is. Uh
52:27 I mean, because you can get muscle that's gets into that uh into
52:32 tetanus state. But is it the thing? Maybe this is where my
52:40 falls apart once you start going into pathological stuff and that's what a cramp
52:45 . It's pathological, not like danger, pathological, just not
52:52 So I've already kind of mentioned this we're looking at a motor unit,
52:58 we're doing is we're trying to get sustained tetanus. So when I'm trying
53:02 do this, trying to do this of curl, what am I
53:06 I am creating tetanus. You recruiting motor units and I'm creating enough tension
53:11 move the object, right, to the load. If something becomes
53:17 In other words, that first motor is not enough to move the
53:21 then what I do is I recruit more motor units and that's what this
53:25 trying to show you. So when tried to pick up that chair,
53:27 can imagine. First motor unit nope, can't do it by myself
53:31 in another motor unit. Second motor . Nope, not enough, bring
53:34 another one, bring in another one I recruit in enough motor units so
53:38 I can ultimately move the load. the idea of motor unit recruitment.
53:48 a cockroach, it had to Sorry about that. I figured it
53:55 better than saying, oh, cockroach would have jumped. All right
54:03 you can imagine I have multiple motor and I want you to picture me
54:06 here and I'm having to hold something , oh, I don't know,
54:09 the chair and let's say I'm holding chair out to my side and you
54:12 an evil, evil person. And say if you drop that chair and
54:15 your arm, what I'm gonna do I'm going to blow you away.
54:18 gonna shoot you. And like it be very, very sad, but
54:21 is a cruel world and that's how works. All right. Now,
54:25 I do it with this, how am I gonna be able to hold
54:28 thing out out here like that Pretty much forever? I'm not,
54:32 have no fear of being, being , right? And the reason is
54:36 my motor unit that I'm using is fatigue, it's gonna tire out,
54:39 gonna use up its energy and it's say I can't do this anymore.
54:42 because I have more motor units, gonna happen is it's gonna say,
54:46 right, motor unit number one is quit. And what I'm gonna do
54:49 bring in motor unit number two and gonna keep doing the activity,
54:53 But if I'm holding a chair out I have so many motor units recruited
54:58 the fatigue is gonna set in and gonna happen is I'm gonna run out
55:01 motor units, right? And so ends up happening? Is, is
55:04 when I can't sustain the contraction then the muscle just says, rather
55:09 damaging, I'm just gonna let things . All right. So, fatigue
55:13 in essence the inability to maintain that tension. And that's a result of
55:20 of energy, et cetera, et , et cetera. All right.
55:24 your body does this through a process asynchronous recruitment, right? This is
55:31 like having a 24 hour factory with shifts, right? If I
55:36 I had a student a couple of ago, she was a uh a
55:40 a floor manager at the FRITO lay down in sugar land that made all
55:46 Cheetos in this part of the country 24 hours a day. It did
55:51 run full speed. She said they probably amp up or ramp up a
55:55 two and three fold, but it three shifts and that's what your muscles
56:00 like. It has multiple shifts. have your regular daytime shift, you
56:05 an eight hour evening shift and you another morning shift. And you can
56:10 all Cheetos all the time, my tension all the time, right?
56:17 if I ramp things up, I'm with the shifts and that's where the
56:22 comes from. So that would be asynchronous recruitment, just different shifts for
56:27 activities. And finally, the last thing here is that muscles will recruit
56:32 fatigue resistant muscles last. All All right. Sorry, they do
56:37 first because the rationale here or the behind this, as you can
56:43 your muscles have no idea what activity they're responsible for. They, they're
56:47 sentient, they're not like, well, this activity, um,
56:51 running activity we're doing is just a . Um, so we'll just burn
56:55 really, really quickly. It has idea. Am I running a
56:57 Am I running a sprint? Am being chased by a honey badger?
57:00 don't know what's going on. I've got to move until my brain tells
57:04 , stop moving. And so what gonna do is it's gonna do the
57:08 ones first in the hopes that the outlasts the fatigue. And then what
57:15 happen is once fatigue sets in, when it re brings in those quick
57:19 muscles. So, if you like when you burn through your muscle
57:24 you get your muscles get real tired the end, it's like really,
57:27 tired. That's why because of which are being recruited when. Ok.
57:36 right. I don't really talk a about this, but muscle tone or
57:40 on this, that much is to a, that's when you see the
57:44 and the cheesecake. Uh, basically, these are bodies that have
57:49 muscle tone and that's just a continuous passive partial contraction when we go and
57:54 . What we're doing is we're creating , the muscles are sustained or being
57:58 a slightly sustained contraction. And for , it demonstrates health. So
58:04 that's what we see is, this is healthy, this is a
58:06 body. That's why people with tone attractive to us. All right
58:12 tone is important for a couple of , posture, balance and preventing
58:17 All right, if you don't what's the likelihood that you're going to
58:20 yourself pretty good? If you get the sofa and say today, I'm
58:24 to run for the first time And you go outside, your muscles
58:28 kind of like, I don't know going on and they're not supporting those
58:32 and that's where you can get that . All right, typically low muscle
58:39 is associated with good flexibility. All . And then here high muscle tone
58:45 strength. Um Let's see, what do I want you to know
58:50 Um Nothing particularly important. Basically that the structure of the muscle. So
58:58 shape of the muscle is based on tone, the type of contraction that
59:01 does. Um And also the result physical activity. I never asked a
59:08 about this on the exam, but do want to point out something here
59:11 that every muscle has an ideal All right. And so that's what
59:16 graph is read uh is demonstrating is tone is important because it provides the
59:22 of, of ideal length. If bring the fibers too close together.
59:27 other words, the thick and the filaments get too close. They
59:30 they have a less opportunity to move , any closer. Right.
59:35 too close. I can't, I move any further. Right. So
59:39 want them to have a certain distance from the Z and the M
59:43 All right. If I pull them far apart, there's not enough overlap
59:48 them. So it's a lot harder them to actually pull on each
59:52 So, too close, problematic, far apart, problematic. There is
59:57 ideal or an optimal length. All . So the last little bit of
60:04 class, well, not the last . There's two other things we're going
60:07 deal with energy as well. And is we're going to finally come back
60:11 that question is, how do we about a contraction? All right.
60:18 there are three basic steps. The step simply put is what's going on
60:22 the neuromuscular junction. Second step is going on there at the triad.
60:26 step is what's going on inside the cell itself. What is creating that
60:33 ? All right. So the first we've already kind of talked about,
60:36 said, hey, uh neuromuscular what's going on? So you can
60:40 here's our neuromuscular junction, we're just to kind of walk through these steps
60:43 . So, neuromuscular junction, here's cell. There is the motor in
60:47 . This is representing the T Here, you can see the sarcoplasmic
60:52 , the region nearest the T we said it's called the terminal
60:56 All right. So the blue is sarcoplasmic partic. And then ultimately,
61:01 going to be asking the question, going on between the Acton and the
61:05 . So at the neuromuscular junction, potential travels down causes the opening of
61:09 calcium channels, calcium flows into the that causes the vesicles to open
61:14 releasing neurotransmitter. Neurotransmitter goes into the cleft in the synaptic cleft, that
61:21 is going to bind to its When it binds to that receptor,
61:24 going to open up sodium channels, rushes into the muscle cell. When
61:29 Russ rolls into the muscle cell, are creating a greater potential. We
61:34 a special name for it. We it the in plate potential. The
61:38 potential isn't powerful enough or strong enough result in an action potential. All
61:44 . So that's step one stimulation through uh neuromuscular junction act potential results in
61:52 action potential. That action potential that's is going to move along the length
62:00 the cell. It's gonna stay on surface. Remember that's where all the
62:05 are located. But we also have tubules where are the t tubules,
62:09 tubules bring the surface inward. And that a potential is not just going
62:14 travel on the outside of the it's going to travel down through those
62:17 tubules and inside those T tubules, now have these specialized receptors. All
62:25 , there's two different types. All , we have these DH P channels
62:31 we have these iodine channels. The P channels are going to be located
62:37 the inside of the T tubule. rine receptors are right next to them
62:41 they're associated with the sarcoplasmic reticulum. sure I did that right. I
62:47 afraid of something there. All So you can think about it like
62:52 . Here's your T tubule, here's sarcoplasmic curiculum. Give me your
62:57 So this is the association we have DH P receptor and we have the
63:01 receptor, they're right next to each . So an a potential is gonna
63:04 down through the T tubule, Basically opening closing channels and it's gonna
63:10 across those DH P channels, the P channels open up. And what
63:14 do is because they're associated with the I channels. They open up the
63:18 I channels. The rine channels are of the sarcoplasm curiculum. They're calcium
63:25 . And we, what did we Sarcos or curiculum does it holds
63:30 So when an a potential travels down the T tubule, it stimulates opening
63:36 these channels so that calcium can flow the sarco or the sarcoplasm, the
63:43 of the muscle fiber. So, potentials result in calcium finding its way
63:51 the cell. All right, if hiding it away I'm hiding it away
63:56 a reason. And so what that is the calcium now has a
64:00 It has a job inside the muscle . So what's it doing? What's
64:04 calcium doing? Well, calcium allows the minds and the Acton to
64:10 All right, it forms what is the cross bridge. So remember we
64:15 that thin filament, right, which three parts had Acton Tropomyosin. And
64:21 we had the little troponin, which a hinge, we have the thick
64:27 , the bias in head wanting to with the thin filament. But it
64:31 , why can't it Tropomyosin is in way. So we got to get
64:34 tropy out of the way calcium is allows us to move the tropomyosin out
64:41 the way calcium binds to that molecule troponin. The hinge. When calcium
64:47 troponin, it causes a change in shape of the troponin. It pulls
64:52 out of the way and when it troponin out of the way, because
64:56 bound up to the tropy and it the tropomyosin out of the way.
65:02 , it moves the trop amycin so the thick and the thin filament can
65:07 . So action potential results in potential action potential in the muscle cell
65:13 in the release of calcium into the . The calcium in the cell allows
65:19 the thick and the thin filament to how by binding up to the troponin
65:25 move the trop amycin so that the and the acting can interact. That's
65:31 we're seeing in this picture. this is a complicated picture taken from
65:34 much more complicated textbook. But that's it's showing you here is saying,
65:37 , see how all this stuff is the way. Here we get the
65:40 , calcium comes in, it pulls the stuff out of the way.
65:42 I can get the interaction and it repeats that calcium leaves, it goes
65:48 into place. So calcium is the to a muscle contraction. See the
65:55 and the thin filament are able to and create the cross bridge.
66:04 But it's not just a cross See when those two things interact,
66:08 going to pull on the thin the thick filament, remember we said
66:12 the two heads, right? Looks the weird boxer. They're like a
66:18 . One binds when it binds to thin filament, the thick filament pulls
66:23 the thin filament and then I can it go and then reset and then
66:28 again. I can repeat this as times as calcium is available. Problem
66:33 , is that I have to do reset process. The power stroke has
66:37 steps to it, right? Think you pulling on a rope if I
66:42 a rope and I bring it to and I want to pull the rope
66:46 . What do I have to Do I have to let go of
66:50 rope. If I let go of rope, I can move my hand
66:54 and I can grab and I can it again. Now, obviously,
66:57 one hand, it didn't work. if I have two hands, I
67:00 do it like this. And this kind of what's going on here.
67:03 like the thick filaments. Here's a filament madge. I know. It's
67:08 . I don't have a rope but I have a rope. I'm
67:10 I grab and I pull and I and I pull and that's what we're
67:14 . That's what's causing the contraction, filament binding, the thin filament,
67:18 it, letting it go and pulling again. So this is the power
67:23 . So, how does this Well, you've probably heard your entire
67:27 that energy is important for a muscle , right? Energy in the form
67:31 A TP is important, but it's causing the contraction. What's causing the
67:36 ? What did I just tell you causing the contraction? Calcium good.
67:41 , calcium causes a contraction. A is involved, but it's not involved
67:45 the actual contraction. What's it involved ? Well, let me tell you
67:49 little story here and let's see if can kind of picture it out.
67:52 you ever heard of this of rigor ? What is rigor mortis dead body
67:57 ? So that's why we call it . So this is what happens when
68:02 TP is available. What it does it resets the position of the thick
68:09 . All right. So remember the and head binds to and pulls on
68:15 thin filament. If I'm in this , I can't pull again. So
68:18 have to first separate myself away from thick filament or from the thin
68:24 That's what A TP does. And what ATP also does is when I
68:29 the energy I recock and I set up ready to bind again.
68:40 No, it's real energy. What is is again, the energy is
68:44 transferred to change the shape of the . The molecule is in a shape
68:48 it can't do anything. And so a TPS energy does is it allows
68:51 to disconnect and reshape yourself so that in the cocked position. All
68:59 Now let's go back to the rigor to see if this makes sense.
69:03 ahead. Yes. So we're gonna it all together. So I
69:11 I will paint the picture for But let's deal with the rigor mortis
69:14 . You know, rigor mortis occurs death, right? A person
69:19 And what happens is is that the that hold the calcium inside the cells
69:25 no longer present. So, calcium out of the sarcoplasm curiculum and goes
69:29 the muscle cell. What do we ? Contraction is dependent upon calcium?
69:34 muscle begins to contract and because there always about 100 mo molecules of a
69:38 in the cell. You can see what's going to happen is, is
69:41 going to break the bond and basically a contraction to go da,
69:45 da, da, da, da and maintain the tension. And
69:48 I run out of a TP. so what I now have, I
69:51 a muscle in tension. So you imagine you have someone who's died or
69:57 organism that's dead. And then what is you get rigor mortis and it's
70:02 a stiff contracted state because there's no TP to allow for relaxation to
70:09 You're stuck in the contracted state. gonna show the picture here. We're
70:15 look up here at the picture, at the graph. All right,
70:19 we can see we're in the attached . A TP comes along, breaks
70:22 bond if I break the bond or off the phosphate, you know,
70:27 other words, release the energy, , I'm recock the molecule and now
70:33 stuck in that state and then I when I bind, I get the
70:37 . So there's the contraction and now stuck. So I have to wait
70:41 a TP to come along to So that's what this whole cycle refers
70:46 and resetting the A TP. Now, can I bind the
70:52 the thin filament with thick filament if no calcium? No? All
70:58 So the first thing I need is as long as calcium is present,
71:02 can go through the power stroke All right, I bind up to
71:06 thin filament I contract and I let and I repeat the process as long
71:11 A TP is available. So the things need to be available. Calcium
71:15 allow for the binding A TP. allow me to break the binding and
71:20 the shape of the molecule. I'm go back to the rope because I
71:24 that look on people's faces like I'm sure I'm getting this if I'm pulling
71:29 the rope and I'm just imagine I'm this two handed. If I'm pulling
71:31 the rope in order for me to on the rope again, what do
71:36 have to do? I have to go, don't I? So that's
71:40 the ATP is allowing is allowing me let go and move my hand.
71:44 this is what A TP allows. , I can't grab the rope unless
71:50 is available. So the two things to occur. I have to have
71:54 there so that I can have the and I have to have a TP
71:58 to make sure that I break the and reset the thick filament.
72:06 Mhm That's a perfect way to I used to use the example of
72:18 a trigger on a gun but that a couple of people. So,
72:21 it's the same thing, right? doesn't fire unless the, the hammer
72:26 . Right. And that's what this doing. It's cocking the hammer.
72:30 even looks like it. Right. then it pulls and that's when the
72:35 fires and I can't fire the gun until I talk the hammer one more
72:41 . So this is the process that's on inside the cell. Calcium is
72:47 to allow for the binding. HP necessary to reset the mycin head for
72:54 contraction. One of those two elements missing, you're not going to get
72:58 contraction. Now, what is the then? I mean, we've been
73:04 contract. Well, that's when we back to the saram me. All
73:07 , the saram remember is the unit contraction. What you're doing is you're
73:11 the Z lines towards the M right? So if I'm the M
73:17 and here are my little tiny mice heads, they're pulling this direction,
73:23 ? And it's saying that thin filament is attached to the Z lines,
73:27 gonna pull them towards that M line I'm gonna make that whole sarcomere
73:32 And if a muscle cell is made of hundreds, if not thousands of
73:35 mees, this is occurring in each the sarcomas and that's how the muscle
73:38 contracting. And in the process, we're gonna do is we're gonna change
73:43 , the length of those lines. , in doing this, I'm gonna
73:47 you by having someone come up here help me. All right. So
73:50 always my awesome helper. So you're , really? Do I have to
73:54 this? Yeah. Come up here quick. All right. So he's
73:59 be my Z line. All So remember I, what I'm doing
74:05 I, if I'm the M I'm a thick filament. You are
74:07 thin filament, right? So you see this right here would be the
74:11 this right here is a, this there is, I, do you
74:15 that? And it's going to be both side? All right. So
74:18 a contraction, the thick filament is on the thin filament. So I'm
74:22 and the Z line starts moving you can move right. So
74:26 we've moved closer together. What has to the I band or certainly
74:30 the, the, the H has it disappeared? Has it gotten
74:36 ? Remember I band or the H is here? It's gotten shorter,
74:39 it? What about the I Has it gotten shorter? Yeah.
74:43 what about the A band? Has gotten shorter? No, it hasn't
74:48 my arm hasn't gotten any shorter. arm hasn't gotten any shorter. So
74:52 happened during this contraction is that we the distance between where the end of
74:58 thin filament is and where the end is has decreased and where the end
75:03 the thick filament and the Z line decreased. So, in looking at
75:08 and you can sit down because you want to write this down what we
75:13 seeing in a contraction, a band the same length. But the I
75:20 the H get smaller. Alright. fibers themselves do not shrink.
75:29 When he moved closer to me, arm didn't get smaller and I had
75:32 arm didn't get small, they stayed same length. All right. So
75:36 we call this is the sliding filament . Now, it's not a
75:41 it's just what is named. All , the sliding filament basically means the
75:46 filaments are sliding against each other because thick filament is pulling on the thin
75:51 . And so the two Z discs either side of the M line are
75:56 towards the M line. And then the muscle relaxes, the Z lines
76:01 back to their original positions. the opposite of a contraction is
76:11 The way this happens is we just everything back into its place when I
76:16 the acetylcholine from the neuromuscular junction, ? That I have acetylcholine, that
76:22 the ne neurotransmitter of the muscle. have that enzyme. It's called acetycholine
76:28 . And it's the one that sits and goes, oh, acetylcholine,
76:31 gonna chew it up as it's being . And so what we're doing is
76:34 getting rid of that signal as fast it's being released. So that's number
76:38 . So get rid of neurotransmitter is first step and it's going to be
76:41 through the enzyme. All right. thing, the sarcoplasmic curriculum has a
76:47 associated with it. If I'm always to move calcium out of the cell
76:51 hide it in the sarcoplasmic curriculum, need a pump to do that.
76:54 pump is called circa. It's, can see smooth endoplasmic curriculum. Calcium
76:59 is where, where the name comes and all it's doing is it's always
77:03 and so it's always using a So there's another reason why you have
77:06 TP. So basically, as calcium being released, there are pumps in
77:10 to start moving the calcium back inside sarcoplasmic reticulum. So if there's no
77:15 potential, there's nothing causing calcium to released. So the movement of calcium
77:20 towards the sarcoplasmic reticulum instead of towards cytoplasm. So that basically the inside
77:26 the cell is calcium free, no , no cross bridging, right?
77:31 finally, that, that's what that little bit is. No calcium.
77:35 you're basically interfering or preventing the interaction the acting and the myo. So
77:41 we turned on, we've turned off we have something in place to ensure
77:47 everything returns back to normal. We the enzyme and we have the pumps
77:50 ensure that happens. And then with A TP that A TP present,
77:54 basically resets the mycin into a position that it can rein interact as soon
78:00 calcium becomes available. So I'm going pause there because I mean, the
78:07 of this is energy and it kind goes together. And so there's three
78:10 and so I might as well end here. I know this stuff seems
78:14 complex and complicated. The easiest thing do when studying this is just write
78:20 out. The first half of this was basically just definitions, right?
78:26 so here what it is is when were kids, did you ever play
78:30 game? Mousetrap? No, it's Rube Goldberg machine. Basically, you
78:35 at one end and there's something in end. Just go through the
78:38 What happens at step one? What at step two? What happens at
78:41 three? You'll find that this lecture on one piece of paper. It's
78:45 straightforward. So write it out for and explain to yourself as you're going
78:49 and it will make 100% sense. a great spring break. Good luck
78:54 your tests on Thursday. Notice how put them in the right
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