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BIOL 2301 Human Anatomy & Physiology I - BIOL2301_lecture17_1024
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00:02 All right, good morning campers. Today, we're gonna do a couple
00:07 different things that we're kind of like be hopping from subject to subject to
00:11 . We're gonna start with uh the cells and we'll move and talk about
00:16 uh really neurogen generation, ho how go about um uh organizing circuits in
00:23 , in the brain and the or the central nervous system in general,
00:27 we'll uh move from that. We'll of talk about circuits themselves, move
00:31 reflexes and then jump into the spinal . And it is kind of weird
00:35 normally most textbooks start with the uh cerebrum and they work downward to the
00:40 cord. Your book is backwards, goes from the cere or it goes
00:43 the spinal cord and works up to cerebrum. So I don't know why
00:47 chose to do it that way, it's just easier than trying to flip
00:50 around just to follow the book. our starting point here are going to
00:54 the glial. So we, we these up before we said that the
00:58 system consists of two basic groups of . We've talked about the neurons,
01:02 are the quarterbacks. They're the interesting . So we spend all our time
01:06 about them and then we got to that quarterbacks don't look good unless they
01:09 a blocking line receivers to catch the and running backs to run the
01:13 And so that's what the glial cells . If you don't like, my
01:16 metaphor is tough. It's the fall it's football season. All right.
01:20 these are the support cells. Uh are collectively referred to as glial cells
01:25 neuroglia, which is a weird If you look at it, it
01:28 like neuroglia, but I don't some British person probably pronounced it once
01:32 everyone just kept doing it that All right. So it's neuroglia.
01:36 the neuroglia, there are six basic . Um two are located in the
01:42 nervous system and we'll just gloss over very quickly. The other four are
01:45 the are in the central nervous All right. And so this little
01:49 right here, just kind of where picture kind of shows you the four
01:51 the central nervous system, the append , the oligodendrocyte, the racy the
01:56 over in the peripheral nervous system, cells and Schwann cells. Uh you'll
02:01 hear these referred to as neurol So you can see it over here
02:04 neural. Um and in terms of, of why I kind of
02:10 to them as you know, oh, they're the line, they're
02:13 rest of the football team is, this ratio right here. So
02:17 the star of the nervous system is neuron. That's where all the fun
02:21 happens. But they're outnumbered 10 to by the glial cells. So your
02:26 is mostly glial cell by volume. right. So um they're very,
02:32 important. Why? Well, they play a role in signaling. What
02:36 do is they support the neurons, create the environment in which the neuron
02:40 . They create the framework and the on which the neurons are established,
02:45 help maintain the system. So this why they're so important. OK.
02:51 so we're gonna just gloss over them everyone else does and we're just gonna
02:54 of list through them and say this what it does, this is what
02:56 does, this is what it We're gonna move on. All
02:58 So what we're gonna do is we're start in the central nervous system and
03:01 gonna start with, oh I guess . We're gonna start with the,
03:04 precursor cell. All right. So oligo uh progenitor uh sorry, the
03:09 inside pregenital, this tells you where coming from. All right. So
03:14 , these cells are capable of differentiating a whole bunch of different types.
03:19 typically we think of them in terms the oligodendrocyte, um they are able
03:24 identify their surroundings and it teaches them because they're able to identify their
03:28 they're able to grow where they need grow. They have these uh unique
03:33 that are called growth cones. We're to talk about that a little bit
03:36 . And what they do is when , the growth cones are formed to
03:39 , they're basically uh forced to go they uh are supposed to go and
03:43 they wrap themselves around all the uh and create the uh myelin that we're
03:49 in. But they can also play role in creating neurons. They can
03:53 a role in creating astrocytes. And , this kind of shows you the
03:56 potency. All right, pleural potency means the ability of one cell to
04:01 many different types of cells, So this is something that would occur
04:05 on in development and then go I'm gonna differentiate this way, differentiate
04:09 way or differentiate this way to become of these types of cells. But
04:14 , so we live, we use to kind of leap into what is
04:16 oligodendrocyte. And we've talked about we said, hey, myelin is
04:21 stuff that's wrapped around a neuron. serves as insulation. And so what
04:25 does allows for the speed of an potential to increase by jumping over these
04:31 of, of uh myelin. And oligodendrocyte is a cell that is the
04:37 in the central nervous system. And you can see here this is kind
04:40 what it looks like. Um The thing is is that these cartoons will
04:45 give it justice so they can uh up to about 50 different Axons at
04:50 time. So Oligo means mini. Oligo, Denro, Oligo mini branches
04:57 where, where the word comes All right. So uh not only
05:02 they support and create the network or the environment through which the AXON is
05:07 to be travel, uh It does , but in addition, what it
05:11 is it release a growth factor or inhibiting growth factor that says,
05:15 um we don't want you to grow . And so one of the reasons
05:19 neurons are incapable of multiplying and dividing because of these cells releasing these chemicals
05:26 prevent that growth. So once the system kind of establishes itself, it's
05:31 established, it doesn't change uh in of the neurons. All right,
05:36 gonna see that it's gonna change in of the connections, but where the
05:40 actually are, that's one of the here. All right. And then
05:45 course, um as I as I , all of these cells are going
05:49 play a role in regulating things. not going to go into the details
05:52 what it regulates, but it helps control neuronal function as well. So
05:58 of the show neuron, many other playing an important role telling what the
06:03 what to do. Now we're going jump out of the central nervous system
06:07 quick, go to the peripheral nervous . All right. So this is
06:11 one cell of the neural lite. put it here because it's like the
06:14 Denroy, the difference is in All right. Whereas the Yod Denroy
06:19 a cell body and then many extensions wrapped around each of the individual
06:24 Here, the s swan or the I one cell will wrap itself multiple
06:30 50 to 100 times around an And then that's that myelin sheath.
06:35 then the next one is another neural . And the next one is another
06:39 lite creating the uh series along the of the axon, which is what
06:44 being shown here. So each of are an individual cell. All
06:48 Now, what's interesting about these that want to point out apart from the
06:52 and uh increasing the rate at which action potentials travel down that neuron is
06:59 if you were to damage a uh as long as it's within the
07:03 of the axon and not near the body, uh what will happen is
07:07 that uh you'll lose that axon and Schwann cells kind of unravel themselves and
07:12 send out factors that say, this is the way you need to
07:16 and they kind of serve as the through which an axon will regenerate
07:22 If you damage it now, the of regeneration is really, really
07:26 So if it doesn't do it quick , if it's too, too close
07:29 the cell body, you'll end up all sorts of problems. You may
07:32 even uh regenerate back to the right . But if you like say damage
07:37 here, then regeneration is not very to do. And I can't remember
07:42 the distance is, but that's what is trying to tell you is,
07:46 , you can regenerate neurons in the nervous system under certain circumstances. And
07:53 because these cells, the neurolite or cell releases the factor. Tell that
08:00 axon where to go. OK. to the central nervous system. All
08:08 , we call astrocytes, astrocytes because discovered in Houston. I, I
08:16 woke you all up. Now, not why, why do we call
08:18 astrocytes? They're star shaped. That's, that's the reason. And
08:23 was disappointing last night, wasn't Yeah. Some people you don't even
08:27 to talk about it. Yeah. , don't tell people that. All
08:34 . Yeah. They're all like, some people are like, what's going
08:36 ? Yeah. Astros lost last We would have gone to the World
08:39 again, but we had to let rangers do it because they've never
08:45 Did you go last? Not to World Series? No. All
08:52 Anyway, Astrocytes most abundant star shape job is to create the network on
08:59 neurons live. All right. In words, they're the scaffolding.
09:02 if you don't know what scaffolding if you go to any building that's
09:05 built, like the one that's over the west side of campus, you'll
09:09 all this structure on the outside that workers are climbing up and down.
09:12 scaffolding. All right. So that's of what we're saying is that these
09:16 are kind of sitting in there hey, I'm gonna hold everything in
09:19 and this is how the a or uh the neurons are gonna be
09:23 right? So that's their kind of of their primary job. Their secondary
09:27 is to control and create the extracellular , not create but maintain the extracellular
09:33 in the proper balance. So their is to create the environment to maintain
09:38 environment of the uh central nervous Another thing that they do is they
09:44 responsible for creating the blood brain barrier with the capillaries, they tell the
09:50 what to do and then uh they up the glucose and they store up
09:55 for the brain. Now they don't a good job of storing glucose.
09:58 mean, when we say store it's not like the liver, which
10:01 does a really good job. It's like your muscles which do a really
10:04 job. It's not like your which does a really, really,
10:07 good job by converting glucose into All right. What it does,
10:10 takes up the glucose and holds on it and then releases it to the
10:14 as needed. So it holds a , very small portion of glucose.
10:18 right. But it is responsible for those nutrients to the neurons. Those
10:26 don't get the those nutrients directly from blood. Um It plays a
10:31 Let's see if I have it up . Oh, yes. Access scar
10:35 . Um I may have mentioned this this class. Maybe it was in
10:38 other class that I teach. Um had a student once after class
10:42 hey, after I gave this hey, um when I was younger
10:45 three years ago, that's what he . Um I got hit in the
10:50 with an ax. Yeah, I . And you're like, and you
10:54 and he's like, yeah, he , so what happened to that
10:57 You know, what happened there? I'm like, well, my best
11:00 not being a physician is that when neurons died away, that space filled
11:06 with scar tissue. Now, what of scar tissue astrocytes? So it
11:11 , it's not an empty space where the neur nes died. They kind
11:14 fill in that space. And now neurons have to work their way around
11:18 through crate networks around that portion of tissue, right? Because these do
11:24 play a role in sending signals. job is to, you know,
11:29 of allow the neurons to do their and to act as that scar
11:34 So they kind of serve also as way to repair things. They also
11:40 as a macrophage. In some they'll take up the damage, um
11:45 talk to other cells and tell them to do. And so this is
11:48 that last line is. So they have multiple roles. And so
11:52 key thing here is they create the in which the neurons work. All
11:59 . So whether it be the chemical or the physical environment, that is
12:03 role of the neuron or sorry, brain just turned off. All
12:09 Um I'm going to jump back This is not on your slide.
12:13 just go back. All right, I don't have a slide for the
12:16 cell. All right, the satellite is the aster side of the peripheral
12:21 system. That's all you gotta All right. So just like the
12:26 the neural Limy or Schwan cell is oligodendrocyte of the peripheral nervous system.
12:30 satellite cell is the astrocyte of the nervous system. We don't see them
12:36 throughout the peripheral nervous system. They're located in the ganglia, we'll talk
12:40 the ganglia later. Um But as as you think, oh, they
12:44 of build structure and help support the , then you're probably in good shape
12:49 that, which is why I don't a slide. OK. All
12:55 Back to central nervous system, the cell, we've already talked about
12:59 the ependymal cell, this is a of them. You can see right
13:03 , that little line of cells right . Here's the cartoon, you can
13:06 the cilia, their job is to those internal cavities. So the
13:10 their job is to make cerebral spinal , all right. And so they
13:16 fluid from the blood and other materials the blood and they make that cerebral
13:21 fluid. Um they um are permeable to allow that to happen. And
13:27 really all their job is. There's little bit more to it. But
13:30 think for our purposes, that's probably enough. All right. And then
13:36 we have the microglia and there's a more to these, these are a
13:39 more interesting and because it has gotten textbook shift, we're not going to
13:43 with it, but in essence, kind of serve as macrophages. All
13:48 . They kind of hang out and not doing anything for most of the
13:51 because macrophages, you don't want them around just chewing things up. So
13:56 just kind of sit there and kind do nothing. But if damage occurs
14:00 something leaks into the ner nervous something that's not supposed to be
14:04 they elicit an immune response, they activating, they move around and they
14:09 destroying foreign tissue or foreign uh materials damaged tissue and then they were,
14:15 , they remove that so that repair take place? All right. So
14:20 what this is. They serve as of an immune defense cell. All
14:25 . And they are related to the . They are not actually,
14:29 a nervous cell per se. They're of an immune cell. So,
14:35 , um, they actually, they more roles, like I said,
14:39 , when you start reading up on , if you ever go and read
14:41 on them, you'll be like, , they actually do a lot
14:43 they can kind of serve as a cell. Um They're really important during
14:48 uh um s stroke as well as um um concussion type damage. All
14:58 . So those are the six they're basic. If you're gonna get
15:01 question, it will be like which the following cell is responsible for making
15:05 spinal fluid, that type of So it's pretty straightforward type of uh
15:10 here. What I wanna do is , I just wanna briefly uh describe
15:16 function of the nervous system. All , because what we're doing now is
15:19 , we're, we're kind of edging way into this larger structure that will
15:24 very, very complex. And part the reason it's complex is because I've
15:29 this before is we like to put in a bo things in a
15:32 right? It's like here's something I want to label it and I wanna
15:35 done with that label, right? this is a system where things fall
15:40 boxes. And so they're kind of out all over the place. And
15:44 I wanna kind of point out that gonna try to keep it as simple
15:47 possible for our purposes. All But as you move on, if
15:50 go on into and become a you're gonna find out there is more
15:55 this than what I taught you. right. So in terms of
16:00 um it's responsible for a whole bunch things. So we are going to
16:03 information from the external environment and the environment of our bodies and we're going
16:07 process that information and then tell our how to respond to that information.
16:12 right. So this is the primary that the nervous system is responsible
16:16 All right. And so this is we refer to as integration. All
16:20 . So we're going to process the and then an outcome is gonna be
16:25 based upon what we receive. So example, if I step on a
16:29 , I'm not gonna sit there and . Hm This is a uh interesting
16:33 at the bottom of my foot. do I do here? There is
16:36 very often things that are programmed, that are memorable, things that are
16:40 instinctual that I can't quite fathom I'm not sure how that stuff is
16:46 , but it's preprogrammed in our how to respond to stuff. How
16:50 we know this? Have you ever a newborn baby? And you look
16:54 a newborn baby and you give them look like, oh, this is
16:57 cute and you give them the right? And what does the baby
17:00 that? Smiles back. And some are, well, that's just
17:03 No, that is an instinctual All right. And it's one of
17:08 reasons that babies are kept alive because really hard to kill something. So
17:11 . That smiles back at you. though they poop and cry all the
17:15 and keep you up all night. do that. It only lasts two
17:19 three years. It's no big I got four. Then they go
17:26 high school. All right. So do we process that information? What
17:31 we do it? The one we store it away. All right.
17:35 . What we can do? We act on it immediately. So
17:37 you the stepping on this tack, do I do? There's a reflex
17:40 . I'm gonna lift my foot. that's acting immediately. The third thing
17:43 can do is I can ignore I'm not gonna ignore the tech in
17:45 bottom of my foot. All All right. So all of this
17:50 that we're talking here is occurring at level of the neuron. All
17:55 So we're talking, processing, we're about neurons are creating signals in response
18:01 signals in response to signals. All . And this, it's all done
18:05 a network at the level of the . We're not storing up information like
18:10 rolodex. It's patterns of neurons firing create these different types of responses which
18:19 going to get to in just a . All right. So what are
18:23 gonna be stimulating? Well, uh neurons are gonna stimulate muscles, glands
18:27 other cells. And so this can done both at the conscious and at
18:31 unconscious level. All right. So you eat food, you don't have
18:35 tell your digestive system. Hey, please start digesting that food. All
18:40 . That would be an unconscious thing the body detects the food, a
18:45 and a scent that actually causes the to begin digesting, right? But
18:51 are things like if someone throws you ball that you lift your hand
18:54 that would be a conscious. So are motor neurons that are sending the
18:58 outward. Sensory neurons are sensing are the signals inward. And then there
19:04 the weird stuff that we're not going go into a lot of detail
19:07 Um if you're ever interested in I encourage you to take Doctor Zera
19:12 class, which will go into much detail, but in essence, generating
19:16 . This is your self-awareness. I . Therefore, I am all
19:20 This is the cool part, think your brain and then think about your
19:23 , thinking about your brain. That actually what's going on. All
19:27 And it's just like what? Yeah, I think it's cool.
19:31 right. Um Perception of senses right . Is this room bright? Let
19:36 ask these people who are right there the light. Is the room
19:39 Yes. All right. And you're this way because it's too over
19:42 Oh, wait there up there. where it's bright. I feel bad
19:45 them. OK. Right. That's perception. All right. And perception
19:51 an awareness of the environment around I'm gonna just kind of do
19:57 It's gonna sound really, really It's not. All right. Is
20:01 world around us as, as we it. What do you think?
20:08 mean? So in other words, this reality you say? Yes.
20:13 right. I'm gonna show you that not OK. Uh How many here
20:18 detect uh radio waves? No, can't. Uh How about UV
20:26 Can you detect UV light? How infrared light? No, no.
20:33 do those things exist? Yeah. the world what we perceive is our
20:39 . All right, there are things of our receptors. So we have
20:44 receptors that allow us to perceive our . Now, just to prove that
20:49 things are things that are perceptible. bees use UV light to find the
20:55 to be able to get their pollen their nectar really get their nectar um
21:00 their honey. All right, rattlesnakes other pit vipers hunt using infrared
21:07 They have a receptor that detects in infrared range. We do not detect
21:11 those things. And in fact, whole visual spectrum is part of a
21:16 electromagnetic spectrum that includes x rays and waves and microwaves and all the other
21:21 stuff. So, your cell which is part of the electromagnetic spectrum
21:27 we talk about Wi Fi and Bluetooth Gigahertz and stuff like that. Ig
21:32 know, that's scary stuff. That's an electromagnetic spectrum. It's in the
21:36 spectrum as our visual spectrum. We have receptors to detect it yet it
21:42 . So there are things that are there that we can't perceive, but
21:48 can create things that can perceive All right. So perception is how
21:54 understand the world around us. We have language, that's how we
21:58 that's going to be done in the nervous system, your reasoning, your
22:01 , your emotions, these are all that are a result of the neurons
22:06 in information receptors, receiving information, processing information and then having some sort
22:13 outcome, some sort of output from processing. This is all done at
22:18 level of the nervous system. Now we get a nervous system? This
22:23 far more depth than I that I to talk about here. I
22:27 I I bring this up just so you understand that the brain forms in
22:32 very unique ways. All right, kind of go through two stages of
22:37 . All right, your first stage development is early development, that would
22:41 uh embryonic development. And when that , when the brain forms, it
22:45 a different form of, of neurogenesis neurogenesis simply means how we make our
22:51 . All right. So it uses is called radio. So the brain
22:55 outward instead of around. And then you are in puberty through about y'all's
23:03 right now, your brains are still through a second metamorphosis. And this
23:08 be where you use tangential. why do I bring this up?
23:12 , because these neurons don't just magically . All right, they're not like
23:16 new brain. What happens is is are migrating to get to where they
23:22 to go and they do so first establishing the structures of the brain,
23:27 is what you see up there in embryonic. So you're going to
23:29 for example, in the cortex, are multiple layers and that's what's being
23:33 there, there's six layers and that's it's showing you. And how do
23:36 get those six layers? What basically outward in a radial fashion. And
23:40 once those layers are established later, you're restructuring your brain, you're gonna
23:45 within the layer that you're found. neurons move along their, their tangents
23:52 in those specific layers and that's what seeing there. All right. And
23:57 way they know where to go is the other cells, those glial cells
24:01 telling them where to go, specifically astrocytes. And I think this is
24:08 cool picture if you like. So not the direction I want to
24:12 That's the cool picture. Now, probably looking at this. I could
24:15 less what this is. But you , I'm a biology nerd. So
24:18 like this make me excited. What looking at here is what is when
24:23 saw that oligodendrocyte progenitor cell, we it had these little tiny extensions.
24:27 is what it is. All this is a growth cone and these
24:32 tiny things out here are extensions of c the cytoplasm and the plasma membrane
24:38 out feelers with little receptors on it the growth cone which way to
24:43 So the green and the red represent microtubules and the intermediate filaments that are
24:49 the length of that structure. So is a you, this is just
24:53 little tiny tip of that thing as going around. Now. What's it
24:58 ? Well, it's using a process chemotaxis. Chemotaxis is simply how a
25:05 receives a chemical signal to tell it to go. All right, your
25:10 system. Have you ever been bitten a mosquito? Does it swell up
25:16 get all? All right. So that swelling occurs, what you're getting
25:20 localized edema and you're getting immune cells are attracted into that area. All
25:27 . So that attraction to get those cells into the area is through a
25:31 of chemotaxis. All right. So is not something specific specific to the
25:36 system. This is simply a way cells tell other cells where to
25:41 All right. And what these neurons doing is they're doing a feeler system
25:45 it's like here, I've got my and it's like, oh, you're
25:48 me to go this way. So grow up this way. Oh,
25:50 supposed to grow this way. So start growing that way and you just
25:53 following it if this doesn't make sense you. Um You guys ever watch
25:57 Week on Discovery Channel? I I mean, I know you guys
26:01 watch TV anymore. It's all if not a, you know, tiktok
26:05 video, but go watch sharks attack tiktok. All right. The way
26:12 sharks know where their prey is is to Chemotaxis, right? They can
26:18 chemicals in the water or they can a flailing fish, a wounded
26:24 And what they'll do is they'll beeline that, that, that um,
26:29 structure, that fish or the but they don't like beeline directly.
26:33 do they do? And it's really that you can drop a chum in
26:35 water and you watch shark, it'll it and what they'll do is,
26:38 start swimming in these wide berths trying find the thickest signal and then it
26:45 start getting closer and closer and And finally, that's when it goes
26:50 , that's also how sperm find They basically swim around like this.
26:58 . I mean, that's, that's . They just kind of wiggle like
27:00 and then they get the detection, chemical signal that comes from the ovum
27:04 then they start doing this really wild . It's kind of like Elaine from
27:10 , if you've ever seen the Elaine , OK. It's crazy. And
27:15 kind of the same thing that's going here. So this is a cue
27:18 attract neurons. All right, sometimes can send a signal to repel as
27:24 . Say don't grow this direction. just want you to grow in this
27:27 direction. All right. And so can get branching so you can get
27:31 neuron that's growing, can actually create branch, you can do other things
27:36 you can alter its sensitivity. And what we're talking about here is that
27:40 brains, even though they go through two periods of development, they're still
27:47 of changing the structure of the Alright. And this is what we
27:54 to as neuroplasticity. All right. when you hear plastic, don't think
28:00 think changeable. OK. That's what means. So a neuroplastic brain is
28:07 brain that is changeable. All Now, this is where we have
28:13 kind of think differently. All and I've already mentioned this before,
28:17 I want you to kind of incorporate in. So over here, this
28:22 be the each of these dots represents neuron and a line between them represents
28:27 connection. So some sort of synapse those neurons. All right. So
28:33 is how you would start off All right. So all the neurons
28:37 in place, some of them are to each other, right? And
28:40 talking to each other. Great, ? But as you go through life
28:46 things happen and you experience things, that's gonna do is that's going to
28:51 the neurons to start trying new So what it's gonna do is you're
28:56 create new synapses. Now, some these synapses are useful, some of
29:00 are not. All right. So is part of the plasticity. It's
29:04 , oh, here I am, a neuron and I'm not talking to
29:08 , but maybe I want to try to this cell for a little
29:11 Oh, it doesn't work out. going to pull it away. I'm
29:13 to try talking to this cell for little bit. Oh I'm going to
29:17 a stronger connection. And so that be what's happening here. So you
29:22 see here is the original network of and who they're talking to here.
29:27 creating the new synapses and you can seeing that these cells now are talking
29:32 frequent with each other and these cells talking less frequently. And then
29:37 what ends up happening is you create completely new network of interactions. This
29:43 how the nervous system remembers things, , information creates skills, right?
29:52 when you learn how to ride a , what you're doing is you're creating
29:56 new network and then as you become and better at it, your brain
30:01 is making that particular group of interactions and more efficient. So there is
30:07 interference. This is why practice makes , right? Because what you're doing
30:14 you're creating these networks that are Well, as perfect as they can
30:20 . OK. So it's not that storing information in the individual cells,
30:28 that you're creating these incredibly interesting networks have a specific pattern that they produce
30:35 the particular activity. That's what neuroplasticity , is the ability to do
30:40 And the truth is you can do your entire life. So even though
30:44 networks are being formed specifically in those times embryogenesis and primarily during that whole
30:51 of time during puberty, when your is completely remodeled. Do you remember
30:55 horrible that was? Do you guys that at all? How you're always
30:59 , always sad. Your emotions were in like two different places and you're
31:03 24 7, you know, I , it was like right around the
31:06 for you all maybe it was last . Yeah, I just don't even
31:12 respond. I've got two teenagers right that it's just, it's like a
31:17 household. One, one's happy one , the other one is mad and
31:20 they flip. It's like, do guys meet in the morning and talk
31:23 which one's gonna do? What All right. So this little slide
31:33 basically a summary of what I've kind says here, look, information is
31:35 to be coordinate and integrated because what going to be doing is we're going
31:39 create these complex patterns called neural You'll also hear the term neural
31:46 They're very, very similar. All . So these circuits are can be
31:50 or they can be distributed when we're about localized. That means the neurons
31:54 all collectively in one place and they're together if they're distributed, that means
31:58 they're going to be in different parts the central nervous system, but they're
32:01 talking to each other. All typically, when you're talking about a
32:05 circuit, it's gonna be restricted in number of inputs and the number of
32:09 destinations. In other words, you have one that goes in and you
32:13 like 10 neurons and then you'll have circuit that comes out. I'm
32:16 I'm just making up numbers. but the idea here is the internal
32:20 is less important. It's the input the output are gonna be much,
32:25 smaller than what's going on inside that . And then lastly, they can
32:28 simple or complex and this is what gonna look at. There's four basic
32:32 of circuits. If you take a , two class, you'll talk about
32:35 types of circuits when you talk about . All right. So, if
32:39 ever wondered why you have to take as a biology major, that's the
32:43 why you gotta learn about circuits and . All right. So let's take
32:48 look at these um simple circuit is , very simple. It's name,
32:53 are not particularly common, they're but this would be an example
32:56 So it's basically one cell talking to cell simple. That's simple.
33:02 Complex. All right, complex is there's gonna be multiple connections. Notice
33:06 this case, we still have just neurons but notice what we have is
33:10 created this neuron here talking back to neuron that's feeding back to it.
33:15 becomes a little bit more complex. . Right. So there's a feedback
33:19 that's taking place in this complex one we're talking about complex complex are kind
33:24 the rule simple is kind of the to the rule. And I've mentioned
33:30 are four different types of circuits. two are the easy circuits. All
33:35 , converging and diverging. All when things converge that means they come
33:39 . And so you can see here do we have, we're gonna converging
33:44 converging, we have three different They're all coming down on this one
33:48 . So, what we're doing is concentrating signals to single output. All
33:54 , that's what's going on here. right. They don't know where the
33:58 is coming from. They're just processing . All right. And uh these
34:03 very, very common. So, some examples that we have up here
34:07 . Um, think about what makes salivate. I mean, if you're
34:10 across campus and you smell barbecue that you hungry, make your mouth start
34:16 . I mean, even the vegans your mouth starts watering them. I
34:19 , it's, it's true because it's proteins in the smoke. You're like
34:23 your body says, oh, I that in my body and you're
34:25 no, no, I can't eat . I'm a vegan. Well,
34:29 I'll be a vegan. I'll eat today. Um Anyway. All
34:33 So that would be an example. you have, you can see things
34:36 make your mouth water. You can things when you put food in your
34:39 , that makes your mouth water, ? When you smell things. All
34:42 . So multiple senses are impacting the that cause the salad glands to
34:50 That would be an example of Oh even texture will make you salivate
34:55 you have really, really dry put chocolate in your mouth. All
34:58 , the texture of the chocolate plus sugar in the like the milk chocolate
35:01 make your mouth water. So if ever are like, you have to
35:07 a talk dry mouth, that, an easy one, diverging circuits.
35:11 we're doing is we're amplifying the So here what we're doing is we're
35:14 be taking a single signal and acting on multiple of the neurons are sending
35:19 to multiple different places. This is amplification. All right. Um So
35:25 of this would be uh neurons that walking. So for example, we
35:29 talked about walking. What is Walking is, have I not talked
35:33 ? I probably haven't talked about It's, it's again, two classes
35:36 guys are off a little bit, is not falling. Notice that,
35:42 ? What swimming? Well, if is not falling, swimming is not
35:49 , right. Right. So what walking? I basically take my
35:52 I mean, I'm out of balance , right? And you can't see
35:55 leg, my, my other leg actually doing a lot of this,
35:58 ? But if I take my foot , what I do to put my
36:00 forward and I catch myself, That's all I'm doing when I'm walking
36:04 lifting and shifting weight and catching myself I fall. And so what in
36:10 for that to happen is not just lifting my foot down. It's actually
36:14 many, many muscles other than the muscles that are involved in changing my
36:19 and keeping myself upright. And so all is through divergence. Basically,
36:23 like when you walk, let's send signal all these different muscles and tell
36:26 those different muscles what to do. would be the example. All
36:32 then we get to the weird All right. So this is a
36:35 generating circuit. Um And we have parallel after discharge, the rhythm generating
36:40 is a positive feedback loop. All . So in the little model you
36:46 here, we have three neurons. this neuron fires, it's gonna stimulate
36:51 cell which is gonna go there. notice this cell feedback feeds back and
36:55 to this one. So what we're is we're getting a feedback loop in
36:58 direction. But this neuron also branches feeds to this one which sends a
37:03 to keep this going. So what is you end up creating a
37:08 All right, I'll give you an of this is your breathing. All
37:12 , when you breathe, you start a small muscle contraction that leads to
37:17 larger one which leads to a larger and so on and so on and
37:20 on. This is what causes your to go and then something external to
37:25 system says stop. And so that the muscle to stop and then the
37:29 relaxes again and then the neuron starts then he builds up, builds
37:33 builds up and creates a larger feedback . So that you can breathe in
37:37 . So it's breathe in, relax muscle, breathe in. And it's
37:43 the neurons involved create a larger and response through a feedback loop like the
37:49 one. All right. That would an exa a simple example, the
37:53 wake cycle is also one that's uh , but it's a little bit harder
37:57 explain. But if you think about out to you parallel after discharge,
38:02 we're trying to do is we're trying create a very large output. All
38:07 . Now, this picture is not , but I want you to look
38:10 the length of the neurons. So one is shorter than that one.
38:14 you agree with that kind of, ? This one is uh is shorter
38:18 this one, but it has And so remember we talked about synaptic
38:22 , right? Do you remember synaptic ? No, you don't remember
38:28 That's what your brain's doing right As you try to think about what
38:31 glaze, it's like it's basically the of time it takes one cell to
38:36 to release the neurotransmitter and get the cell to fire very, very small
38:39 of time. It's a small delay causes the the signal to kind of
38:44 down. All right. So in , our target cell is the
38:50 All right. So you can I have my three branches. So
38:53 first signal is going to go boom hit that one. And so let's
38:57 presume each of these results in an potential. So if this one comes
39:01 and causes this one to create an potential, that's your first signal.
39:05 branches are roughly the same length This one's shorter than that one.
39:09 this cell, all three of there would be a synaptic delay.
39:13 the signal arriving here is going to a little bit later than the one
39:17 there. And then it goes through one and causes this cell to
39:20 So it'd be like this one's number . That would be number two,
39:23 would be number three and this one two neurons. So it would have
39:27 longer delay. So this one would number four. And so this cell
39:31 here is going to be stimulated like 1234, right? So that receiving
39:38 has a larger response. Basically, sending a signal like this just the
39:43 . All right. So you're getting extended pattern in that receiving cell.
39:50 kind of makes sense. So I'm crickets, actually, I'm hearing the
39:58 of the lights. But and if start listening, now you perceive
40:03 the humming of the lights. Does kind of make sense? So the
40:08 of like instead of they were just one cell keep telling me to
40:11 It's like one signal is all you . And then the responding cell goes
40:15 ba, ba, ba ba like . All right. So notice here
40:22 takes one stimulation here to get 1234 to fire. This is the receiving
40:31 . So it's 123 and then this over here. So it'd be one
40:35 , two, cell, three, , four cell. So one signal
40:38 in four responses in that last c that latter cell. So it becomes
40:43 much bigger response. All right. we get these complex inputs. All
40:51 , your phones, your circuit boards your computers do things like this,
40:57 ? It's creating these unique signals. is kind of how those things
41:06 All right, you can imagine all networks having all these really weird
41:15 And so it's these patterns of these that allows your brain to store information
41:23 the patterns that it creates through these of weird networks. This is how
41:28 order thinking is. What's higher order ? You walk by a garbage.
41:36 you see it? Cake sitting on plate? No bite in it.
41:41 order thinking is I'm hungry. Do take the cake? Do I not
41:46 the cake? Right. Making processing information based upon what you
41:55 and don't know. All right, decisions. Do I cross the street
42:00 that bus coming at me? All . Oh, look, there's a
42:05 bill on the ground. Is it ? High order. Thank you.
42:14 these networks, these circuits are gonna , like we said, way back
42:20 you first begin developing, but they're complete. All right, they're gonna
42:26 maintained by the use and they're gonna that plasticity. So, have you
42:32 seen, I mean, again, babies are interesting. Right. They're
42:38 by everything and they put everything in mouth. Why do they put everything
42:41 their mouth? Do you think it's just, it's just a phase?
42:46 , it's not just that they think it's food, it's, they're exploring
42:49 environment by tasting it. That's the thing that they can do.
42:55 So, if you hand them they're like, and then they grab
42:58 and what's the first thing they You know, you're like something
43:03 I gotta wash and new and new are always freaking. Oh no,
43:07 putting it in their mouth. Yeah, they've got immune systems,
43:09 worry about it. That's, that's they do. Just as long as
43:12 not cat poop, you're probably in shape. Cat poop has a lot
43:17 stuff that's bad in it if you want it. I'm not just talking
43:19 it as cat poop. It's, crazy cat lady syndrome. Um
43:25 so you, you, these networks gonna display plasticity and so what you're
43:31 is every time you do anything you're and rebuilding these networks. All
43:37 So that's why I was mentioning the you do something practice makes perfect.
43:42 not just athletics. It's not just , right? It's not artwork,
43:46 everything that you do. You make by cr by doing that pattern over
43:52 over again because what you're doing is solidifying and strengthening the neural network that
43:57 creating. Right? I think I you, my son just started
44:02 I think I told you that at beginning of the semester because it was
44:06 me terribly frustrated because it was like old enough. You should have your
44:10 but, but mom will drive me school. Yeah, your mom doesn't
44:13 to drive you to school and I'm doing it so get your license.
44:16 , um, you know, we four kids. I mean, we
44:20 plenty of people to drive around the , you know, and no one's
44:23 us to do it. I we should just put Uber on the
44:25 of the car and say just come , that's what rideshare is. Come
44:29 . All right. But you he was scared to drive because he
44:35 used to it. And think about you first started driving, you got
44:37 that car, you got your license the first time. You got your
44:41 hours behind the wheel, right? were you ready to get on Houston
44:46 ? Uh uh, now how about are you a road warrior?
44:51 You know some of you are uh uh cause you're not doing it
44:54 , you gotta get out there and know, fight the traffic, get
44:57 front of us fast. People like , you know, extend that left
45:03 with a finger, don't do You'll get it shut off.
45:08 but the idea is, is that become better at driving in Houston traffic
45:13 driving in Houston traffic, right? get, become a better swimmer.
45:18 you go and swim, you become better basketball player. When you go
45:22 shoot baskets, you get better at when you do tackling drills and you
45:29 better at a and if you do MP homework and studying. All
45:35 And then you're like what? I how I did that. I
45:39 I brought it all the way back . Yeah. No, but it's
45:42 . It, it doesn't matter what is. All right, you wanna
45:45 better at a video game, pick game, you know, you wanna
45:50 better at it. How do you better at it? You play it
45:53 the time? So that's it. right. Practice. Make perks that
45:57 established in the networks. These networks be modified all the way until you
46:04 no longer part of this world. right, the lie is you can't
46:09 an old dog new tricks. That an absolute lie. You want,
46:13 wanna see something interesting. We gave great, my grandmother who's 96 years
46:17 her hands, she likes to, likes to read a lot. All
46:21 . And so she's obviously old school so she'd hold a book and then
46:26 have a magnifying glass and it was like this nightmare because, you
46:29 she has horribly arthritic hands at this . She stopped driving when she was
46:35 . I know. It's crazy. . Oh, I, I can
46:38 you this. This is a, is a, a warrior of a
46:41 . She broke her hip like when was 90 years old because she was
46:45 ice off her patio. I was sweeping it. She fit and then
46:50 like, no, no, it's no problem. I'll,
46:52 I'm fine. It took her like week before she said, OK,
46:54 me to the hospital anyway. Um I'm this old dog, new
47:00 They got her an ipad. Why they get her an ipad? So
47:03 could read her books. She didn't to flip pages. She didn't have
47:06 carry a microphone m uh a magnifying . She now has print that's like
47:10 big and she like has six words a page and she can go like
47:14 , you know, new trick, ? It takes a while to
47:22 Oh, I don't flip a right? But once you figure it
47:27 , it's easy mode. All Now, one of the things that
47:30 see is we can create these complex which we've been describing. But the
47:35 thing that it does, it allows to produce reflexes. You see how
47:39 doing all these weird trans, a transitions here. OK. So let's
47:43 into reflexes. What's a legs? right. This is the definition.
47:48 rapid preprogrammed and involuntary. All So those are the characteristics. So
47:54 gonna be a muscle gland to some of stimulus. So it's rapid preprogrammed
48:02 it's involuntary. Should we have fun it? You want to have fun
48:07 it? All right. You wanna up, we're gonna have fun.
48:12 like, damn it, I never this in class. But why not
48:20 on the table? All right. the way back in a crush.
48:26 , you, you don't even need crush. You can just sit like
48:27 . All right. So I'm gonna you. I'm not gonna hit you
48:29 . Watch this. All right. I'm just gonna hit this. All
48:33 . I gotta find it. It's easier with the hammer. I
48:43 have a hand. OK? Never me. Try to resist me.
48:58 , it's just, it's always gonna it. I'm, I'm not hitting
49:00 hard. That's why you can do to yourself. I mean, it's
49:03 few things. Yeah, he's a sport. Yeah. Yeah, I
49:09 give him an, a just for up here every single time I call
49:11 up here. You're like, you're , man, he's like, maybe
49:19 else do you need me to Uh, but all Right. So
49:22 preprogrammed. All right. So the here is that it happens every
49:27 Now I notice every time I hit on the knee it didn't happen.
49:29 that was because I wasn't hitting the spot. All right. And trying
49:33 find the right spot sometimes takes a bit of work. And that's why
49:35 have the little tiny, little hammer on the knee. So that's just
49:39 example of one here, right? the knee jerk reflex. All
49:42 So let's just kind of look at of these words, what are the
49:45 ? It is simply a sensory input initiates the reflex. So when you
49:48 your stimulus, that's what it If I take a flashlight, fla
49:51 in your eye, that's a All right, it's rapid. Meaning
49:56 are very few neurons going to be . There's no synaptic delay. You
49:59 have to think about it. The are just in a chain. It's
50:03 input, process output. We'll see in just a moment. All
50:07 Pre programmed. Every time you do it's going to get the same
50:11 All right. So this is what showing you here is going to be
50:14 suckling response. All right. So you have again, a, a
50:19 child or a newborn and you tickle here, what they're gonna do is
50:23 gonna turn their head seeking a nipple that's what they think that is if
50:27 have something brushing their face, they it's time to suckle. So
50:32 you know, do that. That's they're, they're trying to show
50:35 All right. There's a Babinski You can go across the bottom of
50:38 foot and as the foot do this weird curl. All right. It's
50:45 . It means you cannot think about . You don't need to think about
50:47 . It can't be suppressed. There's you can do to avoid it.
50:50 just happens. All right. And that's what a reflex is. So
50:56 , we think about the reflexes being cord and that's kind of where we're
51:00 . But there are other types of beyond spinal cord reflexes. It's just
51:04 easiest one to deal with. All . And so here, the spinal
51:08 , when we're talking about the spinal is involved in the reflex. It
51:11 where the information is processed. It part of the central nervous system.
51:14 processes information. It doesn't need to up to the brain. So your
51:17 cord bo is doing the work that brain does. It's just very simple
51:24 . All right. So basic reflex the things that you're seeing right
51:28 These are unlearned. They're built in , the baby's smiling, you
51:32 you kick in your knee, the babinski reflex, the the suckling
51:37 These are all things that are in in humans at the time of
51:43 All right. And we have condition . You, you're familiar with Pavlov
51:48 Pavlov's dog? You've heard of Right. Pavlov had a dog.
51:52 rang the bell. He fed the , rang, the bell,
51:54 the dog rang the bell fed the rang, the bell, didn't feed
51:56 dog. What the dog do he . Pavel. No, he's,
52:00 salivated. Right. But that's the . And see we're all conditioned,
52:06 ? We go through life and we these patterns and so the patterns condition
52:12 to respond. So like when you a yellow light, what do you
52:16 ? This is the best response. down. People are speed up.
52:20 , it depends on who you right? And, and where you're
52:23 , Houston, we speed up, ? It's like, can I make
52:27 light? It turned yellow three seconds , I think I got it
52:32 But I mean, here's an easy . I mean, in high school
52:36 bell goes off, what do you ? Get up and go? I
52:39 , it's just like I, I'm robot, I will hear the bell
52:42 I will do what the bell tells to do. All right. That's
52:44 conditioned response. All right. These examples of conditions. So these are
52:51 after practice and learning. We go motions and when we think go through
52:55 motions, athletes, when you, you go and start your regimen,
53:00 ? Whether it be, you uh you know, when you go
53:03 start stretching and stuff like that. go through these actions. This is
53:06 conditioned response. It's like I know I go and do this, these
53:10 the steps I go through. We're the only creatures that do this.
53:14 creatures do this. I'm just gonna you the example I can think
53:16 Off the top of my head was . Racehorses have a regimen. If
53:20 , if you muck with that, can guarantee that that racehorse is gonna
53:24 because basketball players, you know, teach them when they're shooting the free
53:28 , create your rhythm, right? they say something like that, do
53:31 rhythm. And so what they do once you create a pattern, you
53:34 with that and you reinforce it, it. It's a conditioned reflex.
53:37 don't even think they just go to line. All those people waving uh
53:41 heads and doing the uh the sticks stuff like that aren't gonna do anything
53:45 them because they've created a pattern. right. So that's condition reflex.
53:49 picture right here is one of the important ones that you'll see in this
53:54 . All right. Now, why important is not because everything on here
53:58 important. It's just you'll see this at least three times in different
54:03 And it kind of gives you a understanding of all the things you need
54:06 know in the central nervous system and peripheral nerve and their relationship to want
54:10 know. All right. So what have here is the basic reflex
54:16 All right. So you know, basic reflex arc you're like good to
54:19 when it comes to reflexes. All . The first thing we need is
54:22 need to have some sort of So in this particular case, we
54:26 a nail, I always say it's electric nail because of lightning bolts,
54:29 whatever it's pain, right, we a nail that comes in. So
54:32 have the receptor to detect that that receptor is uh produces a signal
54:40 then travels up an Afer pathway. is into the central nervous system.
54:48 right, that a fair pathway goes the central nervous system and then terminates
54:53 a processing center or an integration So in this particular model, our
54:58 center is a single neuron. What refer to as an interneuron, interneurons
55:04 are a word we use to say in between other neurons. OK.
55:09 when you see that, just oh it's a processor. All
55:12 And so what this is looking for interneuron is saying, hey, when
55:16 receive a signal, I send a . And so it's gonna process that
55:21 . Oh I received the signal. I'm gonna send a signal that signal
55:25 out via an E ferr pathway. it goes to the thing that is
55:30 to respond to the stimulus what we to as the effector, it causes
55:34 effect. So, receptor a fent eer effector know those five things,
55:43 them, tattoo them to your All right. Not in the
55:48 you know, with the ink because cheating but you know good ink.
55:57 . OK. Receptor A fair pathway center eer pathway. Now I'm gonna
56:04 there for a second. The proper for those is er and efferent but
56:08 is Texas. So we say a and E fern to accentuate the A
56:14 the E to know which one's going and which one's going out? All
56:18 . So, afferent or a fern E fern is the out. And
56:24 the last thing is the effector causes effect. So in this particular
56:30 I step on a tack, I the muscle to lift the foot up
56:34 move it away from the tack. . And that's all done at the
56:39 of the spinal cord. Now, are different types of reflex pathways.
56:48 right, without looking at all the up there, what do you think
56:51 means? 11, what one So in this particular case, what
56:56 have here, this is that stretch , right? What we have is
57:00 , there's our, our receptor, detecting the stretch in the tendon,
57:05 causes the signal to go up. is no interneuron, it has just
57:08 single synapse that tells the motor neuron contract the muscle. That's all it
57:14 . So, very, very That would be an example of a
57:17 . Polysynaptic means more than one. it's poly means many. And so
57:23 that would be the example of the that we just saw over there.
57:28 right. So there's an interno 12 in this case. Have you ever
57:33 yourself on a Bunsen burner? Don't that if you do that. I
57:36 , just, just if something is , don't touch it. OK.
57:42 what this is showing. Poly snapped . Now, there are different types
57:47 reflexes. All right, there are we refer to as somatic reflexes and
57:52 that are referred to as autonomic somatic soma body. So when we're
57:58 about somatic reflexes, we're talking about that deal with our muscles. All
58:02 . Things that we would normally be to control skeletal. All right.
58:08 that would be somatic over here. going to the surface of the skin
58:13 would be somatic. All right, . On the other hand, do
58:17 confuse with automatic, automatic means it happen automatically. All right. But
58:24 here, what we're doing is we're to systems that we do not control
58:29 , in a, in a conscious . All right, we're talking about
58:33 like your guts, your viscera. the organs are autonomic. All
58:39 So we're gonna talk like I the very last thing we talk about
58:43 this whole semester is the autonomic nervous and it refers to the things that
58:48 not under conscious control but are under control. And I'm not talking like
58:54 cause can you close your eyes? you, can you let me
58:57 Close your eyes, open your close your eyes. There we
59:01 open your eyes. All right. . All right. So,
59:04 but that's skeletal muscle but it blinks its own, right? I
59:08 you, you don't have to think yourself. Blink, blink,
59:11 you don't do that, right? there are things that can be
59:15 which are still somatic, right? breathing. It's another one. Do
59:20 have to think about breathing, breathe , breathe in, you know.
59:24 , that's automatic because it's under, under a regulatory system that allows that
59:31 happen. But it's still somatic because can hold your breath. I can
59:35 myself breathe fast, see, whatever. All right. But I
59:43 tell my digestive system to digest. can't move things through that.
59:49 I can't tell my heart to All right. Speed up,
59:52 slow down heart, right? You do that. That would be
60:01 All right. Last little bit here we're gonna deal with the spinal cord
60:05 its anatomy. So, what we've now is we've kind of talked about
60:09 networks that are gonna be representative of going on in these systems that we're
60:15 at. All right. And so starting point is the most primitive form
60:20 the central nervous system. It's a . And so it is the structure
60:24 exi exits from the base of the . It's continuous with the brain
60:29 It is enclosed by a bone. you remember we talked about the
60:33 So there is the spinal cord, is the body of the vertebrae that
60:37 the vertebral arch right there and see protected by that, you get a
60:41 bunch of vertebrae stack, then you the bony tube that is flexible,
60:45 allows it to sit in there. like the brain. We saw uh
60:50 we talked about cerebrospinal fluid, we about this structure that surrounds. So
60:54 are the meninges that surround it. right. And then the cerebrospinal fluid
60:59 in that subarachnoid space surrounding the Now, this is not an easy
61:04 to see here because the cartoon is tiny. But that's what all these
61:08 can see the little that would be meninges right there on that edge.
61:13 right. Now, along its it is subdivided um based on the
61:19 the structures of the spinal cord, ? So we had these four
61:23 So we had the cervical region, thoracic lumbar and sacral. And then
61:27 don't really have a coccidial region, it would be like that would be
61:31 the portion that extends outward. And what we do is we say where
61:36 see the spinal nerves exiting from those . That is the name of that
61:41 , the spinal cord. So we the coccidial would be coming right down
61:47 to the very tip. Now, first thing we're gonna talk about when
61:52 come back is we're gonna talk about spinal nerves. So we're gonna leave
61:56 spinal nerves behind for a moment. just focusing here on the central nervous
62:01 are nerves found in the central nervous . Thank you. I just want
62:06 see if you guys are paying No, they're not. So when
62:09 get to the nerves, you're now peripheral nervous system. All right.
62:13 structurally, you can see it is flat on the two edges.
62:17 it has a uh the the posterior or dorsal side, the ventral or
62:22 side. Uh there's two grooves. we refer to the dorsal side as
62:26 uh dorsal, medial sulcus. This be the ventral, medial or
62:30 medial uh uh uh medial fissure. ? One's a fis fissure? One's
62:35 sulcus? I don't know just it all right, depending on where you're
62:41 . It's not all going to look pretty in one place. It actually
62:44 shape slightly depending upon where you We mentioned this already that the gray
62:49 is centrally located. The white matter located uh on the external portion or
62:54 cortical portions here. All right, is the central canal. Now,
63:00 we're looking at here is a structure is extending out and into the
63:05 All right. So, um let see that I actually named those.
63:09 did not name the gray matter. gonna come back and name parts of
63:12 gray matter. All right. So the white matter is located, we
63:16 them a special name, we call funiculi. All right, because they're
63:23 , funiculi fun just work with All right. So the one on
63:28 posterior side is gonna be referred to the posterior funiculi. The one that's
63:35 on the sides would be the lateral . And then the ones that are
63:41 are gonna be referred to as the ventral funiculi. So see nomenclature is
63:47 particularly difficult. Now, the one that's interesting is that while these
63:52 so like, you know, you the spinal cord left and right.
63:56 so what you'd say is OK, dorsal funiculi uh on the left is
64:03 connected to the one that's on the . But when you get to the
64:07 ventral side, those two sides are . In other words, the fissure
64:11 work all the way down. There's a little tiny uh crossover, all
64:17 . That's called uh a cage. right. So we have this measure
64:23 white chami that allows for the two to be connected. Now, what
64:28 seeing as I said, this is in and out these are tracks,
64:32 right. So these are axons that traveling back and forth in and out
64:37 the screen at you. All So the ones that are going up
64:41 the brain stem and to the those would be ascending, the ones
64:45 are coming down from the brain and brain stem would be descending tracks.
64:52 . So the other way that you look at these is you can think
64:55 ascending tracks as carrying a fern right? Or sensory information, descending
65:03 are the same thing as e So, information is coming outward.
65:08 so that is gonna be motor So those three words are synonymous.
65:13 a fern sensory, got those three then motor descending and E ference,
65:22 three go together. All right, combine, you use those three
65:27 in unison. Now, all a is, is just a bundle of
65:32 moving in the same direction. So like highway 59. If you get
65:37 highway 59 which way are you If you're going south, where are
65:41 going towards Sugarland? If that I'll go with Sugarland. All
65:47 I was hoping you'd say Victoria, we'll stick with that. All
65:51 So that's what we're doing is we're bundle the tracks traveling to and from
65:56 same location. All right, there eventually be branching further outside. But
66:01 when we're getting in the nerves, we're coming to the central nervous
66:04 we're basically bundling things together that are in the same direction to the same
66:09 . Gray matter is a little bit complicated. Well, not really,
66:13 call the gray matter horns. All . So we're using a different picture
66:16 . You can see that the gray kind of has this weird butterfly shape
66:19 it all around. It is the matter, those funicula. So here's
66:25 funicula again. So that would be , lateral, ventral and then up
66:30 that butterfly shape you can see we've coded it and those represent the different
66:37 . All right. So we have dorsal horn, we have a ventral
66:42 and this is a little hard because butterfly but it's easier if you look
66:46 here, that would be the lateral . So this one that's been kind
66:49 color colored yellow would be lateral. we don't name things just cause I
66:56 we do sometimes but there's a reason things are distinguished from each other because
67:02 neuron cell bodies are located in these areas. All right. So remember
67:09 we said, white matter represents And so we have the ascending and
67:13 tracks and the gray matter represents where bodies are located of neurons. So
67:19 cell bodies do we find where? right. Well, in the dorsal
67:24 , we got fibers coming in from outside. Those would be sensory fibers
67:28 they're terminating on interneurons in the lateral . So what we have here in
67:34 lateral in the dorsal horn are the body of interneurons receiving sensory information.
67:42 cell bodies of sensory neurons are not in the central nervous system. They're
67:48 outside over here in the peripheral nervous . In that big giant ganglia,
67:55 called the dorsal root ganglia. We'll with that on Thursday. All
68:00 in the lateral horn, which is yellow here. That is the location
68:05 the cell bodies of motor neurons belonging the autonomic nervous system. All
68:12 So that would be going to your and then the ventral horn, the
68:17 that's coated red here represents the cell of motor neurons that are going to
68:24 somatic system. All right. So muscles, so easy way to remember
68:30 dorsal horn, inter neuron cell lateral horn, motor neurons, autonomic
68:37 motor neurons, somatic. So And where are the sensory cell bodies
68:46 ? We're not worried about them. , the meninges are continuous. So
68:56 can create those same things. They're still there. There's a slight
69:00 The dura matter is not as thick what you saw in the, in
69:03 cranium. It is basically a single instead of two layers. Um it
69:08 between the vertebrae and keeps going down the length of the spinal cord.
69:14 it just wraps around the spinal nerves they travel down through that uh vertebral
69:18 uh column. There is a small . So here, right here between
69:24 dura and the bone that's filled with , that's the epidural layer, uh
69:28 epidural space that fat's there to serve kind of padding or protection. Uh
69:33 sub uh the CS F is still be in the subarachnoid space. So
69:36 be dura arachnoid, subarachnoid space. A is closely adhered to the spinal
69:43 just like we saw with the All right. Oh You can't barely
69:50 them. So right there and right . Do you see that little little
69:55 difference that's called the denticle ligament. vic ligament basically holds the spinal cord
70:02 place so that when you move around spinal cord doesn't just kind of get
70:07 . It just kind of holds it place. This is my last
70:12 Yes, it is. And we're of here. All right. Last
70:15 bit. So when you began your spinal cord and your vertebrae were
70:22 same length, but then you quickly and then your vertebrae grew faster than
70:27 spinal cord. All right. So now, your spinal cord is significantly
70:33 than your vertebrae. It ends uh around T or was it L one
70:38 two? Rough? Yeah, L L two right around there. So
70:42 you can see is here spinal cord then all of a sudden it tapers
70:46 and comes to a point and that off is what is referred to as
70:50 Conus meis. So that's around L L two. But you still see
70:55 have fibers and there's still dura matter those fibers are gonna continue down and
71:00 out as those spinal nerves to the to which they're supposed to go.
71:04 right. So those spinal nerves remain to hold the spinal cord attached to
71:10 bottom of the uh vertebral column. is a little tiny uh cord called
71:16 Pelli terminale. This again prevents the from be getting joust around and bouncing
71:22 over the place. A whole bundle spinal nerves looks like a horse's
71:29 So we call it the horse's the kata ana ka really but qui
71:38 course. All right. And then mentioned this, we said that there
71:43 spinal nerves. And so if you out this uh vertebrae, there's 31
71:47 are 31 pairs of spinal nerves exiting between each of the end of the
71:52 , the place where the exit is the vertebrae. So the introvert
71:56 So it's collectively the foramina. And finally, there are two enlargements.
72:01 an enlargement up here and then there's enlargement down in here. These are
72:07 to collectively as a cervical enlargement or lumbosacral enlargement. And these represent the
72:13 of fibers that are exiting out to innervate the upper and the lower
72:19 All right. So, in those spots, you'll see the spinal cord
72:23 kind of this widening and then gets down to shape and then it widens
72:27 before it, uh uh divides off becomes nothing. All right. So
72:36 a lot today. When we come , we're going to jump in the
72:39 nervous system and we're going to deal nerves. We won't be calling you
72:43 to do stuff. Yes, Uh huh. This one says it
72:51 the can to
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