1 00:00:00,250 --> 00:00:01,800 The following content is provided 2 00:00:01,800 --> 00:00:04,040 under a Creative Commons license. 3 00:00:04,040 --> 00:00:06,890 Your support will help MIT OpenCourseWare continue 4 00:00:06,890 --> 00:00:10,740 to offer high-quality educational resources for free. 5 00:00:10,740 --> 00:00:13,360 To make a donation or view additional materials 6 00:00:13,360 --> 00:00:17,241 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,241 --> 00:00:17,866 at ocw.mit.edu. 8 00:00:23,950 --> 00:00:26,490 PROFESSOR: This is 914, and the people in the back 9 00:00:26,490 --> 00:00:29,340 may sometimes have trouble hearing me. 10 00:00:29,340 --> 00:00:32,740 So you should always get-- maybe we should actually 11 00:00:32,740 --> 00:00:37,940 change tables in the future, so you can all sit closer. 12 00:00:37,940 --> 00:00:40,300 I don't have a real loud voice. 13 00:00:40,300 --> 00:00:43,570 I can ask them for an amplifier, but in a small class, 14 00:00:43,570 --> 00:00:46,698 that's sort of awkward. 15 00:00:46,698 --> 00:00:49,594 AUDIENCE: [INAUDIBLE]? 16 00:00:49,594 --> 00:00:51,510 PROFESSOR: Yeah, well, if you stop hearing me, 17 00:00:51,510 --> 00:00:53,710 just come closer. 18 00:00:58,160 --> 00:01:00,022 There's one there. 19 00:01:00,022 --> 00:01:02,055 And there's a few there that are closer. 20 00:01:08,960 --> 00:01:12,340 So this is the plan. 21 00:01:12,340 --> 00:01:15,400 I want you to acquire, and by acquire 22 00:01:15,400 --> 00:01:18,440 I mean in here in your mind, I want 23 00:01:18,440 --> 00:01:22,980 you to have an outline of vertebrate neuroanatomy, 24 00:01:22,980 --> 00:01:24,320 especially for mammals. 25 00:01:24,320 --> 00:01:26,790 But we'll learn enough about non-mammals 26 00:01:26,790 --> 00:01:31,080 that you'll have some understanding of them, too. 27 00:01:31,080 --> 00:01:36,790 And neuroanatomy anatomy is not exactly an exciting topic. 28 00:01:36,790 --> 00:01:38,900 It's usually boring. 29 00:01:38,900 --> 00:01:46,400 But it doesn't stay that way if you know why it's like that 30 00:01:46,400 --> 00:01:48,000 and what it does. 31 00:01:48,000 --> 00:01:51,310 So that's why, and when I wrote the book that's 32 00:01:51,310 --> 00:01:58,160 the text for the class, I try to explain where this came from, 33 00:01:58,160 --> 00:02:01,296 how it develops, how it evolved. 34 00:02:01,296 --> 00:02:04,970 And for evolution, yes, I can use molecular data, 35 00:02:04,970 --> 00:02:08,600 but that's only in conjunction with comparative anatomy, 36 00:02:08,600 --> 00:02:14,030 look at a broad range of species, some of which 37 00:02:14,030 --> 00:02:14,920 are very primitive. 38 00:02:14,920 --> 00:02:19,520 That is, fossil record can trace them way, way back, 39 00:02:19,520 --> 00:02:21,005 like the sea lamprey, for example. 40 00:02:24,991 --> 00:02:27,240 And as far as if you're going to talk about evolution, 41 00:02:27,240 --> 00:02:28,820 you've got to talk about function, 42 00:02:28,820 --> 00:02:36,480 because things don't evolve-- they evolve mainly 43 00:02:36,480 --> 00:02:41,015 to serve adaptive function, that is, by natural selection. 44 00:02:41,015 --> 00:02:45,070 And I'm assuming that, and I'm a Darwinian in that sense, 45 00:02:45,070 --> 00:02:48,330 and I recognize there are other mechanisms of evolution that 46 00:02:48,330 --> 00:02:53,810 result in change, but I believe the major things, especially 47 00:02:53,810 --> 00:02:59,300 for things like the CNS, which controls function, 48 00:02:59,300 --> 00:03:07,270 is due to selective survival of species. 49 00:03:07,270 --> 00:03:10,690 So today, we'll start out with a little terminology. 50 00:03:10,690 --> 00:03:13,030 And then we're going to talk about cells. 51 00:03:13,030 --> 00:03:17,030 And the next time we'll be talking about the way 52 00:03:17,030 --> 00:03:18,520 some of the cellular mechanisms are 53 00:03:18,520 --> 00:03:22,450 used to study pathways, connections. 54 00:03:22,450 --> 00:03:26,850 And we'll hear a little bit about that today. 55 00:03:26,850 --> 00:03:30,080 You should be getting familiar with the Stellar site. 56 00:03:30,080 --> 00:03:39,990 And you go to the-- you log in, you go to this Materials 57 00:03:39,990 --> 00:03:42,560 section, and you'll see at the top 58 00:03:42,560 --> 00:03:46,640 the General section and a Resources section. 59 00:03:46,640 --> 00:03:48,420 You'll find there a book list. 60 00:03:48,420 --> 00:03:54,540 Now, this year, I'm really only requiring 61 00:03:54,540 --> 00:03:58,980 as essential reading of my book, but there 62 00:03:58,980 --> 00:04:02,350 are some very interesting other books. 63 00:04:02,350 --> 00:04:04,135 And I post some of those readings 64 00:04:04,135 --> 00:04:08,320 as supplementary readings, and some of them are very helpful. 65 00:04:08,320 --> 00:04:11,186 If you get through with the reading 66 00:04:11,186 --> 00:04:15,970 and you haven't put your nine hours a week in yet, 67 00:04:15,970 --> 00:04:18,130 do some of the supplementary readings. 68 00:04:18,130 --> 00:04:21,010 The Allman book is a particularly interesting one. 69 00:04:21,010 --> 00:04:22,035 It's out of print. 70 00:04:22,035 --> 00:04:24,910 That was the problem with Freeman Press and Scientific 71 00:04:24,910 --> 00:04:26,375 American; books. 72 00:04:26,375 --> 00:04:28,700 They didn't keep books in print. 73 00:04:28,700 --> 00:04:31,980 Other publishers could pick them up, 74 00:04:31,980 --> 00:04:34,255 but so far, Allman hasn't been republished. 75 00:04:34,255 --> 00:04:36,640 And that's true also for [INAUDIBLE] and [INAUDIBLE] 76 00:04:36,640 --> 00:04:38,000 book. 77 00:04:38,000 --> 00:04:40,014 [INAUDIBLE] was my teacher in neuroanatomy, 78 00:04:40,014 --> 00:04:41,430 and he was a great neuroanatomist, 79 00:04:41,430 --> 00:04:44,530 and wrote a very interesting book 80 00:04:44,530 --> 00:04:46,650 that's still a good resource. 81 00:04:46,650 --> 00:04:49,180 So I will be posting those, too. 82 00:04:49,180 --> 00:04:55,750 I'm not posting the Larry Swanson's book Brain 83 00:04:55,750 --> 00:04:58,090 Architecture. 84 00:04:58,090 --> 00:05:01,670 It's a book with similar goals to my book, 85 00:05:01,670 --> 00:05:04,380 but it's a very different book. 86 00:05:04,380 --> 00:05:10,000 It doesn't have the general kind of coverage that I have, 87 00:05:10,000 --> 00:05:12,400 but it's very unique in many things. 88 00:05:12,400 --> 00:05:17,620 And I did make use of that book in writing mine. 89 00:05:17,620 --> 00:05:20,760 So some people might want to pick that up. 90 00:05:20,760 --> 00:05:23,310 And I always list where the relevant things 91 00:05:23,310 --> 00:05:26,850 are in that book. 92 00:05:26,850 --> 00:05:29,395 You have a copy in the reserve room, I think. 93 00:05:29,395 --> 00:05:31,340 AUDIENCE: Well, I have a personal copy. 94 00:05:31,340 --> 00:05:33,430 PROFESSOR: OK, well, we should check. 95 00:05:33,430 --> 00:05:36,570 Well, check the reserve room and find out 96 00:05:36,570 --> 00:05:39,850 to make sure that they put the library's copy on reserve. 97 00:05:39,850 --> 00:05:42,180 So in case you have time and want to read some of that. 98 00:05:42,180 --> 00:05:44,090 That's fine. 99 00:05:44,090 --> 00:05:48,300 Now glossaries are important because you will soon find out 100 00:05:48,300 --> 00:05:51,510 there's a lot of terms in neuroanatomy. 101 00:05:51,510 --> 00:05:53,150 And they come from the Greek. 102 00:05:53,150 --> 00:05:57,160 They come from the Latin, or various combinations. 103 00:05:57,160 --> 00:06:01,170 And there's a lot of structures. 104 00:06:01,170 --> 00:06:05,910 A lot more than we have time to mention. 105 00:06:05,910 --> 00:06:10,910 I doubt if I will mention the bundle of Vicq d'azyr. 106 00:06:10,910 --> 00:06:13,060 I might mention habenulointerpeduncular tract. 107 00:06:16,030 --> 00:06:17,760 These are just, they're synonyms. 108 00:06:17,760 --> 00:06:20,180 They mean the very same thing. 109 00:06:20,180 --> 00:06:22,400 The second way, that's easy. 110 00:06:22,400 --> 00:06:23,922 If you know what the habenula is, 111 00:06:23,922 --> 00:06:25,630 you know what the interpeduncular nucleus 112 00:06:25,630 --> 00:06:28,270 is because it's the habenulointerpeduncular tract. 113 00:06:28,270 --> 00:06:30,480 It goes from one to the other. 114 00:06:30,480 --> 00:06:32,140 And a lot of tracts, fortunately, 115 00:06:32,140 --> 00:06:35,880 are named that way, but not all. 116 00:06:35,880 --> 00:06:38,250 And there's a lot of synonyms. 117 00:06:38,250 --> 00:06:40,800 You will see some of that right away. 118 00:06:40,800 --> 00:06:43,570 So you just get used to it, a little suffering, 119 00:06:43,570 --> 00:06:45,790 especially earlier in the class. 120 00:06:45,790 --> 00:06:50,160 And it might make you feel a little lost once in awhile. 121 00:06:50,160 --> 00:06:54,410 But be patient with yourself, and just put the time in. 122 00:06:54,410 --> 00:06:57,220 And I will go over things. 123 00:06:57,220 --> 00:07:01,600 The more important things I will return to a number of times 124 00:07:01,600 --> 00:07:03,750 to make it easier for you. 125 00:07:03,750 --> 00:07:07,710 I use the method in the book, and we'll use it in the class, 126 00:07:07,710 --> 00:07:12,735 because I'm basically-- the book originated from this class, 127 00:07:12,735 --> 00:07:15,520 from teaching here at MIT from a number of years. 128 00:07:20,540 --> 00:07:23,990 I'm posting not only the readings for each class, 129 00:07:23,990 --> 00:07:27,470 but I'm posting questions on the readings. 130 00:07:27,470 --> 00:07:32,500 I want you to read before the class. 131 00:07:32,500 --> 00:07:36,170 Don't just come here and expect me to feed it all to you. 132 00:07:36,170 --> 00:07:39,080 We will answer questions in this class. 133 00:07:39,080 --> 00:07:43,300 And you will have a chance to ask me questions. 134 00:07:43,300 --> 00:07:46,240 But to make sure you're reading, I am sometimes just going 135 00:07:46,240 --> 00:07:49,275 to say, what's the answer to that question? 136 00:07:52,300 --> 00:07:56,050 You'll all be embarrassed from time to time, 137 00:07:56,050 --> 00:07:59,000 but it gets you to read. 138 00:07:59,000 --> 00:08:02,380 I can also use quizzes for that, but that takes up class time, 139 00:08:02,380 --> 00:08:03,595 takes up discussion time. 140 00:08:03,595 --> 00:08:06,920 So we're not going to have time to do too many quizzes. 141 00:08:06,920 --> 00:08:09,460 I will let in advance when we're going to have one. 142 00:08:12,190 --> 00:08:16,280 So let's go through the questions. 143 00:08:16,280 --> 00:08:19,020 And I know this is the first class. 144 00:08:19,020 --> 00:08:21,410 We had a little trouble getting the book online. 145 00:08:21,410 --> 00:08:25,360 MIT Press was going to do it, as you probably know. 146 00:08:25,360 --> 00:08:29,810 And they ended up not being satisfied with their set-up 147 00:08:29,810 --> 00:08:31,730 for textbooks for a specific class. 148 00:08:31,730 --> 00:08:36,120 They have a deal with the libraries to make their books, 149 00:08:36,120 --> 00:08:38,730 their ebooks-- but mine isn't actually even out 150 00:08:38,730 --> 00:08:42,950 yet, so that will come. 151 00:08:42,950 --> 00:08:47,010 March 28 is when we can actually get the book, the print book. 152 00:08:47,010 --> 00:08:50,565 And after a few classes, I'll get all the names of you 153 00:08:50,565 --> 00:08:54,090 who expect to stay in the class or for other reasons want 154 00:08:54,090 --> 00:08:55,620 the book. 155 00:08:55,620 --> 00:08:59,960 And I will give that list to the guy at the MIT Press bookstore, 156 00:08:59,960 --> 00:09:04,130 to make sure he holds those for you guys. 157 00:09:04,130 --> 00:09:06,650 And then, anybody else that comes in, 158 00:09:06,650 --> 00:09:08,620 he'll have to have extra copies for them. 159 00:09:13,650 --> 00:09:15,770 Should brain structures and their organization 160 00:09:15,770 --> 00:09:18,860 make sense to you? 161 00:09:18,860 --> 00:09:21,590 Because it seems a little arbitrary 162 00:09:21,590 --> 00:09:24,360 a lot of times when you're studying brain structure. 163 00:09:24,360 --> 00:09:26,500 What kind of sense should it make? 164 00:09:26,500 --> 00:09:28,822 What kind of sense do you want it to make? 165 00:09:31,650 --> 00:09:33,960 How would you answer that? 166 00:09:33,960 --> 00:09:38,350 I want it to make sense in terms of evolution 167 00:09:38,350 --> 00:09:41,760 and in terms of development and in terms of function. 168 00:09:41,760 --> 00:09:44,910 I want the connections we talk about, most of them, 169 00:09:44,910 --> 00:09:46,930 to make some kind of functional sense. 170 00:09:46,930 --> 00:09:49,320 It will help you remember it. 171 00:09:49,320 --> 00:09:54,890 And you will build, gradually, this outline in your mind. 172 00:09:54,890 --> 00:09:59,980 And if it doesn't seem to make any sense, bring it up. 173 00:09:59,980 --> 00:10:03,760 Just tell me, it doesn't make any sense, OK? 174 00:10:03,760 --> 00:10:06,790 Put me on the spot. 175 00:10:06,790 --> 00:10:12,280 So, could somebody define central nervous system for me? 176 00:10:12,280 --> 00:10:12,904 Yes. 177 00:10:12,904 --> 00:10:13,820 AUDIENCE: [INAUDIBLE]. 178 00:10:22,730 --> 00:10:23,610 . 179 00:10:23,610 --> 00:10:26,410 PROFESSOR: So brain and spinal cord. 180 00:10:26,410 --> 00:10:28,950 The brain is in the skull. 181 00:10:28,950 --> 00:10:34,570 The word encephalon means in the skull. 182 00:10:34,570 --> 00:10:38,260 So we talk about the different main parts of the brain 183 00:10:38,260 --> 00:10:44,080 as prosencephalon, mesencephalon, rhombencephalon, 184 00:10:44,080 --> 00:10:49,090 the different three major brain vesicles in the skull. 185 00:10:49,090 --> 00:10:57,320 And then the marrow, the center of the spinal column, enclosed 186 00:10:57,320 --> 00:11:03,570 by the vertebrae there's the spinal cord or the medulla 187 00:11:03,570 --> 00:11:05,820 spinalis. 188 00:11:05,820 --> 00:11:08,150 That's why the caudal end of the hindbrain 189 00:11:08,150 --> 00:11:14,230 is actually the medulla oblongata, the elongated center 190 00:11:14,230 --> 00:11:17,280 medulla of the spinal cord. 191 00:11:21,340 --> 00:11:23,940 So here are pictures of it. 192 00:11:23,940 --> 00:11:25,315 This is one from [INAUDIBLE]. 193 00:11:28,650 --> 00:11:33,870 This is from a dissection at a medical school 194 00:11:33,870 --> 00:11:38,520 museum in [INAUDIBLE], Switzerland that I visited. 195 00:11:38,520 --> 00:11:40,110 They have a wonderful museum there. 196 00:11:40,110 --> 00:11:44,920 And this is a dissection of a child who died. 197 00:11:44,920 --> 00:11:51,580 And they have exposed the whole spinal cord and the roots 198 00:11:51,580 --> 00:11:56,910 and the brain, where they sectioned part of it there. 199 00:11:56,910 --> 00:12:03,960 This is one where-- you know why that 200 00:12:03,960 --> 00:12:08,200 looks so different from this one? 201 00:12:08,200 --> 00:12:11,300 What's different there? 202 00:12:11,300 --> 00:12:16,280 It's encased by the dura mater. 203 00:12:16,280 --> 00:12:20,870 The dura is the tough mother, the canvas-like covering 204 00:12:20,870 --> 00:12:23,290 of the brain, the outer meningeal layer. 205 00:12:27,020 --> 00:12:31,310 And we found this picture after my book. 206 00:12:31,310 --> 00:12:33,590 I would have liked to use this in my book. 207 00:12:33,590 --> 00:12:39,760 I've actually used these, but this one probably 208 00:12:39,760 --> 00:12:41,710 will be in the next edition because it's 209 00:12:41,710 --> 00:12:46,610 such a beautiful dissection of the adult human spinal cord 210 00:12:46,610 --> 00:12:52,230 and attached to the brain with the nerve roots, of course, 211 00:12:52,230 --> 00:12:52,845 all cut off. 212 00:12:52,845 --> 00:12:55,350 These would lead to the whole network 213 00:12:55,350 --> 00:12:56,978 of the peripheral nervous system. 214 00:12:59,970 --> 00:13:04,270 So now, beginning at the caudal end of the CNS, 215 00:13:04,270 --> 00:13:06,940 what are the names of all the major subdivisions? 216 00:13:06,940 --> 00:13:14,240 Let's name them-- the most caudal, spinal cord. 217 00:13:14,240 --> 00:13:15,322 So what's just above it? 218 00:13:15,322 --> 00:13:16,780 I've already mentioned it in class. 219 00:13:16,780 --> 00:13:19,760 I've actually mentioned all the main answers here. 220 00:13:19,760 --> 00:13:22,320 But I want to see now. 221 00:13:22,320 --> 00:13:24,570 You've had 901. 222 00:13:24,570 --> 00:13:26,940 You've had brain pics before. 223 00:13:26,940 --> 00:13:29,290 You should know all these. 224 00:13:29,290 --> 00:13:31,040 So don't be too embarrassed if you forget. 225 00:13:31,040 --> 00:13:34,460 The neuroanatomy doesn't stick with some people very well, 226 00:13:34,460 --> 00:13:36,500 but that's why you're taking the class, right? 227 00:13:36,500 --> 00:13:37,950 So what's above the spinal cord? 228 00:13:41,550 --> 00:13:42,800 The brain stem. 229 00:13:42,800 --> 00:13:47,440 The brain stem is a general name for everything 230 00:13:47,440 --> 00:13:50,510 in the encephalon, inside the skull, 231 00:13:50,510 --> 00:13:54,380 that's not cerebral hemispheres. 232 00:13:54,380 --> 00:13:58,190 These are cerebral hemispheres. 233 00:13:58,190 --> 00:14:01,400 There's the cerebellum. 234 00:14:01,400 --> 00:14:03,500 Those are the cortical areas. 235 00:14:03,500 --> 00:14:06,300 It's everything else that's not those two things. 236 00:14:09,210 --> 00:14:17,300 So let's start at the bottom and name the most caudal one, 237 00:14:17,300 --> 00:14:19,965 simplest in English; hindbrain, midbrain, forebrain. 238 00:14:22,880 --> 00:14:27,060 The hindbrain, the lower part, is the medulla oblongata. 239 00:14:27,060 --> 00:14:31,080 The rostral part is often called the pons, 240 00:14:31,080 --> 00:14:32,630 just because of the structure called 241 00:14:32,630 --> 00:14:35,510 the pons that's located there. 242 00:14:35,510 --> 00:14:38,740 And we'll be talking about that and its connections. 243 00:14:38,740 --> 00:14:41,785 And then above the hindbrain, the midbrain. 244 00:14:44,510 --> 00:14:48,530 And we'll be studying that in a special unit, 245 00:14:48,530 --> 00:14:52,380 and it will come back in various chapters of the book. 246 00:14:52,380 --> 00:14:55,190 And then, the forebrain, but what 247 00:14:55,190 --> 00:14:59,150 are the major parts of the forebrain? 248 00:14:59,150 --> 00:15:02,740 The hemispheres we've already named, cerebral hemispheres. 249 00:15:02,740 --> 00:15:05,130 That's the endbrain. 250 00:15:05,130 --> 00:15:09,370 It contains a little more than the hemispheres. 251 00:15:09,370 --> 00:15:12,380 It contains the olfactory bulbs and what 252 00:15:12,380 --> 00:15:15,170 we call the basal forebrain. 253 00:15:15,170 --> 00:15:21,140 And what's in between the endbrain and the midbrain? 254 00:15:21,140 --> 00:15:22,840 The tween brain, of course. 255 00:15:22,840 --> 00:15:25,590 The between brain. 256 00:15:25,590 --> 00:15:28,020 Sure, it's between the midbrain and the endbrain. 257 00:15:28,020 --> 00:15:30,870 It's also between the hemispheres. 258 00:15:30,870 --> 00:15:34,680 The hemispheres kind of blossom out of the tween brain. 259 00:15:34,680 --> 00:15:40,650 All right, so here's a picture of the embryonic neural tube, 260 00:15:40,650 --> 00:15:43,480 where I've taken the developing hemispheres 261 00:15:43,480 --> 00:15:45,940 and I've sort of pushed them apart. 262 00:15:45,940 --> 00:15:50,480 So you can see the thin of what we call the roof plate here 263 00:15:50,480 --> 00:15:52,640 on the rhombencephalon. 264 00:15:52,640 --> 00:15:57,900 There you see the hindbrain right there. 265 00:15:57,900 --> 00:16:03,060 And you see how it's got that sort of one-cell thick membrane 266 00:16:03,060 --> 00:16:03,910 across the top? 267 00:16:03,910 --> 00:16:05,060 It's a tube. 268 00:16:05,060 --> 00:16:07,940 The whole nervous system is a tube. 269 00:16:07,940 --> 00:16:10,960 But the walls get very thick with development. 270 00:16:10,960 --> 00:16:12,340 This is early in development. 271 00:16:12,340 --> 00:16:14,800 They're not that thick yet. 272 00:16:14,800 --> 00:16:21,050 But that roof plate never gets thick in much of the hindbrain, 273 00:16:21,050 --> 00:16:23,490 only in the rostral part where the cerebellum develop. 274 00:16:23,490 --> 00:16:24,520 Then it gets huge. 275 00:16:27,320 --> 00:16:27,890 Sorry? 276 00:16:27,890 --> 00:16:30,375 AUDIENCE: [INAUDIBLE]? 277 00:16:30,375 --> 00:16:31,500 PROFESSOR: The tween brain. 278 00:16:31,500 --> 00:16:32,690 AUDIENCE: Is that your term? 279 00:16:32,690 --> 00:16:35,500 PROFESSOR: No, no, that's what di-encephalon means. 280 00:16:35,500 --> 00:16:38,320 AUDIENCE: Oh. 281 00:16:38,320 --> 00:16:42,230 PROFESSOR: I'm just giving you here the equivalent 282 00:16:42,230 --> 00:16:48,010 English and classical names. 283 00:16:48,010 --> 00:16:49,215 These are basically Greek. 284 00:16:51,850 --> 00:16:54,540 And the Romans imported a lot of the terms 285 00:16:54,540 --> 00:16:57,640 from the Greek language, and they have their own. 286 00:17:00,900 --> 00:17:02,400 So the other question is here, why 287 00:17:02,400 --> 00:17:06,410 is the hindbrain called the rhombencephalon. 288 00:17:06,410 --> 00:17:10,750 Hindbrain, rhombencephalon-- well, rhombencephalon 289 00:17:10,750 --> 00:17:11,800 doesn't mean hindbrain. 290 00:17:14,349 --> 00:17:15,730 Sorry? 291 00:17:15,730 --> 00:17:19,230 For that rhombic shape there. 292 00:17:19,230 --> 00:17:22,630 It's the shape of the roof plate seen from the top. 293 00:17:22,630 --> 00:17:28,530 And that stretches out like that when the development of the two 294 00:17:28,530 --> 00:17:31,730 develops flexures, bends. 295 00:17:31,730 --> 00:17:34,195 It's like a peapod that you've bent 296 00:17:34,195 --> 00:17:41,630 and it stretches out part of the top there. 297 00:17:41,630 --> 00:17:43,550 So what are the coordinates we use now? 298 00:17:43,550 --> 00:17:47,810 We want directions when we're looking at brain sections, 299 00:17:47,810 --> 00:17:51,920 and we want to know what the common planes of section are. 300 00:17:51,920 --> 00:17:54,960 Of course, we talk about anterior and posterior, 301 00:17:54,960 --> 00:17:56,360 rostral and caudal. 302 00:17:56,360 --> 00:17:58,160 Do those always mean the same thing? 303 00:17:58,160 --> 00:17:59,720 No, not for humans. 304 00:17:59,720 --> 00:18:02,520 They do for most animals. 305 00:18:02,520 --> 00:18:04,790 Now here, anterior and posterior, 306 00:18:04,790 --> 00:18:07,716 same as rostral and caudal. 307 00:18:07,716 --> 00:18:09,880 Do you have trouble remembering those names? 308 00:18:09,880 --> 00:18:12,220 Rostrum, do you know the term rostrum? 309 00:18:12,220 --> 00:18:13,600 He's at the rostrum. 310 00:18:13,600 --> 00:18:16,190 He's at the front. 311 00:18:16,190 --> 00:18:18,980 Caudal actually means tail. 312 00:18:22,650 --> 00:18:25,492 Dorsal, ventral-- dorsal towards the back, 313 00:18:25,492 --> 00:18:26,575 ventral towards the belly. 314 00:18:32,680 --> 00:18:34,690 But look at the human here. 315 00:18:34,690 --> 00:18:37,490 The only way the terms are really equivalent for the human 316 00:18:37,490 --> 00:18:40,710 is when he's in that position. 317 00:18:40,710 --> 00:18:47,220 Because if he's standing up, now ventral is also anterior, 318 00:18:47,220 --> 00:18:49,120 you see? 319 00:18:49,120 --> 00:18:50,050 Not so here. 320 00:18:55,690 --> 00:18:58,210 And it's similar for the bird. 321 00:18:58,210 --> 00:19:02,370 And so that's the reason we normally-- and by the way, 322 00:19:02,370 --> 00:19:07,540 you can use the term oral, too, instead of rostral. 323 00:19:07,540 --> 00:19:12,570 But that's why I prefer just the dorsal, ventral, rostral, 324 00:19:12,570 --> 00:19:15,990 caudal terms because you can use them 325 00:19:15,990 --> 00:19:19,840 right across all the vertebrates, 326 00:19:19,840 --> 00:19:23,180 and even for invertebrates. 327 00:19:23,180 --> 00:19:27,160 And for the planes of section, very simple. 328 00:19:27,160 --> 00:19:30,200 But just notice the synonymous terms. 329 00:19:30,200 --> 00:19:33,750 And I will sometimes, without even thinking, 330 00:19:33,750 --> 00:19:35,710 switch from one of these to the other. 331 00:19:35,710 --> 00:19:41,070 Transverse, frontal, coronal-- the all mean the same thing. 332 00:19:41,070 --> 00:19:43,785 Horizontal always means horizontal. 333 00:19:43,785 --> 00:19:46,010 You have midsaggital and parasaggital. 334 00:19:46,010 --> 00:19:49,740 But parasaggital, people don't bother with that. 335 00:19:49,740 --> 00:19:52,500 They still just call them all saggital, 336 00:19:52,500 --> 00:19:56,105 whether they're midsaggital or parasaggital, at the midline 337 00:19:56,105 --> 00:19:56,995 or off the midline. 338 00:20:00,070 --> 00:20:05,470 And then, oblique sections are just used for special purposes 339 00:20:05,470 --> 00:20:08,545 in order to get certain axons all in the plane of sections 340 00:20:08,545 --> 00:20:09,960 and so forth. 341 00:20:09,960 --> 00:20:14,080 And here I'm just showing-- what you 342 00:20:14,080 --> 00:20:18,050 see here are the drawings that I based the textbook figures on. 343 00:20:18,050 --> 00:20:20,740 We did redraw a lot of them for the book. 344 00:20:20,740 --> 00:20:23,730 But here I just sketched the brains 345 00:20:23,730 --> 00:20:25,465 used in the lab the most, the mouse, rat, 346 00:20:25,465 --> 00:20:27,710 or hamster, from the side. 347 00:20:27,710 --> 00:20:31,080 And showing if you make a series of frontal sections 348 00:20:31,080 --> 00:20:34,310 and cut like that, this would be the horizontal plane. 349 00:20:34,310 --> 00:20:36,110 And then I turn the brain around. 350 00:20:36,110 --> 00:20:37,740 You're looking at it from the front. 351 00:20:37,740 --> 00:20:40,254 The olfactory bulbs in front. 352 00:20:40,254 --> 00:20:45,520 And the sagittal sections would look like that. 353 00:20:45,520 --> 00:20:48,990 So what kind of education tissue makes up the CNS? 354 00:20:48,990 --> 00:20:52,545 It's not really a lump of porridge. 355 00:20:52,545 --> 00:20:57,790 It just looks like that if it's not fixed. 356 00:20:57,790 --> 00:20:59,655 So what kind of tissue is it? 357 00:20:59,655 --> 00:21:03,390 You can say it's ectodermal tissue 358 00:21:03,390 --> 00:21:07,555 because it arises from the embryonic ectoderm. 359 00:21:10,140 --> 00:21:15,850 And part of that ectoderm fronds the central nervous system 360 00:21:15,850 --> 00:21:18,880 and peripheral nervous system. 361 00:21:18,880 --> 00:21:22,250 And we will see that because one of our early topics 362 00:21:22,250 --> 00:21:23,425 is spinal cord development. 363 00:21:29,600 --> 00:21:32,690 When you do histology of nervous system tissue, 364 00:21:32,690 --> 00:21:36,039 it's very much like histology of skin 365 00:21:36,039 --> 00:21:37,330 because the skin is ectodermal. 366 00:21:42,260 --> 00:21:46,060 So how do we define and recognize cell groups? 367 00:21:46,060 --> 00:21:47,670 Anybody? 368 00:21:47,670 --> 00:21:49,350 What do we do? 369 00:21:49,350 --> 00:21:51,700 How were they initially named? 370 00:21:51,700 --> 00:21:58,980 Well, of course dissection, but you can't see a lot of detail 371 00:21:58,980 --> 00:22:02,570 with dissection that you can see with anatomical methods. 372 00:22:02,570 --> 00:22:05,221 Well, what kind of anatomical methods? 373 00:22:05,221 --> 00:22:05,720 Yeah? 374 00:22:08,960 --> 00:22:10,040 Yeah, you. 375 00:22:10,040 --> 00:22:12,090 You were indicating you were going to tell me. 376 00:22:15,380 --> 00:22:16,105 Speak louder. 377 00:22:23,020 --> 00:22:27,010 Anybody, give me some methods. 378 00:22:27,010 --> 00:22:29,000 Sorry? 379 00:22:29,000 --> 00:22:30,670 I can't hear very well. 380 00:22:30,670 --> 00:22:33,300 I can't hear well with any background noise. 381 00:22:33,300 --> 00:22:37,359 I have more trouble than you do, I think, in hearing me. 382 00:22:37,359 --> 00:22:39,630 AUDIENCE: Stains, we can look at stains. 383 00:22:39,630 --> 00:22:44,330 PROFESSOR: Stains, one word, histological stains. 384 00:22:44,330 --> 00:22:48,660 Give me an example of a-- a Nissl stain. 385 00:22:48,660 --> 00:22:51,040 What does it stain for? 386 00:22:51,040 --> 00:22:52,040 Well, a Nissl substance. 387 00:22:52,040 --> 00:22:54,830 Where is the Nissl substance? 388 00:22:54,830 --> 00:22:56,710 In the cell body. 389 00:22:56,710 --> 00:22:59,320 Not very much of it gets into the dendrites, 390 00:22:59,320 --> 00:23:02,960 maybe the large proximal dendrites get a little of it. 391 00:23:02,960 --> 00:23:05,520 And it doesn't enter much of the axon either. 392 00:23:05,520 --> 00:23:07,390 So when we stain for Nissl substance, 393 00:23:07,390 --> 00:23:10,300 we're seeing the cell bodies. 394 00:23:10,300 --> 00:23:14,043 So you'll see whether the neurons are big or small, 395 00:23:14,043 --> 00:23:17,330 and whether they have a lot of Nissl substance or less, 396 00:23:17,330 --> 00:23:20,280 so there'll be dark staining or lighter staining. 397 00:23:20,280 --> 00:23:25,720 And just those properties help us define different cell 398 00:23:25,720 --> 00:23:29,880 groups, and they help us define layers. 399 00:23:29,880 --> 00:23:32,477 So we will see more pictures of that. 400 00:23:32,477 --> 00:23:34,560 There's many pictures in the book of these things. 401 00:23:34,560 --> 00:23:40,070 And you will see more pictures next time and in chapter two. 402 00:23:40,070 --> 00:23:42,620 Some of you have read it already. 403 00:23:42,620 --> 00:23:43,745 What other kinds of stains? 404 00:23:46,810 --> 00:23:51,640 Well, Golgi, but if you just take a more general stain, 405 00:23:51,640 --> 00:23:56,640 other than the Nissl stain, we could stain for fibers. 406 00:23:56,640 --> 00:24:00,270 And the fiber stains might just stain for myelin, 407 00:24:00,270 --> 00:24:02,960 so that's only the thicker myelinated fibers, 408 00:24:02,960 --> 00:24:06,290 but they might stain for all the fibers, 409 00:24:06,290 --> 00:24:08,750 like silver stains for axons. 410 00:24:08,750 --> 00:24:11,390 That gives you a different picture. 411 00:24:11,390 --> 00:24:17,160 Like for example, when I wanted to map the whole neocortex 412 00:24:17,160 --> 00:24:20,640 of the hamster, I found the Nissl substances 413 00:24:20,640 --> 00:24:23,140 not to be all that clear. 414 00:24:23,140 --> 00:24:28,370 I could see boundaries, but it was pretty hard to make out. 415 00:24:28,370 --> 00:24:32,860 So I used a silver stain for axons, 416 00:24:32,860 --> 00:24:37,010 and found suddenly I could really see clear boundaries. 417 00:24:37,010 --> 00:24:42,720 And I was able to map, using a lot of quantitative care 418 00:24:42,720 --> 00:24:46,000 in the histology, I was able to map the cortical areas. 419 00:24:46,000 --> 00:24:51,210 And you'll see results of both of those kinds of methods 420 00:24:51,210 --> 00:24:54,350 applied to mapping different parts of the brain. 421 00:24:57,510 --> 00:25:01,990 If we use the term primitive cellular mechanisms, the way 422 00:25:01,990 --> 00:25:05,330 I do in the book, what's it mean when 423 00:25:05,330 --> 00:25:07,037 we're talking about nervous system? 424 00:25:10,700 --> 00:25:14,770 What is a primitive cellular mechanism? 425 00:25:14,770 --> 00:25:20,080 Basically, I'm talking about mechanisms 426 00:25:20,080 --> 00:25:23,670 that we see in single-celled animals, 427 00:25:23,670 --> 00:25:25,290 that we still see in neurons. 428 00:25:27,950 --> 00:25:31,270 And here I list them, as the way I list them and discuss them 429 00:25:31,270 --> 00:25:33,580 in chapter one. 430 00:25:33,580 --> 00:25:35,850 They're all present in one-celled organisms. 431 00:25:35,850 --> 00:25:39,460 They're retained in the evolution of neurons. 432 00:25:39,460 --> 00:25:42,680 Irritability and conduction-- irritability 433 00:25:42,680 --> 00:25:46,450 means it responds in some way to stimulation, like even just 434 00:25:46,450 --> 00:25:49,480 simple mechanical stimulation, but also other kinds 435 00:25:49,480 --> 00:25:52,200 of stimulation, chemical stimulation, 436 00:25:52,200 --> 00:25:54,370 electrical stimulation. 437 00:25:54,370 --> 00:25:56,720 Something changes in the membrane, 438 00:25:56,720 --> 00:26:00,100 and it conducts those changes to other parts of the cell. 439 00:26:00,100 --> 00:26:01,910 It happens in the amoeba. 440 00:26:01,910 --> 00:26:05,380 It happens in other protozoa. 441 00:26:05,380 --> 00:26:08,620 It happens in neurons. 442 00:26:08,620 --> 00:26:10,220 And then we get specializations. 443 00:26:10,220 --> 00:26:13,150 That happens in single-celled organisms, too. 444 00:26:13,150 --> 00:26:15,880 Parts of the membrane respond better to some stimuli. 445 00:26:19,100 --> 00:26:22,550 And we see that in neurons, of course. 446 00:26:22,550 --> 00:26:26,126 Specializations at the synapse, of course, specializations 447 00:26:26,126 --> 00:26:31,140 for responding to stimulation from the outside world, 448 00:26:31,140 --> 00:26:33,390 movements themselves, specialize in movement. 449 00:26:33,390 --> 00:26:36,300 You say, well, that applies only to muscle cells. 450 00:26:36,300 --> 00:26:38,170 No, it applies to neurons, too. 451 00:26:38,170 --> 00:26:42,020 They have to move a lot when they develop. 452 00:26:42,020 --> 00:26:44,260 And they still use contractile proteins, just 453 00:26:44,260 --> 00:26:46,630 like the muscle cells. 454 00:26:46,630 --> 00:26:51,270 And then secretion, single-cell organisms secrete. 455 00:26:51,270 --> 00:26:56,060 They use that in catching prey, for example. 456 00:26:56,060 --> 00:26:58,080 Secretions-- many neurons specialize. 457 00:26:58,080 --> 00:27:01,350 And even central nervous system neurons, some of them 458 00:27:01,350 --> 00:27:04,600 don't just secrete chemicals at at the synapses, 459 00:27:04,600 --> 00:27:08,910 but they secrete into the bloodstream. 460 00:27:08,910 --> 00:27:11,090 They are neurosecretory cells. 461 00:27:14,150 --> 00:27:16,075 And then parallel channels of information 462 00:27:16,075 --> 00:27:19,150 is some way to integrate different information coming 463 00:27:19,150 --> 00:27:20,710 in different parts. 464 00:27:20,710 --> 00:27:23,140 Single-cell organisms, it's easier for them 465 00:27:23,140 --> 00:27:24,810 because they're all one cell. 466 00:27:24,810 --> 00:27:26,700 When you get a multicellular organism, 467 00:27:26,700 --> 00:27:29,270 especially if it's big, then it becomes a real problem. 468 00:27:29,270 --> 00:27:33,070 How do you integrate different things? 469 00:27:33,070 --> 00:27:34,790 Different stimuli can be contradictory. 470 00:27:37,327 --> 00:27:39,910 Your left hand might be touching one thing, and the right hand 471 00:27:39,910 --> 00:27:41,800 something that doesn't make any sense in terms 472 00:27:41,800 --> 00:27:42,980 of what's in your left hand. 473 00:27:42,980 --> 00:27:44,290 How do you solve a problem? 474 00:27:44,290 --> 00:27:45,800 How do you integrate? 475 00:27:45,800 --> 00:27:48,190 Well, you need connections, the soul 476 00:27:48,190 --> 00:27:50,460 of what we'll be dealing with. 477 00:27:50,460 --> 00:27:54,510 And then the last property, endogenous activity-- 478 00:27:54,510 --> 00:27:57,810 we'll come back to that one. 479 00:27:57,810 --> 00:28:00,840 Can someone answer question 11 for me? 480 00:28:00,840 --> 00:28:03,780 Contrast the meaning of synapse and boutons 481 00:28:03,780 --> 00:28:08,050 in descriptions of neuronal structures. 482 00:28:08,050 --> 00:28:10,090 You find both of them. 483 00:28:10,090 --> 00:28:15,670 You find a bouton near the axon ending, or at the axon ending. 484 00:28:15,670 --> 00:28:17,870 Often many boutons associated with one 485 00:28:17,870 --> 00:28:22,170 axon because it branches and has many ending. 486 00:28:22,170 --> 00:28:25,106 And we talk about synapses. 487 00:28:25,106 --> 00:28:27,480 What is the difference in the way we use those two terms? 488 00:28:32,661 --> 00:28:33,603 AUDIENCE: [INAUDIBLE]. 489 00:28:35,030 --> 00:28:39,745 PROFESSOR: Yeah, let's make an even simpler answer. 490 00:28:39,745 --> 00:28:40,245 Sorry? 491 00:28:44,610 --> 00:28:47,550 You know, I can hardly hear any of you. 492 00:28:47,550 --> 00:28:49,846 AUDIENCE: Is a synapse different after the gap? 493 00:28:49,846 --> 00:28:51,220 PROFESSOR: Yeah, but you're still 494 00:28:51,220 --> 00:28:52,940 not getting the major point. 495 00:28:52,940 --> 00:28:54,370 You're looking at details. 496 00:28:54,370 --> 00:28:56,100 I want the main picture. 497 00:28:56,100 --> 00:28:59,530 What's the difference between a bouton and a synapse? 498 00:28:59,530 --> 00:29:02,780 A bouton can have a lot of synapses. 499 00:29:02,780 --> 00:29:05,610 The synapse is just one little area 500 00:29:05,610 --> 00:29:07,350 of the membrane that's specialized 501 00:29:07,350 --> 00:29:09,850 for it's content and communication 502 00:29:09,850 --> 00:29:10,725 with another cell. 503 00:29:14,300 --> 00:29:16,840 The bouton is the enlargement of part 504 00:29:16,840 --> 00:29:24,470 of the axon where most synapses occur. 505 00:29:24,470 --> 00:29:29,570 So let's say it's an axon going along like this, 506 00:29:29,570 --> 00:29:32,670 and along its way, it has an enlargement, 507 00:29:32,670 --> 00:29:34,650 and then it just keeps going. 508 00:29:34,650 --> 00:29:36,330 And at that enlargement, that would 509 00:29:36,330 --> 00:29:38,560 be the place to look for synapses. 510 00:29:38,560 --> 00:29:44,630 They're called boutons en passage, boutons in passage. 511 00:29:44,630 --> 00:29:48,040 Often we use the French because it sounds so nice. 512 00:29:48,040 --> 00:29:51,480 And that's where the word, of course, bouton 513 00:29:51,480 --> 00:29:56,010 is a French word; bouton, terminal, the terminal bouton. 514 00:29:56,010 --> 00:29:57,850 Now we talked about a bouton a passage. 515 00:30:00,620 --> 00:30:02,570 So it's where synapses are formed usually. 516 00:30:06,010 --> 00:30:09,835 Do all axons end in boutons and synapses? 517 00:30:14,800 --> 00:30:20,300 No, you will see, we'll talk about this different types 518 00:30:20,300 --> 00:30:22,400 of ending. 519 00:30:22,400 --> 00:30:26,080 But we're talking about even peripheral nervous system, 520 00:30:26,080 --> 00:30:28,120 an axon going to a muscle cell, it 521 00:30:28,120 --> 00:30:31,620 ends in a type of enlargement, but there it's 522 00:30:31,620 --> 00:30:33,870 more specialized. 523 00:30:33,870 --> 00:30:36,595 It's the endplate, the muscle endplate. 524 00:30:36,595 --> 00:30:38,980 It's a flat structure, but it has 525 00:30:38,980 --> 00:30:40,635 all the synapses on the muscles. 526 00:30:45,130 --> 00:30:48,240 Next question there, what membrane structure 527 00:30:48,240 --> 00:30:53,210 had to evolve in order for action potentials in axons 528 00:30:53,210 --> 00:30:55,590 to evolve? 529 00:30:55,590 --> 00:30:59,860 You know that dendrites, most of them, 530 00:30:59,860 --> 00:31:01,450 don't conduct action potentials. 531 00:31:01,450 --> 00:31:03,840 A few of them actually do, but not very many. 532 00:31:06,720 --> 00:31:08,630 They conduct differently from axons. 533 00:31:08,630 --> 00:31:11,250 Axons conduct by action potentials. 534 00:31:11,250 --> 00:31:14,720 Now I want to know what membrane structure 535 00:31:14,720 --> 00:31:18,620 had to evolve for this to happen? 536 00:31:18,620 --> 00:31:20,754 Sorry? 537 00:31:20,754 --> 00:31:21,670 AUDIENCE: Myelin? 538 00:31:21,670 --> 00:31:23,930 PROFESSOR: No, no, no, no, myelin 539 00:31:23,930 --> 00:31:28,750 didn't exist when axons first evolved 540 00:31:28,750 --> 00:31:32,930 and when action potentials evolved. 541 00:31:32,930 --> 00:31:38,804 I'm talking about a molecular structure in the membrane. 542 00:31:38,804 --> 00:31:40,280 AUDIENCE: Ion channel? 543 00:31:40,280 --> 00:31:43,330 PROFESSOR: Exactly, a particular type of ion channel, 544 00:31:43,330 --> 00:31:46,080 a voltage-gated ion channel. 545 00:31:46,080 --> 00:31:49,240 It appeared in even jellyfish, which 546 00:31:49,240 --> 00:31:52,250 have been around longer than any chordate. 547 00:31:55,820 --> 00:32:01,620 And that just means that when the membrane potential 548 00:32:01,620 --> 00:32:05,830 changes-- remember the cell is irritable. 549 00:32:05,830 --> 00:32:07,500 It responds to input. 550 00:32:07,500 --> 00:32:13,530 And what's the usual response of a neuron to stimulation? 551 00:32:13,530 --> 00:32:17,900 Or an axon-- take an axon in my arm and I pinch it, 552 00:32:17,900 --> 00:32:21,720 especially if I pinch right here, I get an effect. 553 00:32:24,610 --> 00:32:28,450 I'm causing depolarization, simple word. 554 00:32:28,450 --> 00:32:31,210 Think in terms of the main thing here. 555 00:32:31,210 --> 00:32:33,320 Depolarization, the main response 556 00:32:33,320 --> 00:32:35,810 of a neuronal membrane to stimulation. 557 00:32:39,110 --> 00:32:47,570 So now, what about let's deal with these, 558 00:32:47,570 --> 00:32:51,490 and you'll see examples of that in a minute here. 559 00:32:51,490 --> 00:32:53,180 I want you to be able to contrast 560 00:32:53,180 --> 00:32:55,850 excitatory and inhibitory postsynaptic potential, 561 00:32:55,850 --> 00:32:59,340 you should all be able to do that by now with the studies 562 00:32:59,340 --> 00:32:59,840 you've done. 563 00:32:59,840 --> 00:33:05,035 Unless you're from another department amd 564 00:33:05,035 --> 00:33:07,660 you just wondered what the brain is all about, and you're here. 565 00:33:07,660 --> 00:33:10,210 Well, we'll teach you, but I don't 566 00:33:10,210 --> 00:33:12,830 expect you to be able answer here. 567 00:33:12,830 --> 00:33:14,360 Contrast the nature of conduction 568 00:33:14,360 --> 00:33:19,220 in a dendrite and an axon; just what we were talking about. 569 00:33:19,220 --> 00:33:20,680 And what's the functional purpose 570 00:33:20,680 --> 00:33:25,100 of an active pumping mechanism in the axonal membrane? 571 00:33:25,100 --> 00:33:27,480 Usually people say, oh, action potentials. 572 00:33:27,480 --> 00:33:29,555 And the answer is, no. 573 00:33:29,555 --> 00:33:32,590 It's not its purpose. 574 00:33:32,590 --> 00:33:34,500 So first of all, excitatory, inhibitory 575 00:33:34,500 --> 00:33:36,350 post synaptic potentials, this is 576 00:33:36,350 --> 00:33:41,080 from an introductory biological psychology textbook. 577 00:33:43,660 --> 00:33:47,400 It shows intracellular recordings 578 00:33:47,400 --> 00:33:53,405 with a microelectrode, where they record from this axon. 579 00:34:04,199 --> 00:34:04,990 I'm wondering here. 580 00:34:04,990 --> 00:34:05,490 Yeah. 581 00:34:08,280 --> 00:34:10,760 So the presynaptic recording shows 582 00:34:10,760 --> 00:34:14,270 the action potential, big potential that 583 00:34:14,270 --> 00:34:19,590 goes from minus 60, minus 70, becomes momentarily positive 584 00:34:19,590 --> 00:34:24,699 and then the membrane potential recovers. 585 00:34:24,699 --> 00:34:28,090 And if you record on the other side of the synapse, 586 00:34:28,090 --> 00:34:30,679 you get a little bit of depolarization. 587 00:34:30,679 --> 00:34:32,389 If you're getting depolarization, 588 00:34:32,389 --> 00:34:34,350 it's excitatory. 589 00:34:34,350 --> 00:34:38,020 Why are those two things are equivalent? 590 00:34:38,020 --> 00:34:39,925 Because it moves. 591 00:34:39,925 --> 00:34:46,260 There's one point here where the axon begins, 592 00:34:46,260 --> 00:34:50,250 where if the depolarization, reaches a critical level, 593 00:34:50,250 --> 00:34:53,770 it triggers the action potential. 594 00:34:53,770 --> 00:35:00,760 And these little EPSPs summate at the beginning 595 00:35:00,760 --> 00:35:05,330 of the axon, the axon hillock, we call it. 596 00:35:05,330 --> 00:35:09,130 So the more of them there-- and the conduction in the cell body 597 00:35:09,130 --> 00:35:11,110 is decrimental. 598 00:35:11,110 --> 00:35:14,900 So if it's happening way over here, 599 00:35:14,900 --> 00:35:18,350 and there's a depolarization, it has less effect 600 00:35:18,350 --> 00:35:21,540 on the axon hillock here than something 601 00:35:21,540 --> 00:35:24,974 happening right there. 602 00:35:24,974 --> 00:35:26,390 So it makes a big difference where 603 00:35:26,390 --> 00:35:28,830 the terminal is on the axon. 604 00:35:28,830 --> 00:35:33,340 But the EPSPs look the same everywhere. 605 00:35:33,340 --> 00:35:36,110 They might be a little bigger, or a little smaller, 606 00:35:36,110 --> 00:35:39,090 but they're conducted decrementally 607 00:35:39,090 --> 00:35:41,680 by the dendrites and cell body membrane. 608 00:35:45,480 --> 00:35:49,350 Inhibitory post synaptic potential is opposite. 609 00:35:49,350 --> 00:35:52,330 It's when there's a hyperpolarization, 610 00:35:52,330 --> 00:35:55,460 as you see here. 611 00:35:55,460 --> 00:35:58,800 The membrane, if it was polarized as minus 70, 612 00:35:58,800 --> 00:36:01,690 might go to minus 80. 613 00:36:01,690 --> 00:36:04,760 And it's inhibitory because it takes the membrane further 614 00:36:04,760 --> 00:36:08,980 from the point where an action potential will be triggered. 615 00:36:08,980 --> 00:36:11,610 So let's talk a little bit more about that difference 616 00:36:11,610 --> 00:36:13,810 in conduction in dendrites and axon. 617 00:36:13,810 --> 00:36:19,030 Looking this picture, I drew it without myelin for a reason. 618 00:36:19,030 --> 00:36:23,770 Axons don't need myelin to conduct. 619 00:36:23,770 --> 00:36:28,600 So here I'm drawing functionally equivalent parts 620 00:36:28,600 --> 00:36:31,850 of two neurons, a dorsal root ganglion 621 00:36:31,850 --> 00:36:36,000 cell that conducts from the body surface, where there are 622 00:36:36,000 --> 00:36:39,740 endings here, and then the long axon 623 00:36:39,740 --> 00:36:43,510 goes right by the cell body into the central nervous system, 624 00:36:43,510 --> 00:36:47,760 where it ends in terminals with synapses 625 00:36:47,760 --> 00:36:51,700 on the cells, secondary sensory neurons. 626 00:36:51,700 --> 00:36:53,320 So it's a sensory neuron. 627 00:36:53,320 --> 00:36:54,920 And here I have a motor neuron. 628 00:36:54,920 --> 00:36:59,580 So here, you're inside the CNS, and there is the cell body. 629 00:36:59,580 --> 00:37:03,880 There is the axon going to a muscle cell. 630 00:37:03,880 --> 00:37:17,580 So this part of both of those cells is the receptive part. 631 00:37:17,580 --> 00:37:20,550 This part, where I show the arrows, is the conductive part. 632 00:37:20,550 --> 00:37:23,868 And here transmissions occur in, the transmission part. 633 00:37:32,660 --> 00:37:38,010 And so now let's take a little piece of that. 634 00:37:38,010 --> 00:37:42,670 First of all, the conduction here-- now, in some cases, 635 00:37:42,670 --> 00:37:44,640 the axon might begin further out. 636 00:37:44,640 --> 00:37:47,840 But here, I have it at the beginning right here. 637 00:37:47,840 --> 00:37:50,240 You get decremental conduction there. 638 00:37:50,240 --> 00:37:52,980 What are the characteristics of decremental conduction, other 639 00:37:52,980 --> 00:37:54,705 than the fact that gets less and less 640 00:37:54,705 --> 00:37:58,214 the further away from the sight of stimulation you get? 641 00:37:58,214 --> 00:37:59,880 The other characteristic you should know 642 00:37:59,880 --> 00:38:06,660 is it's very, very fast, almost instantaneous. 643 00:38:06,660 --> 00:38:11,180 Not like light, but it's close, very fast. 644 00:38:11,180 --> 00:38:15,480 And then the point where the action potential 645 00:38:15,480 --> 00:38:17,300 begins, what is an action potential? 646 00:38:21,410 --> 00:38:22,790 Here I pictured it. 647 00:38:22,790 --> 00:38:26,400 I've taken a snapshot of it at one little plane 648 00:38:26,400 --> 00:38:29,720 and enlarged the tube or the axon, 649 00:38:29,720 --> 00:38:35,970 and I'm just showing how ion distributions are polarizing 650 00:38:35,970 --> 00:38:41,000 the membrane, positive on the outside, mainly because 651 00:38:41,000 --> 00:38:46,290 of the accumulation of sodium ions, negative on the inside. 652 00:38:46,290 --> 00:38:49,520 There are potassium ions in there that are positive also. 653 00:38:49,520 --> 00:38:51,890 But a lot of name are going to be charged anions, 654 00:38:51,890 --> 00:38:56,560 large ones, and [INAUDIBLE] here. 655 00:39:00,250 --> 00:39:04,350 What happens when, at the beginning of the action 656 00:39:04,350 --> 00:39:09,530 potential, there's an implosion of sodium ions? 657 00:39:09,530 --> 00:39:11,970 Momentarily reverses the potential. 658 00:39:11,970 --> 00:39:17,210 This curve matches that piece of axon. 659 00:39:17,210 --> 00:39:19,780 So there's the beginning of the action potential. 660 00:39:19,780 --> 00:39:24,070 The sodium ions rush in, an implosion of sodium ions. 661 00:39:24,070 --> 00:39:27,750 The potential, remember, reverses, momentarily, 662 00:39:27,750 --> 00:39:30,160 and then it rapidly recovers. 663 00:39:30,160 --> 00:39:32,790 And the first reason it starts recovering 664 00:39:32,790 --> 00:39:35,670 is potassium ion channels are also voltage-gated, 665 00:39:35,670 --> 00:39:40,240 and so potassium, which is in high concentration inside, 666 00:39:40,240 --> 00:39:41,230 rushes out. 667 00:39:41,230 --> 00:39:44,650 The channels open up. 668 00:39:44,650 --> 00:39:46,560 You see, it's a semipermeable membrane. 669 00:39:46,560 --> 00:39:50,780 It's not-- all these ions can't get through very rapidly, 670 00:39:50,780 --> 00:39:54,470 unless the channels open up. 671 00:39:54,470 --> 00:39:57,984 So that's why the voltage-gated ion channels are so important. 672 00:39:57,984 --> 00:39:59,650 And then so then, the membrane recovers. 673 00:40:03,130 --> 00:40:08,200 And there's another way to look at that membrane, 674 00:40:08,200 --> 00:40:11,740 where I show the polarization indicated a lot of sodium ions 675 00:40:11,740 --> 00:40:12,580 on the outside. 676 00:40:12,580 --> 00:40:14,520 There's also chloride ions. 677 00:40:14,520 --> 00:40:16,540 And then, in the inside the negatively charged 678 00:40:16,540 --> 00:40:19,170 anions, the big ones that don't pass through the membrane 679 00:40:19,170 --> 00:40:24,730 at all, and the positively charged potassium ions. 680 00:40:24,730 --> 00:40:27,430 But there are molecules in the membrane, 681 00:40:27,430 --> 00:40:29,720 I'm just showing a couple of sites here, 682 00:40:29,720 --> 00:40:34,480 we call the sodium potassium pump. 683 00:40:34,480 --> 00:40:40,090 It's always moving sodium ions out and potassium ions in. 684 00:40:40,090 --> 00:40:44,230 Because with a lot of action potentials, 685 00:40:44,230 --> 00:40:47,930 you basically lose that concentration 686 00:40:47,930 --> 00:40:50,630 of sodium on the outside and potassium on the inside 687 00:40:50,630 --> 00:40:53,510 if you get a lot of action potentials. 688 00:40:53,510 --> 00:40:56,220 So eventually, it'll just stop. 689 00:40:56,220 --> 00:41:02,030 Unless, you use energy to redistribute those ions. 690 00:41:02,030 --> 00:41:04,620 And that's why we need an active pumping mechanism. 691 00:41:11,900 --> 00:41:16,920 So now we've answered those questions, at least tried to. 692 00:41:16,920 --> 00:41:18,320 Where's the dorsal root ganglia? 693 00:41:18,320 --> 00:41:19,370 I've mentioned it here. 694 00:41:22,290 --> 00:41:26,790 Actually, I said a dorsal root ganglia cell. 695 00:41:26,790 --> 00:41:29,110 Let's answer that a little better, talk 696 00:41:29,110 --> 00:41:32,560 about the oligodendrocytes and Schwann cells. 697 00:41:32,560 --> 00:41:34,089 Somebody already mentioned myelin. 698 00:41:34,089 --> 00:41:35,630 These are the cells that make myelin. 699 00:41:40,060 --> 00:41:44,240 And then I want to talk about the main function of the myelin 700 00:41:44,240 --> 00:41:45,910 sheath. 701 00:41:45,910 --> 00:41:49,040 First of all, what's the dorsal root ganglia? 702 00:41:49,040 --> 00:41:50,600 This is a picture from [INAUDIBLE] 703 00:41:50,600 --> 00:41:51,930 that I put in the book. 704 00:41:51,930 --> 00:41:54,240 Here you see in an earthworm and mollusk, 705 00:41:54,240 --> 00:41:57,090 primary sensory neurons, the neurons responding 706 00:41:57,090 --> 00:41:58,130 to the outside world. 707 00:41:58,130 --> 00:42:02,220 These are neurons at the surface layer of the body, 708 00:42:02,220 --> 00:42:04,160 so in the skin of the animal. 709 00:42:04,160 --> 00:42:06,270 Here are the cell primary sensory neurons 710 00:42:06,270 --> 00:42:08,520 right in the epothelium. 711 00:42:08,520 --> 00:42:10,980 Here, the cell body below the epothelium, 712 00:42:10,980 --> 00:42:16,036 but it extends right out into the epothelium. 713 00:42:19,160 --> 00:42:23,360 But as soon as you get to the vertebrates-- 714 00:42:23,360 --> 00:42:26,320 this is the central ganglion here. 715 00:42:26,320 --> 00:42:28,010 We don't talk really about a CNS, 716 00:42:28,010 --> 00:42:30,446 but sometimes we do, just because 717 00:42:30,446 --> 00:42:31,820 of similarity to the vertebrates. 718 00:42:35,620 --> 00:42:39,680 Here's a fish and amphibian, reptile, bird, or mammal. 719 00:42:39,680 --> 00:42:43,640 The fish has these bipolar cells that 720 00:42:43,640 --> 00:42:45,140 contain the primary sensory neuron, 721 00:42:45,140 --> 00:42:47,800 and they are collected in a ganglia. 722 00:42:47,800 --> 00:42:50,410 You talk about a collection of cells 723 00:42:50,410 --> 00:42:54,590 outside the central nervous system as ganglia. 724 00:42:54,590 --> 00:43:01,200 So here, in us and in these other mammals and also 725 00:43:01,200 --> 00:43:05,450 amphibians and reptiles, the primary sensory neurons 726 00:43:05,450 --> 00:43:08,785 carry input from the skin are in a dorsal root ganglion. 727 00:43:08,785 --> 00:43:14,160 From the dorsal roots because the roots of the spinal nerves 728 00:43:14,160 --> 00:43:18,510 that enter the CNS will always divide. 729 00:43:18,510 --> 00:43:23,050 The more dorsal one contains the sensory axons, the more ventral 730 00:43:23,050 --> 00:43:27,590 ones, the motor axons going to the muscles. 731 00:43:27,590 --> 00:43:31,820 So that's the dorsal root ganglia. 732 00:43:31,820 --> 00:43:34,120 So now what about oligodendrocytes 733 00:43:34,120 --> 00:43:35,110 and Scwann cells. 734 00:43:39,110 --> 00:43:45,300 When axons acquire myelin, it is the Schwann cell 735 00:43:45,300 --> 00:43:49,830 that myelinites these axons of the periphery, 736 00:43:49,830 --> 00:43:52,550 the peripheral nervous system. 737 00:43:52,550 --> 00:43:55,860 But as soon as you enter the central nervous system, 738 00:43:55,860 --> 00:43:58,240 it's really a very different type of tissue, 739 00:43:58,240 --> 00:44:01,490 and you get a different glial cell making the myelin. 740 00:44:01,490 --> 00:44:03,786 It's now an oligodendrocyte. 741 00:44:03,786 --> 00:44:05,160 There are other differences, too. 742 00:44:05,160 --> 00:44:11,120 One Schwann cell will form the myelin in one little stretch. 743 00:44:11,120 --> 00:44:13,610 And then there will be a little place with no myelin. 744 00:44:13,610 --> 00:44:17,090 And then another Schwann cell wil myelinate the next segment. 745 00:44:17,090 --> 00:44:22,720 In the CNS, one oligodendrocyte can myelinate or form 746 00:44:22,720 --> 00:44:27,430 a segment of myelin in a whole bunch of axons nearby, 747 00:44:27,430 --> 00:44:28,760 so quite different. 748 00:44:28,760 --> 00:44:32,030 But the function is quite similar. 749 00:44:32,030 --> 00:44:33,950 What is the function? 750 00:44:33,950 --> 00:44:35,765 It's a kind of insulator. 751 00:44:35,765 --> 00:44:39,910 It prevents ion flow. 752 00:44:39,910 --> 00:44:42,160 The ions can't flow through the membrane 753 00:44:42,160 --> 00:44:44,162 where the myelin is there. 754 00:44:44,162 --> 00:44:44,870 It's a tight fit. 755 00:44:47,720 --> 00:44:53,740 So if you get depolarization just before myelin begins-- 756 00:44:53,740 --> 00:44:58,390 if we're talking here about space, so at one end-- 757 00:44:58,390 --> 00:45:00,990 you get depolarization. 758 00:45:00,990 --> 00:45:01,895 What happens? 759 00:45:01,895 --> 00:45:04,860 It triggers the action potential right there 760 00:45:04,860 --> 00:45:06,990 on that little piece of bare axon. 761 00:45:06,990 --> 00:45:13,010 And then, the only way I can conduct down the axon 762 00:45:13,010 --> 00:45:19,320 is by a flow of ion by decremental conduction, 763 00:45:19,320 --> 00:45:23,030 until it reaches the next node where there's no myelin. 764 00:45:23,030 --> 00:45:29,610 And if the decrement of the depolarization isn't so great, 765 00:45:29,610 --> 00:45:31,490 it will depolarize that membrane, 766 00:45:31,490 --> 00:45:33,990 trigger an action potential there. 767 00:45:33,990 --> 00:45:36,550 And then same thing will happen, and the conduction 768 00:45:36,550 --> 00:45:41,430 will go bloop, bloop, bloop, bloop, like jumps. 769 00:45:41,430 --> 00:45:45,110 That's what saltatory conduction is. 770 00:45:45,110 --> 00:45:47,070 So [INAUDIBLE] means dumps. 771 00:45:47,070 --> 00:45:50,610 OK And that's why it speeds up, because 772 00:45:50,610 --> 00:45:55,180 the decremental conduction is very fast, like I said before. 773 00:45:55,180 --> 00:45:57,099 The action potential is not so fast 774 00:45:57,099 --> 00:45:58,265 that it's self-regenerating. 775 00:46:00,840 --> 00:46:04,910 So in a picture like this, you just 776 00:46:04,910 --> 00:46:07,450 get this continuous movement of the action potential, 777 00:46:07,450 --> 00:46:09,950 all the way down the axon. 778 00:46:09,950 --> 00:46:12,070 But it's limited in how fast it can go. 779 00:46:12,070 --> 00:46:16,340 It goes faster if the axon's bigger. 780 00:46:16,340 --> 00:46:19,470 So in animals without myelin, the axons 781 00:46:19,470 --> 00:46:21,725 get huge if they need rapid conduction, 782 00:46:21,725 --> 00:46:24,740 for an escape response. 783 00:46:24,740 --> 00:46:27,050 But we don't have-- mammals generally 784 00:46:27,050 --> 00:46:30,620 don't have such huge axons. 785 00:46:30,620 --> 00:46:35,090 It would be very-- it would cost too much energy and space. 786 00:46:35,090 --> 00:46:37,600 The myelin was the invention that solved that problem. 787 00:46:43,050 --> 00:46:46,120 Receptor cells, I said many receptor cells are not actually 788 00:46:46,120 --> 00:46:48,620 neurons. 789 00:46:48,620 --> 00:46:50,120 So how do they differ from neurons? 790 00:46:50,120 --> 00:46:53,320 How do they interactive with neurons? 791 00:46:53,320 --> 00:46:55,740 They depolarize, just like neurons. 792 00:46:55,740 --> 00:46:59,880 But they don't have the membrane of an axon. 793 00:46:59,880 --> 00:47:03,360 They don't have any action potentials, 794 00:47:03,360 --> 00:47:08,200 but their depolarization affects neurons that contact them, 795 00:47:08,200 --> 00:47:12,490 and can trigger an action potential in those neurons. 796 00:47:12,490 --> 00:47:14,510 So that's a receptor cell. 797 00:47:14,510 --> 00:47:17,675 Some receptors, like in the nasal epithelium 798 00:47:17,675 --> 00:47:21,860 or olfactory receptors, the primary sensory cell 799 00:47:21,860 --> 00:47:22,590 is a receptor. 800 00:47:25,640 --> 00:47:28,720 You have the same thing in the retina, where 801 00:47:28,720 --> 00:47:30,570 the specialization is even greater. 802 00:47:34,090 --> 00:47:38,450 And here's just a list of various specializations. 803 00:47:38,450 --> 00:47:41,240 You already should know about various kinds. 804 00:47:41,240 --> 00:47:43,660 Some of them here are mechanical in nature, 805 00:47:43,660 --> 00:47:47,590 also response to light, chemicals, to heat or cold 806 00:47:47,590 --> 00:47:52,260 are all specialized receptor cells, 807 00:47:52,260 --> 00:47:54,977 except in the case of chemicals, where it's the neuron itself. 808 00:47:54,977 --> 00:47:56,560 But it's still a specialized receptor. 809 00:48:00,800 --> 00:48:05,500 What kind of molecules are actin and myosin? 810 00:48:05,500 --> 00:48:09,010 What kind of molecule is that that we're talking about? 811 00:48:09,010 --> 00:48:11,780 Contractal porteins. 812 00:48:11,780 --> 00:48:16,055 When is actin found most abundantly in neurons? 813 00:48:19,530 --> 00:48:23,860 During development, when the axon's growing. 814 00:48:23,860 --> 00:48:25,950 The axon has to move a lot. 815 00:48:25,950 --> 00:48:28,780 The growth cone is very active. 816 00:48:28,780 --> 00:48:31,195 And we will see that when we study development. 817 00:48:33,840 --> 00:48:36,680 You should know about the Otto Loewi's discovery. 818 00:48:36,680 --> 00:48:38,880 Don't have time to describe his dream. 819 00:48:38,880 --> 00:48:40,140 I like to describe it. 820 00:48:40,140 --> 00:48:41,820 It's a lot of fun. 821 00:48:41,820 --> 00:48:42,950 But you should read. 822 00:48:42,950 --> 00:48:45,260 I have a little bit in the book about it. 823 00:48:45,260 --> 00:48:49,950 And you can find things online very easily. 824 00:48:49,950 --> 00:48:53,780 He discovered-- he didn't know he was discovering 825 00:48:53,780 --> 00:48:56,740 acetylcholine and norepinephrine, 826 00:48:56,740 --> 00:48:58,280 but that's what it was. 827 00:48:58,280 --> 00:49:00,260 That's what the molecules turned out to be. 828 00:49:00,260 --> 00:49:06,280 He was the one who settled a big argument in neuroscience 829 00:49:06,280 --> 00:49:08,660 in the early part of the 20th century 830 00:49:08,660 --> 00:49:11,220 about whether conduction in synapse 831 00:49:11,220 --> 00:49:13,570 was electrical or chemical. 832 00:49:13,570 --> 00:49:17,390 And there were a lot of arguments on both sides. 833 00:49:17,390 --> 00:49:21,570 He proved that-- now we know they both exist, 834 00:49:21,570 --> 00:49:24,590 but for the most part, most synapses, 835 00:49:24,590 --> 00:49:26,886 the conduction is the transmission 836 00:49:26,886 --> 00:49:28,510 from one cell to the other is chemical. 837 00:49:28,510 --> 00:49:31,740 He discovered that in this experiment on frogs. 838 00:49:34,720 --> 00:49:40,070 By just stimulating the axon of a heart, 839 00:49:40,070 --> 00:49:45,640 and accelerator nerve, one heart in a Petri dish, 840 00:49:45,640 --> 00:49:47,820 taking a little fluid from that Petri dish 841 00:49:47,820 --> 00:49:49,362 and putting it in another Petri dish, 842 00:49:49,362 --> 00:49:50,778 here he hadn't stimulated a nerve, 843 00:49:50,778 --> 00:49:52,280 but the heart speeded up anyway. 844 00:49:59,490 --> 00:50:03,180 The reason I said it is high and maybe a few of you 845 00:50:03,180 --> 00:50:05,990 want to go to the [INAUDIBLE]. 846 00:50:05,990 --> 00:50:10,260 [INAUDIBLE] didn't discover, didn't talk about-- 847 00:50:10,260 --> 00:50:13,866 I wanted you to read this and you ask me questions about it. 848 00:50:13,866 --> 00:50:15,240 If there's anything about the way 849 00:50:15,240 --> 00:50:17,690 I portrayed synapses and their various types 850 00:50:17,690 --> 00:50:19,360 in the central nervous system. 851 00:50:19,360 --> 00:50:21,640 The hardest thing is probably the concept 852 00:50:21,640 --> 00:50:25,840 of presynaptic facilitation and inhibition. 853 00:50:25,840 --> 00:50:31,570 So, see if you can get some understanding of that. 854 00:50:31,570 --> 00:50:33,050 The rest of this, I think, is quite 855 00:50:33,050 --> 00:50:37,970 clear from the book, endogenous activity also. 856 00:50:37,970 --> 00:50:39,720 Just read it in the book. 857 00:50:39,720 --> 00:50:43,550 You can look at the slides to know what I'm stressing here. 858 00:50:43,550 --> 00:50:48,930 And these concepts will recur later in the class.