Diencephalon Anatomy (Thalamus, Epithalamus, Subthalamus, Metathalamus, Hypothalamus) — Transcript

Full transcript

1. 0:01What’s up.
2. 0:03Meditay here.
3. 0:05Let’s continue the anatomy of the Central Nervous System.
4. 0:08In this segment, we’ll cover the complete anatomy of the different parts of the Diencephalon.
5. 0:13So the central nervous system consists of two parts: the encephalon and the spinal cord.
6. 0:18The encephalon is then further divided into specific parts.
7. 0:22We have the brainstem, which consists of the medulla, pons, and the Midbrain or the mesencephalon.
8. 0:27We have the cerebellum back here, then the Diencephalon and the telencephalon.
9. 0:31Our focus in this video is going to be the Diencephalon, which is here.
10. 0:35So in this video, we’re first going to look at the topography of the Diencephalon.
11. 0:39Basically, understand where is it?
12. 0:42What parts are considered the Diencephalon?
13. 0:44And what’s the orientation between these parts?
14. 0:46After that, we will cover the actual anatomy of all the structures that make up the Diencephalon.
15. 0:51But let’s orientate and understand their relationship first before doing so.
16. 0:57Alright.
17. 0:58Here you see Pons, Medulla, Cerebellum, and the Spinal Cord.
18. 1:02And if we remove one side of the hemisphere, we’ll be able to see the Midbrain.
19. 1:07And right above the Midbrain, we have our Diencephalon.
20. 1:10So the Diencephalon is a group of nerve nuclei that surrounds the Third Ventricle.
21. 1:15SO let’s repeat the ventricular system a little bit.
22. 1:18I’m sure you remember the fourth Ventricle, which continues down as the central canal.
23. 1:22And continues upwards as the aqueduct of the Midbrain, which leads into the 3rd Ventricle.
24. 1:27So again the Diencephalon surrounds the 3rd Ventricle.
25. 1:31And above the third Ventricle, on either side, we have the lateral ventricles.
26. 1:35Alright.
27. 1:36So the Diencephalon surrounds the third Ventricle, and its job is to connect different parts
28. 1:42of the telencephalon, with the brainstem.
29. 1:45It’s like the post office of our brain, directing the signals to the right place.
30. 1:50So let’s now remove the surrounding structures that are not significant to us yet, and orientate
31. 1:55around the different parts of the Diencephalon.
32. 1:58So the Diencephalon consists of 5 parts.
33. 2:01And that includes the Thalamus, Epithalamus, Subthalamus, Metathalamus, and Hypothalamus.
34. 2:07Now I’ve made an orientation scheme that really helped me orientate around the Diencephalon
35. 2:12when I started studying it.
36. 2:14So we can start off here, looking at the Medulla, Pons, Midbrain and Cerebellum.
37. 2:18Now.
38. 2:19Let’s say this is you, right?
39. 2:21A cute little figure swimming around the Cerebrospinal fluid within the fourth Ventricle.
40. 2:26Now we’re going to send you off for some adventure.
41. 2:30So you swim upwards, up through the aqueduct of the Midbrain, until you get to the 3rd
42. 2:35Ventricle.
43. 2:36From your standpoint right now.
44. 2:38When you look to your right and to your left.
45. 2:40You’ll see the Thalamus on either side of the third Ventricle.
46. 2:43So if we go back to our list, Thalamus is our first stop, so let’s go ahead and put
47. 2:48a checkmark there.
48. 2:49Now, you decide to turn around and swim to the very back of the 3rd Ventricle, where
49. 2:55you’ll notice a small pouch handing on the back here like a tail, called the Pineal Gland.
50. 3:00And the Pineal Gland is attached on the backside here through the Habenula.
51. 3:04All of these together form the Epithalamus.
52. 3:07So let’s go ahead and put a checkmark here as well.
53. 3:10Next now, if you duck, kind of look inferiorly to the Thalamus, you’ll find the Subthalamus.
54. 3:16This is another important component of the Diencephalon.
55. 3:19Then on the lateral sides of each thalamus, you’ll find two nuclei called the medial
56. 3:24geniculate body and the lateral geniculate body.
57. 3:28These two nuclei are termed Metathlamus, which is another significant part of the Diencephalon.
58. 3:33Now, you decide to turn around and swim forward, to explore what’s on the anterior side.
59. 3:39And what you see is surprising.
60. 3:41You’ll see grey matter surrounding the anterior portion of the 3rd Ventricle, which is termed
61. 3:46Hypothalamus.
62. 3:47And the Hypothalamus is going to be more of an area that structures are going to be a
63. 3:52part of.
64. 3:53Like the mamillary bodies.
65. 3:54Then there are a bunch of hypothalamic nuclei around this area.
66. 3:59Some of these nuclei, have axons going down as tuber cinetum, which form a stalk called
67. 4:04the infundibulum that connects to the posterior part of the pituitary gland.
68. 4:09Also called neurohypophysis, since it contains neural fibers.
69. 4:13The anterior part of the pituitary gland is not considered a part of the Hypothalamus
70. 4:17since it’s glandular.
71. 4:19It has a different origin during development.
72. 4:22Other parts that are considered a part of the Hypothalamus are the optic chiasm and
73. 4:26the optic tract.
74. 4:27Some sources say they’re their own part of the Diencephalon, called thalamus opticus,
75. 4:32and some sources include them as a part of the Hypothalamus.
76. 4:36In this video we’ll count them as a aprt fo the Hypothalamus, but you know keep that
77. 4:39in mind.
78. 4:40So all of these structures are going to be a part of the Hypothalamus.
79. 4:44Now.
80. 4:45Let’s work our way down the list, starting with the Thalamus.
81. 4:49So I think the best way to learn its anatomy is to go through all the structures one by
82. 4:54one, starting with the external features and then the internal ones.
83. 4:57So the Thalamus is here in green.
84. 4:59And if we look at it from a posterior perspective, you’ll see the thalami on either side right
85. 5:04here.
86. 5:05The most anterior part of each thalami forms a tubercle shape.
87. 5:09We call it the Anterior tubercle.
88. 5:11And the poster end is a more rounded part is called Pulvinar.
89. 5:16And in between the Right and left Thalami, there’s a connection point called Interthalamic
90. 5:21adhesion that connects both thalami together.
91. 5:24So those are the only external features I’m gonna tell you to remember: anterior tubercle,
92. 5:29Pulvinar, and the Interthlamic Adhesion.
93. 5:32Now let’s slice the Thalamus and look at it from a superior perspective.
94. 5:36We’ll see this.
95. 5:38Ok.
96. 5:39This is a thalamus.
97. 5:40The Thalamus is an egg-shaped structure.
98. 5:43And it’s divided into three different kinds of nuclear groups by this little Y-shaped
99. 5:48structure.
100. 5:49This Y shaped structure, is called the Internal Medullary Lamina.
101. 5:52Sometimes it can be referred to as the Medial Medullary Lamina.
102. 5:55The nice thing about this internal medullary lamina is that it’s actually a white matter
103. 6:00structure.
104. 6:01The second thing that’s really cool is that it separates the Thalamus into three different
105. 6:06groups.
106. 6:07The first one that we’re gonna talk about, is the anterior group of nuclei, within the
107. 6:10anterior tubercle.
108. 6:12Then we have the medial group of nuclei, and the lateral group of nuclei.
109. 6:16Alright, now the Thalamus is actually.
110. 6:19You know, when you learning about it it can be quite daunting.
111. 6:21Especially when you look in the books they got all these nuclei and you’re like ‘’What
112. 6:25the crap is going on?’’.
113. 6:26I’ll only focus on the very basic neuroanatomy of it so that you kinda have a good ground
114. 6:31base in understanding the Thalamus.
115. 6:33So let’s do the anterior nuclei first.
116. 6:36The anterior nuclei is a part of a circuit responsible for emotional episodic memory.
117. 6:42Now, what doe that mean?
118. 6:44That means, your ability to recall and mentally re-experience specific episodes from one’s
119. 6:50personal past.
120. 6:51So this is the one that keeps you awake at night when you’re brain goes wandering off
121. 6:54about awkward situations you’ve been in.
122. 6:57And it can do that because it’s a part of what is called the Limbic System.
123. 7:01We’ll talk about the limbic system in detail when we go through the internal structures
124. 7:05of the hemispheres, but the Limbic system is initially responsible for the control of
125. 7:09emotions, behaviors, motivation, and memory.
126. 7:13And it’s a system that consists of several parts.
127. 7:16And the ones that are involved with the anterior group of nuclei are, you know, the Thalamus
128. 7:21itself, the Hypothalamus.
129. 7:23The Amygdala, Hypocampus, the cingulate gyrus, and the fornix.
130. 7:27So all of these structures are involved with the anterior nuclei of the Thalamus.
131. 7:32Let’s see how.
132. 7:33So the Mamillary body, which is a part of the Hypothalamus.
133. 7:36Send fibers to our anterior thalamic nuclei.
134. 7:40From the anterior thalamic nuclei, they send their axons to the cingulate gyrus.
135. 7:45The cingulate gyrus then sends axons downwards, and they eventually reach the Hippocampus.
136. 7:50Then, from the hippocampus, fibers go through the fornix and then finish the circuit in
137. 7:55the mamilly body again.
138. 7:57This whole circuit is called the papez circuit.
139. 8:00And this is the circuit that give you the ability to recall and reexperience past memory,
140. 8:05for emotional episodic memory.
141. 8:08Next, we have the medial group nuclei.
142. 8:12Or also called the medial dorsal nuclei.
143. 8:15And what these nuclei do is that they relate the sensory input, motor input, and olfactory
144. 8:21input with emotions.
145. 8:23Meaning gives you the emotional aspect of smell or any sensory or motor input.
146. 8:28And it’s able to do that because it receives its fibers from the olfactory Cortex, which
147. 8:33is the area that perceives smell.
148. 8:36It also receives input from the Amygdala, which is involved in fear, anxiety, aggression,
149. 8:41and all of those kind of emotions.
150. 8:43So it will send its input to the medial dorsal nucleus.
151. 8:46And then there’s the Hypothalamus.
152. 8:48So all of these send their axons to the lateral thalamic nucleus.
153. 8:53And once the medial dorsal nucleus receives all the emotions, it sends that information
154. 8:58to the prefrontal cortex, which is an area responsible for attention, personality, abstract
155. 9:03thinking, and all of those things.
156. 9:05Cool, so that’s the medial dorsal nucleus.
157. 9:09Now let’s do the lateral group of nuclei The Lateral group of nuclei is divided into
158. 9:14a lateral Dorsal row, and a lateral Ventral row.
159. 9:18And all the way on the back here, we have our Pulvinar.
160. 9:21The lateral Dorsal row is divided into two portions.
161. 9:24It’s divided into the Lateral Dorsal nuclei, and the Lateral Posterior nuclei.
162. 9:30The Lateral dorsal, lateral posterior and the pulvinar are mostly involved in visual
163. 9:35and auditory senses, I’ll show you in a bit when we talk about the medial geniculate
164. 9:39body and the lateral geniculate body, so we’ll put these on hold a little bit.
165. 9:43So let’s talk about the Lateral Ventral row.
166. 9:46This is actually the most important part of the Thalamus.
167. 9:49And it consist of the ventral Anterior and the ventral Lateral.
168. 9:52These two nuclei are a part of the basal ganglia.
169. 9:56Remember the basal ganglia are also subcortical grey matter, but they’re responsible for
170. 10:02coordinating, starting and stopping voluntary movements.
171. 10:05They include the Caudate nucleus, Putamen, Globus pallidus exterus, and internus.
172. 10:11Thalamus, but not the whole Thalamus.
173. 10:13Only the ventral anterior and the ventral lateral group of nuclei are gonna be a part
174. 10:17of the basal ganglia.
175. 10:19That is why they’re special.
176. 10:20The last ones are the subthalamic nuclei and the substantia nigra of the Midbrain.
177. 10:25So if we take all the structures of the basal ganglia and group them all together.
178. 10:30We’ll see that the Ventral anterior and the ventral lateral nuclei are also going
179. 10:35to be responsible for initiation and planning of movement.
180. 10:39And it does that by the Basal ganglia structures receiving impulses from the primary motor
181. 10:44cortex.
182. 10:45Impulses within the basal ganglion are going to go through the ventral anterior and the
183. 10:50ventral lateral nuclei, which are then going to end up back towards the primary motor cortex,
184. 10:55for a better planning and initiation of the movement
185. 10:58Another thing that is kinda special for the ventral lateral, in addition to the basal
186. 11:02ganglia is, you know the cerebellum?
187. 11:05The cerebellum is involved in receiving information about proprioception.
188. 11:10Meaning it receives information about the position of your muscles your tendons, you
189. 11:13joints, your ligaments.
190. 11:15It’s receiving all of that information through the spinocerebellar tract and the external
191. 11:20arcuate fibers.
192. 11:22It also receives information from the inner ear.
193. 11:24You know the vestibular system?
194. 11:26Which is involved in balance?
195. 11:27The cerebellum receives information from the inner ear through the vestibulocerebellar
196. 11:32tract, based upon our equilibrium.
197. 11:35It also receives a pre-planned motor plan, through the corticopontocerebellar tract,
198. 11:41which remember either goes to the red nucleus and then down as the rubrospinal tract, or
199. 11:46it ascends back up through the Thalamus, or specifically the ventral lateral nucleus.
200. 11:52SO the cerebellum receives all of that information.
201. 11:54Our balance, or proprioception, the motor plan and all of those things.
202. 11:59And then it sends it to the Thalamus and then the signals are sent up to the Cortex.
203. 12:04What area of the cerebral Cortex you say?
204. 12:06The primary motor cortex.
205. 12:08This is a very cool and controlled process.
206. 12:10All of this just to move a finger or a limb.
207. 12:13The last two nuclei are the ventro-posterio-Lateral nucleus, or abbreviated as VPL.
208. 12:19It receives sensory information for the Trunk and Limb, through a tract that you’re probably
209. 12:24familiar with by now.
210. 12:26That tract originates from the Gracile fascicle and the Cuneate Fascicle.
211. 12:30They are responsible for epicritic sensibility, proprioception, and mechanoreceptors like
212. 12:35touch and vibration.
213. 12:37They will ascend as the medial lemniscus and then go to the VPL nucleus to be directed
214. 12:42towards the primary somatosensory Cortex.
215. 12:45Another tract it receives input from is the spinothalamic tract.
216. 12:49And remember this tract is responsible for sensation in regards to Pain, Temperature,
217. 12:54Pressure, and Touch.
218. 12:56The spinothalamic tract goes to the VTL, and then up to the somatosensory Cortex.
219. 13:01So that is the ventroposteriolateral nuclei.
220. 13:05The other nucleus is the ventroposteriomedial nucleus.
221. 13:09Or abbreviated as the VPM.
222. 13:11These nuclei are also sensory nuclei, and they receive sensory information from the
223. 13:16Face, as well as Gustation, or sense of taste.
224. 13:20It receives its senses from the Trigeminal nerve, through the trigeminal lemniscus about
225. 13:25proprioception, pain, touch, all of those things in the facial region.
226. 13:30So that is this one.
227. 13:31The other one is Gustation, or taste.
228. 13:34You know there are specific cranial nerves responsible for the sense of taste.
229. 13:39These are the facial, glossopharyngeal, and the vagus nerve.
230. 13:42All of them will go the VPM.
231. 13:44And then from the VentroPosterioMedial Nuclei, They will give off axons towards the…
232. 13:51Primary sensory cortex.
233. 13:52Awesome.
234. 13:53Now we’re done with the Thalamus.
235. 13:56From this view.
236. 13:57We can talk about the metathalamus.
237. 13:59Which remember are the Medial geniculate body, and the Lateral geniculate body.
238. 14:03The Medial Geniculate body is associated with hearing.
239. 14:07So it’s a part of the…
240. 14:08Auditory Pathway.
241. 14:10This pathway starts around the cochlea of the inner ear, which converts hearing into
242. 14:14nerve signals through the hair cells.
243. 14:17From here, these nerve signals are sent through the cochlear nerve to the.. cochlear nuclei
244. 14:23in Pons.
245. 14:24The cochlear nuclei will then cross to the other side and form the trapezoid body of
246. 14:29pons, and then ascend as the lateral lemniscus, to the inferior colliculi.
247. 14:35Then through the brachium of the inferior coliculus, the axons will reach the medial
248. 14:40geniculate body, and then reach the primary auditory Cortex, which is located at the superior
249. 14:45temporal gyrus.
250. 14:47So that is the Medial Geniculate Body.
251. 14:50The lateral geniculate body is related to vision.
252. 14:53So it’s associated with the visual pathway.
253. 14:55So remember, Within the retina of your eyes, you have receptors for the 2nd cranial nerve,
254. 15:00the optic nerve.
255. 15:01The fibers of the optic nerve will go back, and then half of the fibers will cross and
256. 15:07form the optic chiasm.
257. 15:09After that, they will synapse with the Lateral geniculate bodies, and From the Lateral Geniculate
258. 15:14bodies, the fibers will go back to the occipital lobe, which is where you’ll find the primary
259. 15:19visual Cortex.
260. 15:20When they go to the Cortex, that is when you’re consciously aware of the things you see around
261. 15:27you.
262. 15:28But fibers also go from the lateral geniculate bodies to the superior colliculi through the
263. 15:33Brachium of the superior colliculi.
264. 15:36The superior colliculi are responsible for a coordinated movement of the eyes and neck,
265. 15:40and it’s able to do that through the tectospinal tract, which sends motor impulses for the
266. 15:46eyes and the neck muscles.
267. 15:48So the superior and the inferior colliculus is responsible for Reflexive movement of the
268. 15:53head and neck through visual and hearing stimulus.
269. 15:57Now.
270. 15:58Remember we talked about the pulvinar and the lateral posterior and the lateral dorsal
271. 16:02nucleus?
272. 16:03They’re actually involved in all of these things.
273. 16:06But the Pulvinar especially, will receive fibers from the medial geniculate body about
274. 16:11hearing, Lateral geniculate body about vision, as well as superior colliculus for reflexive
275. 16:16movement of the head through visual stimulus, and inferior colliculus for reflexive movement
276. 16:21of the head through auditory stimulus.
277. 16:24All of those go-to Pulvinar, and the pulvinar sends the information primarily to the tertiary
278. 16:30areas in the brain, which gives you the possibility to take past experiences, let’s say someone's
279. 16:35face, or maybe even a flower or a facial expression.
280. 16:39And it helps with recognition.
281. 16:40It gives meaning to the image you’re seeing.
282. 16:43That is what the Pulvinar is responsible for.
283. 16:45Talking all of that information and sending them to the association areas, or the tertiary
284. 16:51and secondary areas of the brain.
285. 16:53So that was the metathalamus, boom.
286. 16:55Let’s move on.
287. 16:57The next one on our list is the Epithalamus.
288. 17:00So let’s go back to this image.
289. 17:02We’re already familiar with the Thalamus now.
290. 17:05But on the posterior side, we can see the Epithalamus right here.
291. 17:09The Epithalamus is a veery small area, and it consists of mainly the pineal gland.
292. 17:15And the pineal gland mainly produces one of the most important hormones in our body, and
293. 17:21that is the hormone that makes u sleep, called melatonin.
294. 17:24So essentially, it regulates the sleep-wake cycle.
295. 17:28The Pineal gland is attached to the posterior part of the Thalamus.
296. 17:32On either side of the pineal gland, you’ll see a triangular-like structure called the
297. 17:37Habenular Trigone, which is white matter that contains some habenular nuclei which are considered
298. 17:42to be a part of the limbic system.
299. 17:44Between the habenular triangle, we’ll find the habenular commissure, which connects both
300. 17:49habenular trigones together.
301. 17:52And you’ll also find the posterior commissure here as well.
302. 17:55So that is the Epithalamus.
303. 17:57Next, let’s do the Subthalamus.
304. 17:59They’re called Sub-thalamus, so under the Thalamus.
305. 18:03So here is the Thalamus.
306. 18:04Here is the Subthalamus.
307. 18:06Or the subthalamic Nuclei.
308. 18:07And the Subthalamus is essentially a part of the basal ganglion.
309. 18:11SO all the other structures of the basal ganglion will work together with the Subthalamus to
310. 18:17help start a movement, stop movement and coordinate voluntary movement.
311. 18:22So that is all I had for the anatomy of the Subthalamus.
312. 18:25Let’s now do the last part of the diencephalon, which is the structure you’ll find around
313. 18:29the anterior portion of the third Ventricle, called the Hypothalamus.
314. 18:34Really what I want you more to understand rather than going detailed into the neuroanatomy
315. 18:38is to know that the Hypothalamus is more of an area that is made up of different parts.
316. 18:44Or different nuclei.
317. 18:45And it has some external parts that are considered a part of the Hypothalamus.
318. 18:50Remember the optic pathway has the optic chiasm and the optic tracts.
319. 18:55Both of these are consideres a part of the Hypothalamus.
320. 18:58As mentioned earlier, some sources mention these as a separate part of Diencephalon as
321. 19:02Thalamus Opticus, but here we’ll include them as a part of the Hypothalamus.
322. 19:07So, if you look at the Diencephalon, from an anterior perspective, we’ll see the Hypothalamus
323. 19:12here in red, and the Optic chiasm and the optic tract right here.
324. 19:17Awesome.
325. 19:18Now, the other part of the Hypothalamus is going to be the Mammillary body.
326. 19:22And they’re responsible for Emotional Episodic memory as mentioned earlier.
327. 19:26As well as reflexes associated with olfaction.
328. 19:29Remember earlier when we went through the papez circuit associated with the anterior
329. 19:33nuclei of the Thalamus?
330. 19:35Where do we have the Thalamus, Hypothalamus, Amygdala, Hippocampus, cingulate gyrus, and
331. 19:40fornix?
332. 19:41The mammillary body will send axons to the anterior nuclei of the Thalamus.
333. 19:46Which will send its fibers to the cingulate gyrus, and then to the hippocampal area, then
334. 19:51to the fornix, and back to the mammillary body.
335. 19:53This circuit will be responsible for emotional episodic memory, which is the emotional reaction
336. 19:59to a past memory.
337. 20:01So that was the mamillary bodies.
338. 20:04Other things we’ll find in the Hypothalamus are these Hypothalamic nuclei.
339. 20:08There are many nuclei in the Hypothalamus.
340. 20:11Some of them send down their axons through the tuber cinerum, which will get tighter
341. 20:16and form a stalk called the infundibulum, which will then synapse with nuclei in the
342. 20:21posterior pituitary gland.
343. 20:23So hormones released from the posterior pituitary gland, like vasopressin or Oxytocin, get their
344. 20:29trigger stimulus from the Hypothalamus through these fibers.
345. 20:33Those are the major structures of the Hypothalamus.
346. 20:36If you wanna go deeper into the neurology of it.
347. 20:39We can look at a side view of the Hypothalamus and really look at all the hypothalamic nuclei.
348. 20:43They’re arranged into areas.
349. 20:46Like the lateral hypothalamic area, the posterior hypothalamic area, and the anterior hypothalamic
350. 20:51area.
351. 20:52These nuclei are responsible for different things.
352. 20:55The paraventricular nuclei are associated with pain for example.
353. 20:59The preoptic nucleus decreases the heart rate and the blood pressure and many other things.
354. 21:04We got the Suprachiasmatic nucleus which is a part of the circadian rhythm, the sleep-wake
355. 21:09cycle, Supraoptic nucleus for thirst, Arcuate nucleus which regulates the release of many
356. 21:15hormones.
357. 21:16The ventromedial nucleus for the satiety feeling, this nucleus doesn’t work in my body.
358. 21:21I’m always hungry.
359. 21:22Then we got our mammillary body here.
360. 21:24The dorsomedial nucleus for sleep regulation and food intake.
361. 21:28You might wanna go into detail into this when you study the physiology or neurology.
362. 21:33But for now.
363. 21:34That was the anatomy of the Diencephalon and I hope that was helpful.
364. 21:35Please put a like, comment, share, whatever you find convenient to you.
365. 21:36Our next video will be about the Telencephalon.