| 00:02 | So this is lecture four of And we're continuing talking about neurons and |
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| 00:09 | talked about several important things about Last lecture, we discussed a little |
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| 00:16 | about the genes, genetic expression as may find it as it differs in |
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| 00:22 | brains versus neurologically impaired brains. The that you use the gene micro |
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| 00:28 | we talked about the organelles and we about the fluid mosaic model of the |
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| 00:33 | membrane. So I encourage you to on that link for the video. |
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| 00:37 | about a two minute video to watch then we spent quite a bit of |
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| 00:41 | talking about sino skeletal elements, how really important, how they support the |
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| 00:45 | structure of the South, also the boundaries of the cell. So if |
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| 00:50 | is a reshaping physical reshaping of the of the dendritic spines, you'll also |
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| 00:56 | the structuring of the underlying cyto skeletal to allow for the membranes to reshape |
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| 01:03 | support new shape that they may produce their processes. So, the cytoskeleton |
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| 01:09 | also are contributing to axonal transport. particular microtubules and microtubule highways. We |
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| 01:18 | about how you can use dyes and to take advantage of either anterograde or |
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| 01:26 | this case, retrograde transport from the into the cmas of neurons. And |
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| 01:31 | types of techniques allow us to visualize well the connectivity between the networks or |
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| 01:39 | in the periphery dispatch might be connected a specific network of neurons. And |
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| 01:45 | we ventured into introducing our first uh neurological disorder that we spent quite a |
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| 01:52 | of time talking about. Although we spoke about epilepsy and status epilepticus, |
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| 01:57 | particular, in Fin gauge, who traumatic brain injury. And as a |
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| 02:02 | , developed epilepsy as comorbidity and passed epilepsy. 10 years later, 12 |
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| 02:09 | later, passed from status epilepticus, is a major generalized seizure. Uh |
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| 02:15 | epilepsy patients would have in the last we spoke about Alzheimer's disease and we |
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| 02:21 | the cellular pathology hallmarks of Alzheimer's We talked about formation of beta amyloid |
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| 02:29 | extracellularly, but as they form they actually start impinging on the territory |
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| 02:38 | neurons and start compromising in particular axons Axion initial segments, compromising the production |
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| 02:46 | action potentials and also the communication between interconnected cells uh and neurofibrillary tangles that |
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| 02:56 | due to the tau protein over expression uh aggregation inside the cells around the |
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| 03:05 | and around neurofibril and microtubules causing impairment external transport in intercellular. And in |
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| 03:15 | to the cellular pathology, we also at what happens when this disease progresses |
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| 03:24 | blonde stages and when a person has Alzheimer's disease. There's significant loss of |
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| 03:32 | , uh gray brain matter, in shrinkage of the brain. We talked |
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| 03:39 | the onset of the disease typically at age of 55. Uh plus the |
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| 03:47 | and progression of the symptomology. The that it is a terminal disease without |
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| 03:53 | and that epilepsy is a common comorbidity patients that have Alzheimer's disease. So |
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| 04:03 | we're moving on to dendrites and we're to talk about dendritic anatomy. We |
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| 04:09 | spoke how dendrites have. Uh the like petal cells would have. This |
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| 04:22 | an apical dendrite because it's at the . It also has basal dendrites because |
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| 04:29 | at the base. And these excitatory will also have the axon that we'll |
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| 04:34 | about in a second. And this a parameter cell. This is a |
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| 04:38 | petal neuron because it selma has a pyramid like shape. Uh and of |
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| 04:46 | apical dendrites, if we look at anatomy of these dendrites, a lot |
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| 04:50 | these dendrites will contain spines, but are also a spiny or smooth |
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| 04:55 | So, not all neurons that have and these projections, massive dendritic |
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| 05:02 | we'll have them to respond and some them will be smooth. Ok. |
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| 05:11 | , there is a lot of differences neuronal morphology and it's not just the |
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| 05:17 | cells. This is an example of petal self. This is an example |
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| 05:22 | a stellate cell. So there are subtypes of cells morphologically and functionally that |
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| 05:28 | have dendritic spines or in some instances not have dendritic spines. And we |
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| 05:33 | talk about these morphological differences in the in subtyping, different cell subtypes. |
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| 05:40 | , dendritic spines in general, as mentioned are the most malleable, the |
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| 05:46 | plastic units of the south, some like the leaves on the tree |
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| 05:52 | So every season the branches will stay , but the leaves will drop and |
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| 05:58 | leaves will regrow. So during early , we actually have a lot of |
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| 06:04 | that are interconnected throughout the whole brain nonspecifically. Then we have a lot |
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| 06:10 | synopsis and a lot of dendritic spines in adulthood, we have a lesser |
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| 06:16 | of these synapses and lesser number of spines and more precise connectivity between different |
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| 06:25 | and neuronal networks. And this process development and refinement is referred to as |
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| 06:32 | process of synaptic plasticity. So during process of synoptic plasticity, the active |
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| 06:39 | , the ones that have pre synoptic right here, recall these red round |
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| 06:47 | of vasic that will contain neurotransmitter. juxtaposed to these psyop terminals. So |
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| 06:54 | you have very active synapse, that may become large in size and may |
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| 07:00 | increase even larger in size and the this dendritic spine becomes, it can |
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| 07:07 | 123 po synoptic densities filled with the that and and and by that |
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| 07:14 | it becomes very efficient, very effective the stimulation pre synoptic vesicular release from |
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| 07:22 | side will always result in the response the posy tic dendritic spine because it's |
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| 07:27 | large spine. And so the largest and the more active spines will contain |
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| 07:35 | densities, larger numbers of fossil optic uh receptors and therefore, will have |
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| 07:41 | responses. The active spines, the that active synopsis and the activated spines |
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| 07:48 | the ones that strengthen and establish The synopsis that become less active, |
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| 07:54 | may shrink in size and eventually be all completely get pruned. We call |
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| 08:03 | like little leaves on the tree that get pruned and they disappear. And |
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| 08:07 | because of the lack of activity or of activity between specific pre synoptic terminals |
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| 08:15 | plus synoptic densities. So, spines malleable spine numbers, anatomy and |
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| 08:23 | Distribution of the spines on the basal optical uh uh uh at the bottom |
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| 08:30 | the optical dendrite versus at the apex the apical dendrite or the top of |
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| 08:36 | , you'll have different densities of these spines. They're controlled by activity and |
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| 08:42 | genes. So there are certain genes certain proteins that patrol and monitor the |
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| 08:48 | expression during the development, correct expression the number, the shapes and the |
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| 08:55 | of these dendritic spines. These dendritic also contains synaptic polar ribosomes, spin |
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| 09:04 | , smooth endoplasmic reticulum, uh mitochondria makes the spine somewhat biochemically independent from |
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| 09:14 | rest of the dendrite and the rest the SOMA that means that they're capable |
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| 09:19 | some post translational modifications with these polar soal complexes. And they have energy |
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| 09:26 | with a TP to bio synthesize and care of some things locally without involving |
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| 09:35 | SOMA. A activity will control how synopses form where they form and activity |
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| 09:47 | what's going to determine if they strengthen sy synopsis or they weaken. |
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| 09:56 | So we talked about cyto skeletal elements atonal transport and Alzheimer's disease. And |
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| 10:01 | we talk about dendritic spines, it's to note that if there is abnormal |
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| 10:08 | of dendritic spines, there can be mental uh disability that forms an intellectual |
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| 10:18 | that forms in individuals that have certain that caused to the abnormal formation and |
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| 10:26 | of these genetic spines, abnormal shape these spines. So, this condition |
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| 10:30 | called fragile X. It's actually a protein due to a single gene |
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| 10:38 | um loss, it's tied with X and X chromosome becomes fragile. |
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| 10:45 | males are more affected by fragile X . It's an intellectual disability with certain |
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| 10:55 | features. Ok. And that's something is worth thinking about. Can you |
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| 11:05 | by looking at a person if they Alzheimer's or not? Right? Probably |
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| 11:16 | . Uh In some instances, you recognize a person has a bodily deformity |
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| 11:25 | . And you can actually correlate it some additional information to specific neurological |
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| 11:32 | And in the case of fragile Children with fragile acts will have elongated |
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| 11:39 | and quite large es and somebody will , hey, that's, that's |
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| 11:44 | You know, I have long face , and long es and large |
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| 11:48 | It's like, I don't, I have this condition. So it's also |
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| 11:51 | a, you know, not something a doctor would see a child at |
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| 11:56 | . I just see it's that fragile acts, you cannot do |
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| 12:00 | You still have to have medical you still have to look at other |
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| 12:04 | symptomology and quite often um these kids also have epilepsy and seizures too. |
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| 12:14 | this disorder is autism spectrum disorder. quite often autism is a comorbid and |
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| 12:22 | fragile legs too, which is a bit more complex. That whole umbrella |
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| 12:27 | autism spectrum disorders. It's a lot intellectual mental as well as behavioral disabilities |
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| 12:35 | get grouped under that umbrella. So a while, uh Fragile X was |
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| 12:40 | to be under the umbrella of autism disorders, but it now is being |
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| 12:46 | uh uh uh A SDS comorbidity to X. Now imagine if you have |
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| 12:54 | under spine anatomy, what happens to cell. So this is an example |
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| 13:00 | the neuron everywhere where you're seeing green , the green punk ta these are |
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| 13:07 | receptors. Glue R stands for glutamate . So everywhere where you see this |
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| 13:14 | dots right here are excitatory synopsis and shows that this particular neuron, I |
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| 13:22 | know you can count all the Some of them overlap but probably has |
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| 13:25 | of excitatory synopsis on it. Uh you're seeing these other punctate and orange |
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| 13:33 | these orange pate are stains for Gaba . So everywhere where you're seeing orange |
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| 13:42 | , you have inhibitory synapses gamma receptors be associated with the inhibitor synopsis. |
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| 13:50 | you can see how many of these and inhibitory synapses. Thousands of them |
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| 13:55 | hundreds of them are formed on a drum. Some neurons will have thousands |
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| 14:02 | inputs. Other neurons can have hundreds thousands of inputs. You can see |
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| 14:09 | most of the synopsis are being formed the dendrites and also around the |
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| 14:16 | So what happens if you have impaired lyric spine? You have abnormal |
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| 14:23 | presynaptic post synaptic side. Uh This has to process all of the excitatory |
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| 14:31 | . Sometimes it can receive hundreds of inputs. At the same time as |
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| 14:35 | receiving hundreds of inhibitory inputs in different of the cell and very fast within |
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| 14:41 | few milliseconds, the cell has to all of these hundreds of inputs and |
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| 14:47 | a decision to fire or not to . That is the question to fire |
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| 14:52 | action potential to produce an action potential not. And if you have impaired |
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| 14:59 | and impaired synaptic transmission, abnormal dendritic , there will be a lot of |
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| 15:04 | lists in processing the information and integrating information. There's potentially going to be |
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| 15:11 | imbalance in the activity where excitation might uncontrolled or less controlled than in normal |
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| 15:20 | . Yes. So because you said um does that kind of help like |
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| 15:26 | the reason why um kids with autism have sensitivities towards sounds towards like |
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| 15:33 | Um Just because like they're processing Not, not precisely actually, but |
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| 15:41 | is, this is again, this because autism spectrum disorders are such a |
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| 15:47 | umbrella. Yeah. So these, Children would have like uh like I |
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| 15:54 | , they would have intellectual disability, may have seizures. Uh I |
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| 16:00 | in some instances, they could be happy and laugh a lot. So |
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| 16:04 | may have some behavioral expressions too. but sensitivity to senses, that's, |
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| 16:11 | not necessarily something that would correlate with spines, although that's a really interesting |
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| 16:17 | . Um and maybe some of that will get answered uh in lecture |
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| 16:28 | And that is when we talk about phenomenon called synesthesia and our, |
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| 16:35 | and our ability to integrate multiple senses . And what happens if you lose |
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| 16:41 | sense, for example. And in , what's interesting in the brain is |
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| 16:48 | it's finite structure that can learn. a lot of times if one sense |
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| 16:53 | impaired, the other one takes over becomes more enhanced. So everything is |
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| 17:00 | enhanced. If you lost uh lose hearing, maybe your vision and your |
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| 17:07 | of sensory information becomes more meaningful for . It's more enhanced and uh the |
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| 17:14 | has this plasticity into adulthood and what happen is sometimes the remaining normal neurons |
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| 17:22 | take over the areas of the brain have been damaged and that can |
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| 17:28 | help heighten that sense. And equally with autism spectrum disorders, Children, |
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| 17:35 | may have a lot of let's say uh struggles, um social interactions, |
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| 17:44 | may struggle with that too. They not score very well on the |
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| 17:51 | But I knew a person and it's uncommon in college who had uh who |
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| 17:59 | diagnosis with autism spectrum disorders. And knew every African president in every African |
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| 18:09 | for the entire 20th century. And also taught himself self taught himself, |
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| 18:16 | , which is the one of the difficult languages in the world to, |
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| 18:20 | learn, let alone to self teach , you know. So a lot |
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| 18:26 | times where it's missing in other it could get compensated and you actually |
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| 18:31 | have uh like savant, almost like in some instances. You just may |
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| 18:37 | have the ability to connect these senses place them within the same context and |
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| 18:43 | that everybody else does, you And that's why maybe your question was |
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| 18:47 | the heightened census. So, uh it does relate to a SD |
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| 18:53 | and we'll come back to it when talk about synesthesia. So once we |
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| 19:00 | neurons, we wanted to classify Ramonica Howell already started classifying neurons. |
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| 19:05 | the only way that you could classify was based on morphology. So this |
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| 19:09 | a unipolar cell, bipolar cell multipolar many poles, two poles north south |
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| 19:16 | of a one process that splits uh uh along the same plane as unipolar |
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| 19:24 | types of cells that are unipolar in neurons, bipolar cells are bipolar cells |
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| 19:30 | retina. And we look at a of bipolar cells. And the general |
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| 19:35 | we study the retinal circuit in the system lectures. Pseudo unipolar cell is |
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| 19:42 | dorsal ganglia cell. Remember I drew a table for you or I didn't |
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| 19:48 | a table for you yet. Oh haven't let me draw a table. |
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| 19:52 | what I like to do on this is I like to ask matching questions |
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| 19:58 | the major cell subtypes that we So for example, we're talking over |
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| 20:03 | about petal cells, right? So would put sal and I would make |
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| 20:12 | a little table for yourself and then would put Coram it all and there's |
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| 20:20 | questions and certain features of this petal questions for you. Certain features that |
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| 20:26 | may wanna put here. I'm gonna dorsal root ganglion cell because we talked |
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| 20:33 | dorsal root ganglion cell. We talked spinal cord and all of the sensory |
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| 20:38 | coming in dorsal root ganglion cell. we'll add another uh subtitle the sell |
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| 20:48 | . Uh let's say motor neuron. right. And what are some of |
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| 20:56 | things I may want to know? may want to know morphology of these |
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| 21:03 | and morphology and the parameter cells, already know that parameter cells are m |
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| 21:10 | . So if I asked you that , that would be like OK, |
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| 21:13 | multipolar easy. All of these are cells here. But you can see |
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| 21:19 | a significant difference in their structure, morphology. And I hope you appreciate |
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| 21:25 | fact that it's showing here, the cord motor neurons can have 10,000 plus |
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| 21:31 | synopsis. And the this pini cell the cerebellum has 100 50,000 C. |
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| 21:39 | , that's a whole lot of inputs are coming into this dendritic tree to |
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| 21:45 | processed by the cell integrated in the . So what is the morphology of |
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| 21:51 | cell that I may ask you, I ask you about whether it has |
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| 21:55 | versus basal dendrites or something like Ok. What about dorsal root ganglia |
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| 22:03 | ? Well, it's pseudo unipolar pseudo . What about motor neuron? |
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| 22:13 | it's multipolar because we are not discussing about its anatomy. Ok. Then |
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| 22:23 | this is just morphology of neurons, we're moving and trying to understand is |
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| 22:29 | alone enough to subtype all of the in the brain. And the answer |
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| 22:33 | no. So there are many different in which we classify different neuronal |
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| 22:39 | And this is a moving target because invent new technologies and new techniques in |
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| 22:43 | lab and new tools that allow us either change this gold standard of how |
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| 22:51 | we set out different neurons or move or improve it. But there are |
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| 22:57 | ways of doing that. First of , based on the connectivity, some |
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| 23:01 | the cells are projection cells and other are interneurons. What does it mean |
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| 23:06 | a cell to be a projection So here is one brain structure |
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| 23:14 | A and this is another brain structure . B OK. Projection cells like |
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| 23:23 | petal cell are typically excitatory cells. , because they're excitatory, they typically |
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| 23:32 | glutamate and their projection cells because they're to project that information and release glutamate |
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| 23:41 | neurotransmitter and the adjacent neuronal network. these are projection neurons and they're typically |
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| 23:49 | and they typically release neurotransmitters. So another good point to put on the |
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| 23:56 | neurotransmitter. What neurotransmitter is it? para cell is glutamate, you're gonna |
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| 24:04 | to fill in the blind here OK. It's easy. It will |
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| 24:08 | out in this course, but you know that it is acetylcholine and |
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| 24:13 | Now. So these are projection What are interneurons? Interneurons are the |
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| 24:20 | that be located and there are different of interneurons that are located in this |
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| 24:31 | here. And these interneurons, they connect to each other, they will |
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| 24:38 | to the parameter cells. However, axons are going to stay within this |
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| 24:46 | network. So their axons, their are going to stay within this local |
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| 24:55 | . They're typically inhibitory and they typically Gaba. So here is another good |
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| 25:03 | to put here to continue the list line and you can put into |
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| 25:10 | for example, everybody can see So these are interneurons. So they |
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| 25:21 | not projecting out of this network. rather control activity locally in this |
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| 25:28 | They're predominantly inhibitory and they control the , the types of activity, the |
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| 25:34 | , the amount of activity that these excitatory cells are going to communicate to |
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| 25:39 | adjacent networks. Ok. So this what we call excited buildings. Cells |
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| 25:47 | contain glutamate and release glutamate inhibitory cells contain Gaba and release Gaba inhibitory cells |
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| 25:58 | have to be distinguished from one another on cells, specific markers that we'll |
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| 26:03 | in a second. These cells, I mentioned, they're not only unique |
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| 26:09 | and projection wise, whether the local or projection cells, they also have |
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| 26:15 | distinct neurotransmitters, glutamate Gaba. And also learn about some of these cells |
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| 26:21 | neuropeptides. And we'll also study monoamine . We'll study uh signaling by dopamine |
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| 26:31 | and serotonin cells and acetylcholine cells. those are also considered as neurotransmitters. |
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| 26:38 | later, you will be able to more cells to the stable activity |
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| 26:45 | So what Ramona Cajal didn't know is he suggested is that neurons communicate to |
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| 26:51 | other through a particular pattern. All comes into dendrites, thermal processes, |
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| 26:56 | sends the signal. But what he know that individual neurons can produce action |
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| 27:02 | and So in the late thirties and later during World War two, when |
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| 27:06 | was a lot of uh military equipment by allies by Brits and Americans, |
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| 27:15 | for the Navy and submarines. They developing really fast circuits and fast circuits |
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| 27:22 | were also oscilloscopes and those fast electrical and connections and fact that electrics Theology |
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| 27:30 | to this date, we have B C cables, which stands for British |
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| 27:35 | Cable and those BNC cables interconnect our , the amplifiers uh and oscilloscopes, |
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| 27:42 | they're uh or these days, it's oscilloscopes actually. But we still use |
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| 27:48 | cables for recording electrical activity in And in 1939 Hodgkin and Huxley published |
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| 27:55 | first in intercellular recording of that action and they show that neurons are capable |
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| 28:02 | one to few milliseconds had a change their membrane potential from about minus 70 |
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| 28:09 | to approximately plus 30 plus 40 So they're capable of producing these very |
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| 28:16 | electrical sparks of activity. And that's that was not possible to pick up |
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| 28:21 | they're so fast. They're just one , one millisecond. How many milliseconds |
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| 28:27 | ? In a second? It's 1000 in a second. So you have |
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| 28:32 | have really fast circuits to pick up activity. And from that point |
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| 28:37 | it becomes very important that we start the action potential, firing patterns or |
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| 28:45 | signatures. It's called firing just because , it's a very fast event. |
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| 28:50 | referred to as action potential spike or activity of a neuron. Now, |
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| 28:58 | it became very important to understand whether that look different morphologically, whether they |
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| 29:05 | different action potentials, the same action , or whether the different patterns of |
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| 29:10 | action potentials would be indeed may be same are the same for the most |
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| 29:15 | . But the patterns are different than subtypes of cells. Finally, with |
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| 29:20 | age of genetics, we understood that cell subtypes express different subsets of |
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| 29:28 | So all cells in the brain and the body all have the same |
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| 29:34 | the same DNA code. And what one subtype of a cell different from |
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| 29:39 | is that it's not all the same from one code that get expressed in |
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| 29:44 | certain subtype of cell. So there's subsets of genes that considerable overlap. |
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| 29:50 | course of many genes that 30,000 genes the brain or so, there's gonna |
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| 29:55 | significant overlap in tens of thousands of overlapping between potentially two cells. But |
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| 30:01 | also gonna be differences in the expression these genes which leads to different subsets |
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| 30:08 | proteins, receptors, expression of different and other molecules that we refer to |
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| 30:15 | cells specific markers. Yeah. So this example, we're now using the |
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| 30:24 | that we acquired in the scores. is infrared microscopy. So remember you |
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| 30:30 | use infrared uh microscopy, infrared cameras visualize neurons. These are micro |
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| 30:39 | So neurons are about 10 micrometers in micro electrodes, about one micrometer at |
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| 30:44 | tip in diameter. Those micro electrodes record activity from individual neurons. Sometimes |
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| 30:52 | will hear intracellular recordings. Sometimes you hear patch clamp, patch clamp |
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| 31:00 | And if you are around electrophysiologist, will say I'm going patching for a |
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| 31:05 | of hours. So that's what that that they're going to sit at a |
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| 31:13 | . OK. This is an electrophysiology . OK. This is only a |
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| 31:19 | small portion of it. This is microscope and four electrodes and the tissue |
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| 31:25 | here that you visualize through infra And you're not seeing about 10 different |
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| 31:30 | of equipment connected to this, the , pre amplifiers, computers, audio |
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| 31:39 | , all of these things running at same time, the brain slide sitting |
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| 31:44 | here is being super fused with artificially cerebrospinal fluid. And well, it's |
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| 31:54 | artificial through the spinal. It's a oxygenation, but the slice thinks it's |
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| 32:00 | inside the brain and happy. So the neurons get approached by these micro |
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| 32:06 | , they, they for the most , they're really viable and and alive |
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| 32:11 | you can sustain this kind of recordings hours. But after a couple of |
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| 32:15 | of patching, you need to take break. Uh It's challenging technically and |
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| 32:21 | really monitoring about 20 different variables while trying to uh play a very kind |
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| 32:29 | a sophisticated video game uh between your and very complex micro manipulators and what |
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| 32:36 | seeing in the screen and what you're on the tracer. So it takes |
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| 32:41 | lot of multitasking. But so uh have this patching and in this |
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| 32:47 | I patched on to two cells and electrodes gave the same input, the |
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| 32:53 | stimulus to these two cells. And two cells look differently to me. |
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| 32:58 | cell must look differently. So I expecting a different response from them. |
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| 33:03 | cell on the left responds as you the stimulus. The cell on the |
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| 33:08 | responds with a very fast pattern of potentials. So we go like nonstop |
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| 33:17 | cell on the right, it receives same stimulus, the same inputs, |
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| 33:20 | same strength. But it responds with slower frequency of action potentials that is |
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| 33:29 | not sustained in frequency. So it faster and then it slows down. |
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| 33:38 | is what I call dialect of the . So action potential is the language |
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| 33:45 | these two cells speak different dialect of language. One is really fast, |
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| 33:51 | have actually dialects that are really fast one is really much slower and you |
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| 33:56 | dialects that are also much slower that . So this was a clue that |
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| 34:00 | are two cells that are different the different functional. And as far |
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| 34:08 | the pattern of the action potentials. that this pattern of the action potentials |
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| 34:14 | determine the pattern of neurotransmitter release. , will determine the pattern of activity |
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| 34:19 | goes into the adjacent networks. So that pattern of action potential is |
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| 34:24 | fast on will travel through one Another cell may have much slower |
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| 34:29 | And during the recording inside this microelectrode this type pad, we have a |
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| 34:37 | . This dye is called neuro also sometimes called biocyte. So this |
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| 34:43 | biotin dye, it gets placed inside cells during the recording. Then we |
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| 34:54 | the slice from underneath the microscope and do immuno histochemistry, histochemistry. In |
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| 35:02 | to reveal the seismology of these This is not Golgi stain. This |
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| 35:07 | a dye that enters inside the cell you have the cells hatched. So |
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| 35:14 | only the cells that you're reported from going to be filled with this dye |
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| 35:19 | just like ramonica hall. But 100 later, I reconstructed these cells instead |
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| 35:25 | us using camera lucida by hand, it did start, I still had |
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| 35:30 | chance to use camera Lucida switched to lucid which was uh done with uh |
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| 35:37 | a computer, use a cell So uh in black, you have |
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| 35:41 | dendrites and the dr trees and then it's an axon and this axon is |
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| 35:46 | out and it's actually it's going this . And then if I lost |
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| 35:50 | it got cut off in the OK. So then I was pretty |
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| 35:54 | that I reported from two different sub of cells that they are different |
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| 36:00 | they're different functionally And in addition, the experiment, we also cross stain |
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| 36:07 | cells with cells specific markers. So this case, we would use immuno |
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| 36:11 | chemistry and antibodies that attack visible markers as fluorescent markers. And it will |
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| 36:18 | you that certain cells express per This is a cell neuro reported from |
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| 36:23 | cell that had some matin and also diet Neurosin together in it. And |
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| 36:30 | tells us something about cells specific markers the cells and that's important uh now |
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| 36:39 | a little bit later in the last years or so, maybe longer. |
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| 36:45 | technique. Instead of putting the dot can also suction out the cytoplasm and |
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| 36:51 | study the messenger's RN AM RN So you can study the tran transcriptome |
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| 36:59 | individual neurons and correlate their molecular profiles their functional action potential firing signatures, |
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| 37:10 | location and specific networks and their precise . And all of these things are |
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| 37:16 | in order to determine what subtype of cell you're recording from. This is |
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| 37:22 | patch of a cortex and all of cells were targeted with the same stimulus |
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| 37:29 | micro electrodes. And you can see there is a diversity in the functional |
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| 37:36 | of these cells. So some of cells will again, not be |
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| 37:40 | fast firing trays, like others will bursting like the others are stuttering, |
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| 37:56 | and so on and so forth. these are all different neuronal dialects. |
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| 38:01 | you didn't know I'm really good at . Yeah, I can, I |
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| 38:06 | pretty much do any sub type. , it takes some practice, you |
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| 38:12 | , I, I recorded a TED in 2015 and I said action |
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| 38:17 | So I was walking by and you convert them into audio signal, electrical |
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| 38:22 | and it sounded like, almost like flap, like a tech. |
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| 38:28 | you know, it's like what's going and that's the action potential. So |
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| 38:32 | can actually listen to them. And you listen long enough, then you |
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| 38:37 | speaking their language to. All So uh why would you wanna uh |
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| 38:44 | that? Why would you want to different subtypes of cells? Why would |
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| 38:48 | want to know what kind of patterns produce? Of course, you want |
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| 38:51 | understand how to communicate information between each . In my case, this was |
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| 38:56 | rig here. We're talking about oil . Usually this is my rig that |
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| 39:01 | had in George Mason University when I doing my second toast doc. And |
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| 39:06 | question that I had at the as I was looking in the structure |
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| 39:09 | the brain that we'll talk about in world that's called the hippocampus. And |
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| 39:13 | question that I had is what type cell or which subtype of cell in |
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| 39:20 | starts seizures. So I was really to understand and this model in vitro |
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| 39:30 | and a brain slice and a what cells are starting seizures pretty |
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| 39:40 | And we found that it was the cells that had abnormal synchrony and started |
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| 39:47 | in a particular model of epilepsy that were using. And nobody will believe |
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| 39:54 | . So, you know, I like a MD phd as my |
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| 39:58 | famous neurosurgeon, a mathematical computational And it took us almost two years |
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| 40:08 | convince the reviewers that that was the that it's unusual pattern that in certain |
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| 40:14 | of epilepsy, you'll have the inhibitory , these inhibitor into neurons start the |
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| 40:21 | and that's really counterintuitive because you think excited to yourself, it's excitation that |
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| 40:27 | this whole thing and we found that was inhibition. So it took us |
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| 40:30 | two years to convince the reviewers. I said, if you discover something |
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| 40:36 | a scientist, you have to publish , which is peer reviewed. And |
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| 40:42 | say you have five reviewers and four of five says I've never seen something |
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| 40:47 | this before. You know, some in the in the ring. One |
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| 40:52 | them says the other one is like data analysis is wrong or something like |
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| 40:56 | . It's really not like this or you stained the wrong cells, you |
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| 41:01 | , so there would be all sorts , you know, a lot of |
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| 41:04 | good uh reasonable questioning and critiques from reviewers. But believe me in |
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| 41:13 | if just like in almost anywhere and earth, any condition, any uh |
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| 41:21 | , there's gonna be five viewers, of them madly unreasonable, just like |
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| 41:25 | five people in the group, one them may think or do something unreasonable |
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| 41:29 | a certain situation or another. So that's, that's very difficult. |
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| 41:34 | now we published this paper a year , we had a meeting and a |
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| 41:41 | from uh um at the time it in Harvard University showing data from humans |
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| 41:48 | how inter neurons start seizures in human in living human brains. From his |
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| 41:55 | , different types of recordings from it's a clinical eeg recordings and, |
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| 42:00 | single cell implant recordings. But they that inter neurons are indeed capable of |
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| 42:06 | the network abnormally and starting the And that's when as a scientist, |
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| 42:11 | really gratified because it's, it's really to know what molecules do and what |
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| 42:17 | start seizures. And these reduced models the brain slice in vitro or even |
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| 42:24 | vivo and the whole animal. But animal is a rat or a mouse |
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| 42:30 | that's not quite human. But you equivalent of that activity, equivalence of |
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| 42:37 | same mechanism, cellular mechanisms of this that is found in humans in |
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| 42:45 | And that and that makes your work , really relevant and directly applicable to |
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| 42:52 | condition uh of epilepsy. So never up. And uh sometimes if your |
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| 43:00 | holder breaks, it's quite expensive, just grab a pen and a tape |
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| 43:05 | try to, you know, the two hours, try to repair uh |
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| 43:11 | recordings and go home, eat, , wake up, repeat, go |
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| 43:19 | eat, shower, repeat, 8 12 hours every day until you get |
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| 43:25 | enough of the result. It's called sample size where you can see statistical |
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| 43:33 | in morphology in functional output in their as well as in whatever phenomenon you |
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| 43:40 | presenting in my case was which cell seizures. All right. So this |
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| 43:47 | a picture of hippocampus and it's a picture of the campus. It's really |
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| 43:53 | diagram. Hippocampus is mostly a three layer structure, stratum or the atom |
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| 44:01 | . The meal and stratum or the cells of the hippocampus are the excited |
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| 44:09 | projection cells. That means they will their axons exit out of this hippocampus |
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| 44:15 | of this area, hippocampus and project the other parts of the brain into |
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| 44:20 | other networks that are adjacent and interconnected this network. OK? And if |
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| 44:26 | look at these exciter perimeter cells, all look the same or politically |
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| 44:31 | ical basal axons going out, some them are a little shorter, some |
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| 44:35 | them are a little longer. Most the petal cells will live on the |
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| 44:40 | perimeter. In hippocampus, petal cells be comprising about 80 to 90% of |
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| 44:51 | of the cell population will be 80 90% or excited for petal cells and |
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| 44:58 | to 20% are the inhibitory interneurons in hippocampus. So, although petal cells |
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| 45:08 | quite abundant. They account for 80% of all of the neurons in the |
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| 45:15 | . They're quite abundant, but they're very diverse. They're not diverse. |
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| 45:22 | , 80% of those 80% will have in the perala layer. The only |
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| 45:29 | is some of them will have SOMA of peridol layer and some of them |
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| 45:34 | be CD positive, which stands for . So this is a cell specific |
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| 45:39 | that I was referring to earlier. of the parameter cells will be Calvin |
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| 45:44 | positive and others will not maintain And that's the end of the story |
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| 45:50 | they speak one dialect. So not interesting. What are all of these |
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| 45:59 | cells surrounding these kamal projection cells are inhibitory interneurons. So remember we talked |
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| 46:07 | local network inhibitory interneurons. OK. they're labeled here one through 21. |
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| 46:17 | that means that there are at least different subtypes of inhibitory interneurons. But |
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| 46:25 | is different about them? How do differ? Why are they all different |
|
| 46:31 | ? You can look at them and is their sauna. So some of |
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| 46:35 | live in from a dollar layer in and in orange are their dendrites. |
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| 46:39 | of them have dendrites going vertically, have dendrites going horizontally. And then |
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| 46:46 | purple processes here with yellow cups are synopsis. So this shows that some |
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| 46:53 | the inhibitor neurons will synapse on the of parameter cells. Others will synapse |
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| 47:00 | the basal dendrites and axons of petal . Yet others will synapse onto the |
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| 47:08 | dendrites of parameter cells. So, they're diverse, the inhibitor into |
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| 47:16 | They speak 21 different dialects. That that they have 21 different unique patterns |
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| 47:22 | action potential firing in some instances. look the same like number two and |
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| 47:29 | four, they may speak the same that's indistinguishable like number two and number |
|
| 47:35 | . So it's not exactly 21 maybe there's 18 dialects distributed over these |
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| 47:40 | cells. So how do we distinguish two and four? Look the same |
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| 47:45 | in the same way have the axons target the petal saloma speak the same |
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| 47:52 | . The only thing left the CCI and number two is positive for |
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| 47:58 | which is Perin, it's called basket Perin, positive basket itself. And |
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| 48:04 | four is basket cell, but it's for not a cellular mark or |
|
| 48:11 | Yeah. And that's how we know there are all of these different cellular |
|
| 48:17 | . If you wanna throw in molecular here from RN A sequencers, it |
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| 48:22 | probably change the picture a little Uh And as far as the exact |
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| 48:27 | of subtypes of cells, it may that number, it may reduce that |
|
| 48:32 | based on molecular analysis, precise molecular . And so for this midterm, |
|
| 48:39 | get this question quite often. Can go over the slide again and then |
|
| 48:45 | week later I get this question. you go over that slide again? |
|
| 48:51 | I urge you to do something after , I'm gonna have your four lectures |
|
| 49:00 | . In fact, if you go video points.org now and you log |
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| 49:05 | you will see that there are three three lectures already uploaded uh for your |
|
| 49:13 | . And your fourth video is going be uploaded today. As I |
|
| 49:17 | this is what I'm gonna do every halfway through the section which is typically |
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| 49:22 | lectures. I will upload those four and I will encourage everybody if you |
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| 49:28 | any questions or if you haven't been every lecture or if you have questions |
|
| 49:34 | specific material to please review those It's a really good time to review |
|
| 49:40 | . So then you can have four lectures, review those four more lectures |
|
| 49:45 | be well prepared for your first OK. So again, what do |
|
| 49:50 | need to know for the exam on slide? Well, campus, that |
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| 49:56 | familiar, right? We talked about structure predominantly three layer structure. You |
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| 50:00 | to understand that most of the cellular comes from the inhibitor interneurons. As |
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| 50:05 | inhibitor interneurons, they release gaba and control the output of these parameter cells |
|
| 50:13 | these parameter cells are projection exciter And there isn't that much diversity in |
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| 50:19 | excitatory projection cells uh as compared to the the. So really the the |
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| 50:26 | of output of activity from petal cells get determined how all of these different |
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| 50:32 | of inhibitory cells will interact with a excitatory cell. And then what else |
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| 50:43 | specific markers? So if you can't the difference between, so that look |
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| 50:47 | live in the same letter, speak same dialect, then you have to |
|
| 50:51 | something about their self specific expression. what self specific markers. Some of |
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| 50:57 | will express Pavol and how this will and some of them will express CCK |
|
| 51:02 | this will not. Um And uh don't talk about RN A sequencing or |
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| 51:08 | analysis, how it's done with these of experiments. So you don't necessarily |
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| 51:12 | to incorporate it into your knowledge base now. So from the very early |
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| 51:19 | when Ramona Cajal was using gold G , he started sub packing and reconstructing |
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| 51:26 | of these different neurons. But he started subtyping and reconstructing Leo cells. |
|
| 51:34 | so he already knew and in this , he showed Astros the Bergman Cell |
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| 51:42 | , he smooth, smooth for the , the valet of fibrous ostroy. |
|
| 51:50 | he started already describing different subtypes of . Uh and we're supposed to get |
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| 52:01 | Glia lecture today, but we're not to get through Glia lecture today. |
|
| 52:06 | very briefly gonna talk about short introduction GLIA. And I'll show you a |
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| 52:12 | of tools that you can use throughout semester and following these lectures and also |
|
| 52:18 | video lectures that I described there are major types of glia that will discuss |
|
| 52:24 | glia, oligodendrocytes, microglia and Rad glia are involved in development of |
|
| 52:33 | processes, neuronal migration and guidance. is neuronal migration? Where are neurons |
|
| 52:41 | ? Why are they migrating? Why they need guides? So, neurons |
|
| 52:45 | not born in their final destinations. a couple of specialized areas in the |
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| 52:51 | uh near the ventricles, one of that where neurons are born and then |
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| 52:57 | neurons have to migrate to find their destinations. In other words, the |
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| 53:04 | lobe neuron is not born in layer of the primary visual cortex. It's |
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| 53:09 | somewhere around the ventricles and then it to the occipital lobe where it establishes |
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| 53:15 | in its final destination. And in for it to migrate rad glia acts |
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| 53:23 | guides, they actually provide these processes serve as latices and neurons become cytoplasm |
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| 53:34 | with radio glia and use radio glia of a push themselves along to |
|
| 53:42 | So, radial glia are the Radial glial cells are also progenitor |
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| 53:50 | Some are found still in the adult and radial glial cells can become other |
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| 53:56 | cells or neurons during the early development this migration and placement uh uh |
|
| 54:04 | OK. So this is what we by neuronal migration and guidance oligodendrocytes as |
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| 54:10 | here are responsible for myelin or myelination therefore installation and support of neurons and |
|
| 54:18 | function of neurons. Uh astrocytes are here are the most abundant type of |
|
| 54:25 | cells and astrocytes very intricately controlled synaptic . They're involved in synaptic formation or |
|
| 54:33 | we call synaptogenesis and their end And uh in addition to patrolling and |
|
| 54:41 | synaptic activity, their end feed form portion of the blood brain barrier that |
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| 54:47 | is one of the police checkpoints for that want to cross from the blood |
|
| 54:53 | the brain and the thal cells of capillaries, as well as the end |
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| 55:00 | of the astrocyte glial cells. Microglial are the smallest and most mobile elements |
|
| 55:09 | there is an injury and there needs be a repair. Microglial cells will |
|
| 55:14 | their processes and then physically will move soma through the brain tissue toward the |
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| 55:19 | of the injury. So that's why are the most mobile units of the |
|
| 55:24 | that are responsible for the immune response the brain. And they release cytokines |
|
| 55:29 | call upon the immune response in the . If there is an injury, |
|
| 55:35 | , uh or some other undesirable nauseous astrocytes. Uh uh uh uh we |
|
| 55:44 | discussed the lid denroy and microglia they control and are influenced by growth |
|
| 55:52 | . Control synaptic genesis control synaptic plasticity homeostasis of the brain. Our brains |
|
| 55:59 | cells and structures live within a certain range and keeping brain activity and brain |
|
| 56:08 | within that normal dynamic range is really . And microglia together with astrocytes are |
|
| 56:14 | intricately involved in control of this I'm gonna ask you to hold your |
|
| 56:20 | for next lecture simply because I'm running of time. And the last |
|
| 56:25 | two things I wanted to show So if you see these links here |
|
| 56:35 | you click on them, they will you to. The videos were top |
|
| 56:43 | for you. And sometimes these videos have commercials again. I did this |
|
| 56:52 | youtube. So the commercials they come go can be whatever. I didn't |
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| 56:57 | them. I didn't put them but you can watch these videos and |
|
| 57:00 | really show very nicely this whole migration neuron along radio Glia. And so |
|
| 57:08 | will see in my slides, hyperlinks videos like this. Sometimes there will |
|
| 57:12 | hyperlinks to the articles that are P and that's a good way to just |
|
| 57:19 | on these things. The very last before you guys go, I just |
|
| 57:25 | make sure that you all know that you go to the video points, |
|
| 57:32 | , you have your folder and video . So this is what I see |
|
| 57:37 | your view might be a little bit , but this is where you |
|
| 57:42 | There are signs Tuesday, Thursday and first three lectures, 123 are uploaded |
|
| 57:50 | . I'm gonna upload the fourth lecture you click on that lecture. If |
|
| 57:57 | bring it up after a while, will be a transcript here. You |
|
| 58:03 | in with your Cougar nut ID Um sometimes it may take a second for |
|
| 58:10 | lecture to load up. But the feature is that you can scroll through |
|
| 58:17 | you don't have to watch the whole . If you just want to repeat |
|
| 58:22 | material or review the material on the subtypes of inhibitor cells in the |
|
| 58:29 | Then the end of lecture four is good spot to to do it |
|
| 58:34 | OK. Thank you very much for here and I will see everyone back |
|
| 58:38 | Thursday. I hope to see |
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