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Question about neurons


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OK I read that some neurons are in your body for life. Are organelles in these neurons replaced?

What about nucleus and mitochondria?

 

Mitochondria can divide independantly of the cell so I presume that they are replaced from time to time. Or perhaps not - do I remember something about the number of mitochondria in each cell declining with age, or is only specific cell types that this is the case?

 

The nucleus however remains for life although the DNA probably undergoes repairs from time to time, but it is not entirely replaced or duplicated in a short time period as in cell division.

Edited by Greg Boyles
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Are all parts of DNA repaired or some parts?

Also what happens to "old" parts of DNA?

 

Also what about nucleolus and RNA?

 

Also are there parts of neurons that are replaced and parts that aren't?

 

Also which part of the neuron produces/receives input?

 

And when do axons/dendrites get repaired?

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Most organelles have a turnover. Same goes for proteins, lipids etc. If your question is whether the molecular make-up of a neuron is static, then the answer is no. The components are more or less in a coordinated flux.

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I read that axons and dendrites are only replaced when damaged.

Also when organelles die arent they recycled?

 

And yes I know parts of neurons move around and change.

 

As I recall around puberty there is a pruning of neurons. I know we now know there is more plasticity of the brain throughout adulthood than was once thought.

 

I had long had a question of the energy source of brain cells. They need to be bathed in glucose but only recently have they found the insulin that enables glucose to go into the cells. Perhaps these types of cells would, oddly enough,do less "work" than other cell types. They could then afford to be more longlived?

 

I just read of the "tip of the tongue" phenomenon. People have the memory but in the frontal lobes they don't have the ability to access it as they age. Is the shrinking of the frontal lobes representing cell death or poor energy utilization? It seems kind of odd that those memories do retain within us stored somewhere.

 

 

 

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Are all parts of DNA repaired or some parts?

Also what happens to "old" parts of DNA?

 

Also what about nucleolus and RNA?

 

Also are there parts of neurons that are replaced and parts that aren't?

 

Also which part of the neuron produces/receives input?

 

And when do axons/dendrites get repaired?

 

RNA is not a permanent store of genetic info anyway, so that is turned over continuously throughout the cells life.

 

I presume that certain parts of neurones, e.g. cell membranes, membrane protiens, etc are continuosuly repared or replaced, it would be hard to conceive otherwise in such a dynamic system.

 

But axons are not replaced - that is why when you get a spinal injury you are paralysed for life?

 

Dendrites are a different matter, these nerve connections are continuously altered and replaced and re-connected over time. This is fundamental to the process of learning and memory etc.

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Are they all changed or only when you learn something new, etc.

 

Those dendrites and nerve collections associated with long term memories are permanent I guess, otherwise you would loose your memories. But those associated with short term memory, such as where did I park my car 20 minutes ago, are lost. There are 3 types of memory I believe - short term (where are my keys), medium term (a dance routine for a concert next month) and long term (my name and birthday). Indicating how long the denedrites and synapses last.

Edited by Greg Boyles
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Those dendrites and nerve collections associated with long term memories are permanent I guess, otherwise you would loose your memories. But those associated with short term memory, such as where did I park my car 20 minutes ago, are lost. There are 3 types of memory I believe - short term (where are my keys), medium term (a dance routine for a concert next month) and long term (my name and birthday). Indicating how long the denedrites and synapses last.

 

Actually, when you recall something it does affect the connection that fire when it is recalled. That is one of the reasons memories can be altered and such.

 

Also, as far as I know, forgetting isn't necessarily associated with the synapse connection per se, if only because memory isn't nearly that simple.

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Actually, when you recall something it does affect the connection that fire when it is recalled. That is one of the reasons memories can be altered and such.

 

Also, as far as I know, forgetting isn't necessarily associated with the synapse connection per se, if only because memory isn't nearly that simple.

 

Laying down of memories does involve formation of new synapses however. Loss of short term and memories certainly does involve the loss of temporarily formed synapses. No matter how hard you try you would never recall, in detail, an incident where you were trying to remember where you parked your car upon exiting the shopping centre 2 years ago for example.

 

Inability to recall a longer term memory probably possibly does involve loss of some synapses in the pathways that allow you to access a stored memory, but not necessarily loss of synapses associated directly with the memory.

 

The CNS is quite dynamic and unused pathways are alomost certainly 'pruned' to some extent. When you do attempt to re-call a rarely accessed memory, whose pathways have been pruned, presumably you end up accessing the memory via an indirect patway and therefore require greater effort in recalling it.

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Laying down of memories does involve formation of new synapses however. Loss of short term and memories certainly does involve the loss of temporarily formed synapses. No matter how hard you try you would never recall, in detail, an incident where you were trying to remember where you parked your car upon exiting the shopping centre 2 years ago for example.

 

Inability to recall a longer term memory probably possibly does involve loss of some synapses in the pathways that allow you to access a stored memory, but not necessarily loss of synapses associated directly with the memory.

 

The CNS is quite dynamic and unused pathways are alomost certainly 'pruned' to some extent. When you do attempt to re-call a rarely accessed memory, whose pathways have been pruned, presumably you end up accessing the memory via an indirect patway and therefore require greater effort in recalling it.

So are old dendrites reused in the same way other old organelles are?

 

Also is it true that the only waste products of cells are co2 and lactic acid???????

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Laying down of memories does involve formation of new synapses however. Loss of short term and memories certainly does involve the loss of temporarily formed synapses. No matter how hard you try you would never recall, in detail, an incident where you were trying to remember where you parked your car upon exiting the shopping centre 2 years ago for example.

 

Inability to recall a longer term memory probably possibly does involve loss of some synapses in the pathways that allow you to access a stored memory, but not necessarily loss of synapses associated directly with the memory.

 

The CNS is quite dynamic and unused pathways are alomost certainly 'pruned' to some extent. When you do attempt to re-call a rarely accessed memory, whose pathways have been pruned, presumably you end up accessing the memory via an indirect patway and therefore require greater effort in recalling it.

 

I'm not saying at all that you were mistaken that synapse connection plays a part in memory loss and forgetting; I only meant to say that it is much more complicated than that because of all the different facets of memory, recall, and the like. Just like your parking example, just because you remember, in detail, an incident involving a family member that happened 2 years ago doesn't mean it's a true memory.

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What is it that you want replies about?

 

I believe there is a building and deconstruction aspect in relation to tubulin in reference to the recycling of dendritic spines. Probably also in reference to dendritic shafts, although my cellular biology knowledge is lacking in this department and I am tired at the moment. I believe the cellular construction of dendritic spines is quite contemporary, cutting-edge knowledge at the moment.

 

Is it done in the same way? Mmmmmm... No, I don't believe so, because I believe there are transport modules that help the proteins go into place...

 

http://www.ncbi.nlm.nih.gov/pubmed/14704952

 

Organelles can be attached to the cytoskeleton, but I don't believe the generation of those organelles is the same as generating dendritic networks. Again, you'd more than likely want a hardcore cytologist to talk to about this. Perhaps there are enough evolutionary correlates to consider it the same, but I don't know cellular biology on that level well enough to say yes/no.

 

I believe there is a bunch of actin construction and deconstruction that occurs due to remodeling of neural synapses, which are due to stimulation (or lack of) of neural networks.

 

In reference to your last question, I don't think so. I would consider the peroxide ions and other junk to be waste if released improperly, but I'm not a biochemist, so I can't correctly answer the question.

Edited by Genecks
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Ions are using by the cell to establish and alter membrane potential and other physiological actions by the cell.

And ions can be considered parts.

 

What is your particular goal in asking these questions?

 

I gave you some nice links that go into some detail in discussing the philosophy of consciousness, even some discussing how neuroscience plays into all of it. Otherwise, much is yet to be discovered about neuronal cells. Many people hope they can generate a model of the nervous system based on the neural coding that exists rather the extreme levels of cellular biology involves. However, I often considered that method without the reductionist cellular biology to be a poor statistical approximate of what is really going on in the nervous system.

Edited by Genecks
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It is correct that most neurons of the body have life span equal to the life span of the individual.

 

Some of the organelles are constantly destroyed and reformed, while the major ones like nucleus will have to stay there for life. Internal repairs to the DNA and membrane of nucleus do occur from time to time.

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  • 2 weeks later...

Apparently neurons present in the hippocampus and amygdale have the ability to repair themselves after injury. We already know from Maguire et al. that the hippocampus can change its shape in conjunction with the demands that are placed on it, whether this can be classed as neuroregenesis is debateable but the facts remain clear that we will never truly understand the complexities of the brain.

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