Why can't most neurons in the central nervous system be replaced?
397258
During prenatal development, enough "stem cells" differentiate into neurons that each newborn infant has enough multipolar neurons to last a lifetime.  While neurons die continually throughout the life span, barring accident or disease, we still have plenty of neurons left, even into the 2nd century of life.\n\nHowever, certain diseases (e.g., Alzheimer's Disease) cause premature and widespread death of neurons - with devastating results.  \n\nOne of the great hopes we have for stem cell research is that there is very promising data from animal models that "flooding" a neuron-depleted area of the brain with stem cells can repopulate the lost neurons and reform the neural network.
178415
I am not familiar with the specific situation of this question.  However, if your question asks if neurological damage is "cast in stone", the answer is "no".  Neurons, axions and dendrites will replicate and form new pathways.  The process for cell mitosis and regeneration of the nerve tissue is much, much, slower than that of, for example, skin tissue.  The relative age of an individual will also play into the a major role in the outcome.  Clearly, someone who has reached advanced old age will probably not improve.
19730
The brain is not composed entirely of neurons.\n\nHere's some pertinent info:\n\nThe "cast of characters" (cell types) in the fully developed central nervous system (brain and spinal cord) is small: we have neurons, astrocytes, oligodendroglial cells, microglial cells, ependymal cells, blood vessel cells (endothelial cells) and a few remaining primitive (neuro)ectodermal cells. Any of these cells can become a tumor. Here they are: \n\nAstrocytes can become astrocytomas \n\nOligodendrocytes can become Oligodendrogliomas \n\nMicroglial cells can become a Microglioma which is now called a Primary nervous system lymphoma \n\nPrimitive ectodermal cells can become Primitive Neuroectodermal Tumors PNETs such as a Medulloblastoma \n\nEpendymal cells can become Ependymomas
463192
We use 100% of our brain-or at least 100% of our brain sense signals and uses oxygen and glucose.  Any neuron which does not connect with another and depolarize occasionally will probably die.  I have no idea where this myth came from, unless it was from studies of learning and memory.  We can learn a great deal more than most of us do-any average person could learn multiple languages, become expert in a number of fields, etc, but we don't.  This doesnt mean we dont use our brains-learning is more likely the generation of new pathways, connections, etc.  So it may be that we only learn 10% of what we could (put this way, it would be closer to 1%).  The majority of the brain is set aside for motor and sensory system integration- It takes an enormous amount of brain power to just perform our normal movements and to interpret and filter all the huge amount of sensory information we get every second-*That* is the primary action of the cortex.
1180691
because the body cannot live without BRAIN
746330
Every function imaginable, because the nervous system is the pilot of all body systems. Without the nervous system all other systems would be obsolete.
509717
neurons are the sensors whish transmits the signal in the brain, so the statement sounds to be wrong
921540
It's different for each tissue in the body... some examples are: epithelial (skin) cells: 1 month, or neurons (brain cells) : 50 years.
183293
Stem cells have been found in the brain. These can become nerve cells and reconnect the same as the missing cell. Also, the brain/mind is flexible in that other parts can be used to replace the parts that aren't working. I think with memory it can also be missing Nitrous Oxide.\nAcetylcoline and seratonin are chemical messingers. They must be made all the time. \nI have heard the first 6 months are the most beneficial recovery. After that the recover is less apt and slower. Don't take this too seriously. Talk to the doctor, neurolgist for real information.
640083
neurons are smaller. neurons make up a nerve.
886052
neurons are made of molecules  ( which are made of atoms ) but the activity is not on that level ( you might as well ask about the molecules in an extension cord )
775248
Neurons have the same organelles as other cells.  They have nuclei, mitochondria, ER, etc.  But, neurons may have higher numbers/concentrations of certain organelles because neurons use a lot of energy in maintaining ion concentrations and they secrete a lot of stuff (neurotransmitters).  I'm not sure how specific you need information, but "Principles of Neural Science" by Kandel is a great resource for all things neuroscience.  \n\nAs for the G0 phase stuff, although most neurons appear not to be able to undergo mitosis, this is not entirely true.  Recent research indicate that neurons in the olfactory bulb and hippocampus seem to undergo mitosis.  Why most neurons are in G0 isn't completely understood, but it may be something within the environment rather than the cell itself.
272344
Everything but the brain.
451320
Just a word of confirmation- Neurons are not the only players in transmission- There is increasing evidence that glial cells can transmit is "spreading waves" by depolarization.
684187
There are processes of regeneration going on, but getting cells to specifically differentiate to take on those roles is still in its infancy. It also depends on how the brain was damaged and what parts were damaged. Stem cells are omnipotent which means that they can differentiate into any kind of cell, but a culture is very hard to maintain and the success rate of transplant is still very low.
406389
It is well-established that the human brain has the capacity to take in an infinite amount of knowledge and information, far more than our 80 years of life allows.  It is also well-established that the human body is constantly repairing, renewing and replacing itself, and should go on doing so.  The human body, by design, should live forever and should be forever young. The  medical field cannot understand why it is not so. These two facts alone demonstrate that this life, logically, is not all there is.
870080
Good question.  Neurons do not regenerate, and do not divide.  This is why nerve damage is so severe (i.e. Multiple Sclerosis).  Neurons are said to be at the END of cell lineage.  There are of course exceptions, but for all intents and purposes, this is all you need to know.