Where do the new neurons come from? Cellular division?
probably. Or the reconfiguration of old ones. But I'd go with cell reproduction/division.
No neurons do not reproduce through mitosis (cellular division). There are however stem cells in the Nervous system that will differentiate into neurons.
The number of neurons produced from stem cells is very small, and from what I understand they only differentiate when damage occurs to replace the damaged or dead neurons. The number of neurons that are replaced from stem cells are small, thats why almost all paraplegics do not recover from their injurys.
You're correct that it's the neural stem cells that are undergoing cellular division, not the differentiated neurons. But, as for how many and when, that's not necessarily true. What's important, though, is where the stem cells are located. They are predominantly in the brain, not the spinal cord, so don't reach areas of spinal injury. Also, spinal injuries are damaging long axons, not necessarily cell bodies, so even if the cell bodies are replaced, restoring the growth of the axons to the right places, in the absence of the "directional signals" that are present during development, can take a very long time, if it occurs at all (or the growth can be misdirected). So, lack of neural stem cells isn't really the reason why paraplegics don't recover (or recover very slowly).
I read an article today about exercise and a link to neurogenesis.
One comment was - "Brain cell production can occur throughout life, even as people advance into old age."
The point was that one should exercise throughout one's life - and not just to maintain muscle tone and good cardiovascular performance, but also because exercise is important with respect to the brain. Apparently exercise does stimulate neurogenesis. If sounds intriguing, so I plan to research this.
One claim is that exercise helps generate new brain cells, and a second claim is that it strengthens connections between those cells.
Look for a book by Dr. John Ratey (Assoc. Prof. Psychiatry, Harvard Medical School), "Spark: The Revolutionary New Science of Exercise and the Brain".
I've heard that constant reading and learning and mentally challenging yourself keeps the brain generating new cells, and keeps the brain sharp. I've read some studies, maybe I can find them. I don't know how physical excersize would though.
I don't know about new cells, but exercise can't hurt maintenance of existing cells. Which is enough reason for me to exercise.
Even better, I think short-term gains are considerable.
On a related matter, I remember reading about studies which indicate physical activity (in addition to emotional/human contact) being essential (not just "preferable") in brain development during childhood.
I haven't seen the studies on that, but I would imagine the same way mental exercises would help, but maintaining or strengthening the pathways for motor function, coordination, sensory input, etc. Or, perhaps they're just referring to generally maintaining good health...better blood flow and nutrient utilization for all cells, including those in the brain. It's an interesting point.
Moderate exercise can improve one's hormones and mood. Married men also tend to do better in general. Sex between a close couple tends to improve people's hormone balance better than masterbation or sex with strangers.
An MRI study showed that the more intelligent the person, the less work their brain did going from A to B. They don't get hung up on tangential subjects as someone with an emotional difficulty or chemical imbalance might. Instead, they are focused in the moment, and apparently so are their body functions.
I would agree it can't hurt. I wouldn't give up continued mental activity for physical in hopes of maintaining mental acuity, however. Think Stephen Hawkings.
Certainly, use of the brain stimulates 'connectivity'. I think it helps the brain develop just as exercise helps muscles develop. Basically, it's a case of ,use it or lose it'.
Anyway, according to the article I was reading, each time a muscle tenses and relaxes, chemicals are released into the body (I assume through the circulatory system). One of the chemicals is the protein IGF-1, which apparently facilitates the production of "neurotrophic factors".
One particular neurotrophic factor, brain-derived neurotrophic factor (BDNF), prompts brain cells to reproduce rapidly.
People who exercise have higher levels of neurotrophins.
So exercise and mental activities such as"constant reading and learning and mentally challenging yourself keeps the brain generating new cells, and keeps the brain sharp." I think my paternal grandfather is a great example. He was a voracious reader and was mentally sharp up through his last year at age 103 yrs.
Exercise and diet for the mind/brain
More studies showing that exercise is beneficial to maintaining a sharp mind or mitigating deterioration.
Memory: Forgetting Is the New Normal
Not only exercise but diet -
I love blueberries, blackberries and raspberries!
The article was written by Sue Halpern, author of CAN'T REMEMBER WHAT I FORGOT: THE GOOD NEWS FROM the FRONT LINES OF MEMORY RESEARCH, Harmony, May, 2008.
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