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Biology/Cell Replacement


QUESTION: Some have said that about every 7 years every cell in the human body is replaced. I read up on that and I guess that is about averages and doesn't include neurons in the brain which never get replaced?

What if brain neurons also got replaced with new cells? What would happen? I often think mine aren't holding up so well.

ANSWER: Hi James
First of I can assure that the 7 year thing is a nice story but it is not true because cells have different life spans. The only cells that live for 7 years are most muscle cells and the nerve cells. Your learning and memories are contained within the brain tissues so if you brain was replaced you would have start all over again learning your three R's and everything that you know.
 Cells in the body are dying at different rates and the loss is balanced by new cell division(except in nerves and muscles). The death of cells is called apoptosis. When apoptosis is greater then new cell division you lose tissue. When cell growth is greater then apoptosis you have a tumor
  By the way cells outside the body are immortal. Given the proper nutrients they will live forever, but once the are a part of the body they eventually die and so will the body

---------- FOLLOW-UP ----------

QUESTION: What gives the culmination of brain cells my memories? Can't a cell's position and connections be replicated?

Although there are still mysteries about memory The current explanation is that every thought or sensory input involves a nerve impulse moving in the same pathway. I other words when you see the color blue the impulse the pathway a-b-c-d-e. It were to follow a-d-e-c-b your thought would be green. Actully thoughts change quickly. If they did not whatever you are thinking at this moment would think the same thing the rest of your life


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Walter Hintz


Science teacher for over 50 years. MSc. in biology. I can answer questions in general biology, zoology, botany, anatomy and physiology and biochemistry.


I have a MSc in biology and have been a science teacher for over 50 years. At present I am a faculty member at a college and a science consultant at seven catholic schools.

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