Naked Science Forum
General Science => General Science => Topic started by: moses lawn on 23/09/2004 10:59:10
-
Given that every cell in my body is being replaced at regular intervals, and the cells I am made up of now are mostly all different to those that constituted my body, say, 20 years ago, how is it that I am the same person as I was then?
-
You're not !!..I know I am most certainly a different person to the one I was twenty years ago, even five years ago probably, but, I think I know what you're getting at and I'm sure the answer is in DNA, your building blocks programmed to make you the way you are and rebuild you with less efficiency as we get older (hence ageing)...though the ageing thing may also be to do with life long exposure to natural radiation, ie: sun rays etc
Your mind is you and I think this is one of those big questions which philosophers and the like have debated for years and years, and probably will continue to.
I may be entirely wrong (usually am[:(]),so keep an eye out for some answers from the experts.
'Men are the same as women...just inside out !' (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.de%2Fhtml%2Fimages%2Fsmilies%2FSchilder2%2Finsanes.gif&hash=4f18432872d0188852a6f4a3170ec758)
-
Neil, how can you say you're usually wrong??!! I happen to dis agree. In fact you're very right on this one.
As neil pointed out the most important parts of why you are you have to do mainly with your life experiences and nothing to do with your cells or how often they divide. But physically speaking, it is your uniuqe genome that makes you you. Every cell in your body started from one cell and there for has inherited that cell's genome which keeps getting passed on.
There are chances for this genome to change from environmental factors taht cause mutations. There are most likely a numer of cells in your body that have undergone small muations at one point in your life or another..... and all the cells taht came from these cells, and the ones that came from them etc. Carry that mutation. So in that sense, you're NOT actually who you were 20 years ago :)
That's no moon.... its a GRAPEFRUIT!!!!
-
Just to correct a small inaccuracy in the original question which stated that every cell is being replaced at regular interval; this is not correct.
A large number of cells in the body exist in a fully differentiated, non-dividing state. What you are born with has to last a lifetime.
Examples of cells that are not replaced include neurones (excepting the small, fairly localised sites of neurogenesis in the brain), and muscle cells, including cardiac (heart) muscle. Women's ovaries also contain eggs which cannot be replaced once they are gone (hence women undergo menopause at around age 50).
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
-
skeletal muscle cells can generally regenerate, there are 'satellite cells' that sit around waiting until they are called upon to become more muscle. this is why we can build up more muscle by exercise - we are activating these satellite cells. the question is, do these 'muscle men' use up their reserves of satellite cells, or are they replenished? when muscle doesn't regenerate then we see muscle wasting, which can be seen in AIDS patients and muscular dystrophy. but yes, the heart you are born with is the very same one that you'll die with, so look after it!!
-
I saw a show (the BBC life series with the guy with the beard) that stated that we do not contain any cells that are older than ten years, apart from our eyes. Also, in some recent experiments with mice, they found that if they made a mouse turn blue, after a period some of it's ova were also blue. Apparently, this put some pressure on the thoery that women are born with their full complement of ova. I believe more tests are being completed, but so far, the results are inconclusive.
-
by what method did they make this mouse turn blue? (I actually think I've heard of "blue mouse experiments" before. But I'm not sure it its a cellular dying, a blue protien thats expressed, etc.???
anyone know?
That's no moon.... its a GRAPEFRUIT!!!!
-
chris, I heard that the whole of the brain is replaced within a decade???? not just localised parts... allthough this was on a gee-whiz tv documentary.
wOw the world spins?
-
In body building, the increase in strength and muscle bulk is achieved through the production of additional contractile filaments within each muscle cell (so each cell hypertrophies (becomes larger)) rather than an increase in the physical number of cells.
In the same way, if a person eats too much and becomes fat, the size of the individual adipocytes (the fat-storing cells) enlarges to accommodate the increased cargo of fat. This is why liposuction works - once the cells are removed they are not replaced and hence the weight is not reaccumulated in the same body region. The only time fat cells divide is in babies and young individuals. Hence it is important not to overfeed babies because they can develop too many fat cells (hyperplastic obesity).
But, as fishytails points out, more recently muscle progenitors, satellite cells, have been identified sitting within adult muscles and making up between 1 and 5% of the total cell count. These undifferentiated cells act as the muscle's inbuilt first aid kit and can repair limited muscle damage. However, there are limits to the extent of repair possible (if you disrupt the muscle structure too excessively then the muscle has no 'template' for regeneration), although the cell count does not seem to deplete with time. Here's an excellent review on the subject :
http://www.rbej.com/content/1/1/101
Chris
"I never forget a face, but in your case I'll make an exception"
- Groucho Marx
-
didn't someone in here say they worked with blue mice at some point???
That's no moon.... its a GRAPEFRUIT!!!!
-
Justy...thanks for your affirmation of my getting something correct..it's just that I know on this site I'm surrounded by clever academics...and I ain't one of em !!.....I'm so full of self doubt...I'm not even sure that it's me typing this !!..but cheers mate.
'Men are the same as women...just inside out !' (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.de%2Fhtml%2Fimages%2Fsmilies%2FSchilder2%2Finsanes.gif&hash=4f18432872d0188852a6f4a3170ec758)
-
quote:
Originally posted by MayoFlyFarmer
didn't someone in here say they worked with blue mice at some point???
That's no moon.... its a GRAPEFRUIT!!!!
Last year sometime, I think she has since stopped contributing.
Did a quick site search. I dunno how to link it, but it was topic ID 475 and the poster was Kitten.
-
quote:
[I dunno how to link it, but it was topic ID 475 and the poster was Kitten.
Rob,...just right click on the page that you want to link to and you'll get a menu. Scroll down to Properties and left click it, you'll get the properties tab and there you'll see Address (URL)....just copy and paste into your text...for instance the link to this page is http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=1349 ...try it... you can also use it to link to any other page on the internet
'Men are the same as women...just inside out !' (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.de%2Fhtml%2Fimages%2Fsmilies%2FSchilder2%2Finsanes.gif&hash=4f18432872d0188852a6f4a3170ec758)
-
http://www.thenakedscientist.com/forum/topic.asp?TOPIC_ID=475
Like that, you mean. Thanks, Neil.
-
A Christian idea that is important even though all the water is flushed out of the body is that a sin commited with the body is more serious because the body is eternal and it's history never changes. Thus the seriousness of sex sins compared to phantasies or thoughts and desires. The soul and spirit can be renewed and recreated powerfully but you body is forever with a history.
I don't comprehend this well. Since Jesus blood was shed for sins and His blood is meant to be the highest reality which consumed all sin's reality on the cross. Why cannot our blue prints be sacred blood transformed and why cannot we have altogether new material...?
When Adam sinned somehow this was stored in His blood and passed down to all of us.
Our DNA in some cells is kept. Our memories remain, thus neurones are the same, and our bones cells are the same, and our psyches are the same ones altered by decisions.
Titanscape
-
You know in india it is believed that our body is made up of five basic elements.these are Earth,Water,Fire,Air and Space.These five elements are controlled by electricity of the body known to us as bio-electricity.This current of electricity comes from this non-changeable life battery.This battery has been installed in our body at the time of conception.The white dazzling light generated by this battery can be seen in the middle of forehead with eyes closed,through certain yogic methods.Many people have seen this light.
Out of this battery electric current passes in the body through lines.These lines are called as meridians.They start from the tip of each finger of the right hand,go all over the body and end in the toes of right leg and so also on the left hand side.Now so long this current of electricity flows properly in the body,the body remains fit and healthy.If for any reason this current does not reach any part of the body,there is malfuntioning of that part of the body accompanied by pain in some cases.
victor
-
Chris, I wondered why liposuction wasn't a cure for obesity, because I've seen our liposuction patients return a year later just as fat as they once were. Apparently the remaining fat cells just get bigger, so you can gain weight after liposuction, and in the same areas too. Then other times I've seen it where there's weight gain but in different areas. I guess it depends how much fat they suck out.
-
quote:
by what method did they make this mouse turn blue? (I actually think I've heard of "blue mouse experiments" before. But I'm not sure it its a cellular dying, a blue protien thats expressed, etc.???
not sure about blue, but I've heard of fluorescent green mice. scientists can make 'transgenic mice' which is basically the addition of a gene (or disruption of a gene to knock it out) to the mouse DNA, so when it grows up it expresses this new gene. There is a protein called GFP (green fluorescent protein) which, as you'd expect, fluoresces green, and when 'put in' to a mouse in this way can cause it to glow.
This is a good site:
http://www.fluorescentpets.com/prod02.htm
-
actually, now i come to think of it .... the lacZ gene can be put into mice to cause expression of beta-galactosidase. This causes cells to turn blue when incubated with X-gal. I'm not sure if you can see live blue mice though, this technique is most commonly used with bacteria, and teh X-gal is added to the culture medium.
-
I exchanged messages with Kitten, and she apparently was successful at transplanting a gene and making a blue live mouse. She said that was the pinnacle of her career. I wish she would come back and visit the site!
----
John - The Eternal Pessimist.
-
I just read and I quote:
"it has been suggested that there isn't a single bit of any of us -not so much as a stray molecule- that was part of us nine years ago. It may not feel like it but at the cellular level we are all youngsters"
Source: Bill Bryson :A Short History Of Nearly Everything...page 453 Chapter: CELLS.....
'Men are the same as women...just inside out !' (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.world-of-smilies.de%2Fhtml%2Fimages%2Fsmilies%2FSchilder2%2Finsanes.gif&hash=4f18432872d0188852a6f4a3170ec758)
-
Back to moses lawn's question -- you are confusing information with matter.
The illusion of consciousness is the product of memes -- units of infomation -- not molecules. Although your cells are constantly being replaced, they're very similar to the old ones, so the information content doesn't change.
It is the information content of the relationships of the molecules in you (most importantly in your brain) that make you who you are. This, of course, also changes with time as you learn more and change your opinions on things, but that isn't really relevant to your question.
I can picture in my mind a world without hate, a world without war.
And I can picture us attacking that world, because they'd never expect it.
-
Actually, this may seem a relatively simple question when dealing with human beings, but what happens when one asks the same question with regard to ants?
In a colony of ants, every ant (excepting the queen) will have the same DNA. In many other ways, individual ants do not act as individuals, but as component parts of the group, just as an individual human cell will merely play a role in the human body. What is the true individual, the single ant, or the total colony?
In any event, if one were to use DNA as a definition of self, this would cause problems in defining the individual when dealing with identical twins.
Is the issue of an indivisible individual really so much a biological fact, or an illusion of visual perception, that the eye cannot distinguish the constituent parts within one body, and yet can see the gap between bodies, and so will visually decide where the boundary of one body is separate from the boundary of another? In the same way, in the time domain, the visual image of the individual is something that is perceived to be visually contiguous over time.
Ofcourse, the notion of conciousness is also dependent upon the concept of self determined within the brain, but that self (while maybe is the primary issue in moses lawn's question) does not fully relate to identify individuals who are not of oneself. Even in the sense of self, I suppose we are talking, if not specifically about continuity of visual perception, but nonetheless in the broader context, continuity of perception (i..e. tactile, and other sensory information pooled by the brain).
George
-
But how do you know you are thinking at all or is it one of the 60,000 then?[:D]
What you do speaks so loudly that I cannot hear what you say.
-
quote:
Originally posted by Hadrian
But how do you know you are thinking at all or is it one of the 60,000 then?[:D]
And another 59,999 to go before I run out of thoughts for the day. [:D]
George
-
back to counting the head banging, no wonder orgasms hurt so much. [:D]
What you do speaks so loudly that I cannot hear what you say.