[chat250 (OP)]

I dont know if i spelt 'yawn' right but what I mean is when you tired and you open you mouth and take a deep breath

[Quantumcat]

It's because you are so tired that you don't breathe enough, the brain is a little deprived of oxygen and makes you take a deep breath to get more oxygen for itself.

Am I dead? Am I alive? I'm both!

[Exodus]

You can also consider the reciprocal in that you are expelling more CO2.

Resident Tour Operator - The Naked Scientists

[Broca]

I think there are some thoughts that a yawn can be a phisiological response as well. Like, if you are watching someone eat, you become hungry. I know when I see someone yawn, I oft times will yawn as well.

[Ians Daddy]

I yawned while reading this. Seriously. Just thinking of a yawn.

[Quantumcat]

I think when you yawn when someone else yawns, it's because you see someone else yawn, your brain realises there might not be enough O2 in the air, and makes you yawn too. Corret me if I'm wrong, though

Am I dead? Am I alive? I'm both!

[bezoar]

I yawn a lot when I'm too cold.

Bezoar

[cuso4]

May be it's because your body needs more oxygen for respiration, so you can generate energy to keep warm?

Angel

[chris]

Angel - where have you been, not seen much of you lately !

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[Qing]

I start yawning when I start reading this topic.[] (only because I see you talking about yawning)
has anyone experienced yawning continuously for a long time and you think you can't stop yawning.[?]

Qing

[cuso4]

quote:Originally posted by chris

Angel - where have you been, not seen much of you lately !

Chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

I have been around, just didn't post much. Sometimes discussions become too complicated and I don't know what to post. I'm back now that my brain switches on again after a long break.

Angel

[mm]

how does the brain get the information that we need more oxygen? how does the brain 'realise' that we need to yawn too when we see others yawning? I know that our brain is amazing but, can someone actually explain to me 'how'? Cheers~   [?][|)]

[chris]

The brain uses detectors in the arteries (aorta and carotid) to provide information about arterial gas tension and pH which it uses to co-ordinate breathing accordingly.

As you become hypoxic (low on oxygen) the brain increases the rate of respiration to compensate. Similarly, if the level of carbon dioxide rises, and the pH falls (due to rising carbon dioxide and / or the presence of lactic acid) the level of respiration rises to 'blow off' more carbon dioxide.

For this reason mountaineers at high altitude hyperventilate (involuntarily) to maintain oxygenation. This drives off carbon dioxide, making the blood alkaline and causing some of the symptoms of altitude sickness.

It also gives rise to a strange breathing phenomenon call Cheyne-Stokes breathing where people breathe rapidly for a short while, then stop breathing for ages, then resume rapid breathing again.

chris

"I never forget a face, but in your case I'll make an exception"
 - Groucho Marx

[bezoar]

Thanks Chris,
I never knew the actual mechanism for altitude sickness.  Why are some people more susceptible than others.  I've never felt particularly affected by altitude in say Denver, Colorado whic is over a mile high, and Mexico city.  But, I've been with fellow travelers who got terribly sick and had to take to the bed.  Any reason for the variables in sensitivity -- other than the obvious, smokers vs non-smokers?

Bezoar

[another_someone]

Thanks Chris,
I never knew the actual mechanism for altitude sickness.  Why are some people more susceptible than others.  I've never felt particularly affected by altitude in say Denver, Colorado whic is over a mile high, and Mexico city.  But, I've been with fellow travelers who got terribly sick and had to take to the bed.  Any reason for the variables in sensitivity -- other than the obvious, smokers vs non-smokers?

Bezoar

I know this is a long dead thread, but since it was referenced from http://www.thenakedscientists.com/forum/index.php?topic=11935.msg145535#msg145535, I thought I would respond anyway.

My understanding is that the variability in response to altitude is down to the number and efficiency of your red blood cells, which alters you efficiency in transporting oxygen.  As you acclimatise to high altitude, the number of red blood cells in your blood stream increases, and so you are better able to tolerate the low oxygen supply (this is also a reason athletes like to train at high altitude, since as their red blood cell count goes up, so does their ability to burn more energy (at any altitude).