Ok... so...
You yawn when you have a lack of oxygen to the brain. This I know.
So... Why is it that you yawn when you're tired/bored? You figure you'd yawn when you wake up, to get oxygen to your blood that you may have lost with slower breathing. The reason why I think this, is because you have been breathing all day, and you'd have more than enough oxygen floating through your blood.
So, I guess my question is... why do you yawn when you're tired if yawning is caused by a lack of oxygen?
You yawn when you have a lack of oxygen to the brain. This I know.
So... Why is it that you yawn when you're tired/bored? You figure you'd yawn when you wake up, to get oxygen to your blood that you may have lost with slower breathing. The reason why I think this, is because you have been breathing all day, and you'd have more than enough oxygen floating through your blood.
So, I guess my question is... why do you yawn when you're tired if yawning is caused by a lack of oxygen?