Yawning, what is it for?

Hi,friend,our body is as like as a mchine made for work upto 100 years.Mean while we are giving over stress to our bodies,..not sleeping/giving rest sufficient as per medical norms... When we feel sleepy and when our body requires rest..slowly we yawn... Have a mice sleep my friend..........

When the content of carbon dioxide is too high, the brain sends signal to ignite yawning, which takes about 6 seconds. During yawning, related organs will be benefitted. Some exercises help to initiate yawning or tears, both said to be good for health.

when we are tired or sleepy but cannot have a rest or go to bed, we need more air to refresh ourselves. the we yawn. have you ever noticed that when we yawn, we take a long and deep breath, thus we can take in more air. but i don't know why it is contagious. perhaps other's yawning reminds us of our own tiredness.