when you are tired why do you cry ?

Answer 1

There are two possible explanations:

1- During a yawn, there is a slight increase in pressure inside the skull (likely caused by slight increases in the amount of oxygen taken in during a deep yawn). This causes the cerebrospinal fluid (CSF), the fluid that surrounds the brain and flows through the brain's ventricle system, to be forced out faster than normal. That fluid enters the lachrymal (tear) system. That increase in fluid pushes out the tears.

2 - the more simplistic reason may be that when you yawn you scrunch up a bunch of facial muscles. That causes the tear glands and ducts to be squished, forcing out some tears.

Answer 2

This is something that happens to me too...I believe it is because I have no resistence to my feelings when I am that tired. Often I also get very silly, laugh and make goobery jokes when I am tired...I guess it all in the setting. Yesterday, Friday, when I am already tired from a long week...Iwas watching miracle pets in the morning...they showed a dog who missed it owner and ran away to find where it use to live...it made me think of a dog I had and his sad story and I just started bawling...it kinda set the day ...i think its normal and nothing to worry about. So smile anyway.

Answer 3

we don't generally cry when we are tired. our eyes do turn red though due to blood vessel dilatation and increased retention of the secondary metabolites due the consequent sluggish flow of blood. this causes our eyes to burn which may be mistaken for the 'stinging' sensation when we cry.