Why do we open our mouths when shocked/ suprised etc?

Question

Why do we open our mouths when shocked/ suprised etc?

Answer 1

well you do as its lea rd behaviour

Answer 2

Its a reflex so that we can take in more oxygen just in case we need sudden physical strength or muscle use.

Answer 3

Gasp of air to fuel our muscles if we need to suddenly sprint out of danger.

Answer 4

It's a type of adrenalin, we take a quick intake of air into our lungs so we have a boost of energy to run/fight and things like that. It's for our own survival.

Except when you're shocked if you find out something like "Cassie has dumped David for Clare" type thing....

When people open their mouths for stuff like that, it's just to show that they're feeling shocked, but we don't get the adrenalin boost =P