when I see you..

.. that's when my cornea catches the first glimpse of you. My retina absorbs the lights of you, turns them into impulses that run through my optical nerves to my brain. It stimulates my hypothalamus to secrete serotonines that makes me happy. That's when my sympathetic nerves activated; produces adrenalines that burst to my blood. It explains why my heart trembles and my pupils get wider. My fingers and my feet are chilled cause my blood vessels are got constricted.

Basically.. many things happened when I see you. You won't know cause the only visible response that I do when I see you is..
my seventh cranial nerve's got contracted-
so it puts smile. In my face.