Re: What is the excact pulse that makes cell divide?

This is from Molecular Biology of the Cell, third edition,Albert,Bray,Lewis
Raff, Roberts and Watson, Garland Pub.Inc.,1994

Protiens called growth factors are responsible for cell division.
Cells have receptor sites on their surfaces for a specific growth factor.
Once a transmembrane receptor receives its growth factor, the inner part
begins a cascade of signals which stimulates gene duplications and cell
division.

"At the molecular level M phase is initiated by a cascade of protien 
phophorylations triggered by the activation of the mitosis-inducing kinase
MPF,..."