I was wondering if the cell cycle occurs constantly and only speeds up or slows down or can it come to a complete hault? My science teacher claims it can come to a complete halt when cells such as skin cells come in contact with other cells because of external regulators.

 

 

thanks

Yeah, you have the four main phases of the cell cycle, G1, S, G2, and M. There's another stage called G0 that cell will enter if it recieves signals telling it not to divide during the G1 phase. The cell can re-enter the G1 phase though, if it gets the right signals. So neurons from a brain, which are in the G0 phase, can be cultured in growth hormones and will re-enter the cell cycle.