NO its the light that stimulates the hen to lay in regular cycles.. but you have to be careful because if they get to much light it may turn into a pecking problem. You will read a lot that a red light is better to reduce pecking problems
and I have read on here before that if dont allow them to have a natural cycle it will shorten their laying life... meaning they will burn out faster
eta: when you say heat lamp... what colour is the bulb? red or white?
I use a light and I'm getting quite a few eggs even in mid-winter. I do notice that when it gets really cold (below 10 degees), I am getting fewer eggs despite the light.
I used a heat lamp for my first winter with them.... and it was fine... some of my hens just started molting in sept and the last of them are just finishing up now ... I have 17 raging from 1 year to 18 months