"then who is cooling the north-south poles?"
This is the wrong question, it should read who or what is heating up the rest. If there were no sources of heat in the Universe, the temperature would be minus 273°C or Absolute $0$! Anywhere that is not getting infra red radiation would tend to this temperature i.e. planets that only show one side to the Sun.
If you measure the amount of infra red radiation falling of a square metre of the Arctic you would find that it is considerably less than that falling on a square metre between the Tropics. Add to this, the fact that both Arctic and Antarctic, due to being white, are reflecting a large part of this energy back into Space.
Absorbing heat radiation is very important, especially for Polar Bears, which despite appearing white actually have dark skin and fur that is black. The fur that we can see only appears white, it is in fact transparent to allow absorption of heat radiation.