Think globally, act locally
In order for a cell to move, it needs to choose a direction. How does the cell make the decision about which way to go? If the cell is in a gradient of attractant, it needs to become “polarized” in order to make a leading edge so it can move up the gradient toward the source.
But the problem is that there’s not much of a difference in concentration at the front and the back. The cell “amplifies” the small differences between the front and the back to become polarized. How do you amplify small differences?
One answer might be “local activation, global inhibition.” More on this later
