WordNet sense 1 (an area that is approximately central within some larger region):

center, eye, heart, middle

WordNet sense 2 (a point equidistant from the ends of a line or the extremities of a figure):

midpoint

WordNet sense 3 (a cluster of nerve cells governing a specific bodily process):

nerve center, nerve centre

WordNet sense 4 (direct one's attention on something):

concentrate, focus, pore, rivet