  Limits on a system's response to external perturbations inform our
understanding of how physical properties can be shaped by microscopic
characteristics. Here, we derive constraints on the steady-state nonequilibrium
response of physical observables in terms of the topology of the microscopic
state space and the strength of thermodynamic driving. Notably, evaluation of
these limits requires no kinetic information beyond the state-space structure.
When applied to models of receptor binding, we find that sensitivity is bounded
by the steepness of a Hill function with a Hill coefficient enhanced by the
chemical driving beyond the structural equilibrium limit.
