Resonance phenomena is present and have been studied in a large variety of systems going from physical, chemical to biophysical systems. In this talk I will present two resonance phenomena. The first one occurs in the motor system, in particular, in motoneurons related to the monosynaptic reflexes elicited by periodic electrical stimulation in presence of mechanical noise. Our experimental and numerical results provide the first direct demostration that the motor system, and not only the sensory system, exhibit the stochastic resonance phenomenon. The second resonance behavior is related to the presence of diversity in an ensamble of excitable units. We study the effect of diversity in a system of neurons whose dynamical behaviour is described by the Morris-Lecar model. When such system is subjected to an external subthreshold signal, we observe that their response is optimized for an intermediate value of the diversity. We also observe a resonant response of the system to a certain period of the external signal. These results show that intrinsic diversity might have a constructive role and suggest that natural systems might profit from their diversity in order to optimize the response to an external stimulus.