In the context of functional electrical stimulation (FES), it would be of great interest to get reliable sensitive information directly from the nerve signals. To achieve the chronic recording of electrical activity of the axons it is necessary to develop the electrode and the associated implantable integrated circuit ASIC. In this paper, we have proposed a novel design of multipolar cuff electrodes. This design is closely linked to a low-level analog signal processing assigned to a dedicated preamplifier. This paper presents the system-oriented development of this biosignal sensor, from the modeling of the neurons and the electrode to the microcircuit design. We put emphasis on the simulation of the action potential to assist the sensor specification.