Feedback and sensitivity are core concepts of control theory, but the theory is grounded in the frequency-domain analysis of open dynamical systems and mature only for linear time-invariant (LTI) systems. Excitability is a core concept of mathematical physiology, but the theory is grounded in the state-space analysis of closed dynamical systems, with little contact to control theory. This tutorial will review the three concepts, with the aim of connecting them to address the control and modulation of rhythmic behaviors encountered in biology. The emphasis will be on experimental questions of neurophysiology. This discipline benefits from a matured modeling framework grounded in circuit theory, a key historical bridge between input-output and state-space modeling.