Cardiac vagal afferent nerves

The heart possesses a complex sensory innervation of mechanically and chemically sensitive endings that send action potentials to the central nervous system via vagal and sympathetic afferent pathways. These inputs impose reflex influences on sympathetic and parasympathetic outflow to control cardiac and hemodynamic function. In addition, sensory input is relayed to neurons in intrinsic cardiac ganglia that may serve a “local circuit” role in the coordination of parasympathetic and sympathetic activity to various regions of the heart. This chapter will discuss only the sensory innervation of the heart that sends impulses to the nucleus tractus solitarius in the medulla via the vagus nerves. This focus, however, is not intended to downplay the importance of cardiac sympathetic afferent neurons or sensory neurons in cardiac ganglia as components of an intricate sensory network that coordinates reflexes from the heart. The electrophysiology of sensory neurons in these other pathways has been summarized in other excellent reviews.^1-4.