This chapter provides a comprehensive overview of neurons, the fundamental units of the central nervous system (CNS). It explores their morphology, classifications, and critical roles in anesthesia and pain regulation. The chapter discusses the structure of neurons, including soma, dendrites, and axons, and elaborates on synaptic transmission through chemical and electrical synapses. Key insights into synaptic plasticity, its implications for pain modulation, and its relevance to anesthesia are provided. Additionally, the chapter examines neural circuits involved in general anesthesia, pain perception, and reward mechanisms, highlighting their complexity and functional integration. The discussion underscores the significance of neurons in CNS functionality and their central role in both anesthesia and pain management.