How Neurons Work

Abstract This chapter provides an overview of how the brain’s approximately 86,000,000,000 neurons communicate with each other through a process known as synaptic transmission. The chapter reviews how neurons communicate both chemically and electrically, and discusses how human behavior arises from the complexity of these neuronal connections and interactions. The chapter also explains how nerve impulse transmission is improved by a substance called myelin, which is impaired in diseases like multiple sclerosis. The chapter discusses legally relevant aspects of brain development, including how early life adversity can affect connections between neurons, the extent to which plasticity (the ability of the brain to modify its connections) continues throughout the lifespan for different circuits, and the extent to which plasticity depends on critical periods (the limited period in which a given brain development may occur) and sensitive periods (when development is more easily achieved). The chapter concludes with brief descriptions of the major functions of four key neurotransmitters: dopamine, serotonin, norepinephrine, and oxytocin.