5.1: Introduction

The development of the nervous system is a complex and intricately coordinated process spanning multiple stages, from the early embryonic stages through childhood, adolescence, and adulthood. During early developmental stages, the brain becomes able to dynamically transfer information across billions of interconnected neurons, and coordinate and control mental and bodily functions, including perception, cognition, and movement.

Psychologists study genetics in order to better understand the biological factors that contribute to certain behaviors, thoughts, and feelings. Our genes provide a “blue-print” for making the proteins that are the building blocks of our bodies, including our nervous system. Understanding genetics helps us to answer questions like:  How are genetic diseases passed through family lines? Are there genetic components to psychological disorders such as depression or schizophrenia?

In this chapter, we first take a look at how we inherit our genes and how they can affect our appearance, our minds and behavior. We then cover the stages of nervous system and brain development in humans. We examine prenatal and postnatal stages of development from embryo through old age. We will also cover different stages of neuronal development, including neuron growth, migration, and death, as well as adult neurogenesis. Lastly, we will examine neuroplasticity—the brain’s ability to reorganize in response to intrinsic or extrinsic experiences—and how neuroplasticity is strongest during sensitive and critical periods of development. Learning how the nervous system develops and changes across the lifespan provides a more complete understanding of the brain.