10.1: Introduction

The complexity and capabilities of a well-functioning human brain are truly astonishing. The three-pound mass of molecules is organized in an intricate web of billions of neurons and support cells. These interconnected neural networks coordinate to control our most mundane functions and our most profound thoughts. The distributed patterns of brain activity enable us to perceive, learn, experience, create, communicate, empathize, and dream, propelling our species toward unending innovation and discovery. Yet, for all its capabilities and general resilience, the brain remains vulnerable.

The delicate balance in a well-functioning brain can be disrupted in many ways causing various dysfunctions. Brain cells need oxygen and nutrients to survive–interrupted supply can be devastating. Neurons use neurotransmitters to communicate–too little or too much can stop communication or kill cells. Brain cells are fragile and are easily damaged by force or by invading agents. Proteins can build up and disrupt function. Brain cells can die and cause atrophy.

This chapter delves into the darker side of brain biology: brain damage and neurodegeneration. We will explore how things can go awry in this intricate organ and lead to serious alterations in behavior, cognition, and quality of life. Understanding these aspects is not only crucial for appreciating the brain’s fragility but also for developing effective therapies for the many types of brain damage and neurodegeneration.

Brain damage can occur in many ways, including traumatic brain injury, tumor, stroke, encephalitis (inflammation of the brain often caused by infections), hydrocephalus (fluid buildup inside the skull that increases pressure), lack of oxygen, and meningitis (inflammation of the meninges, the protective membrane around the brain, usually caused by infection). In this section, we’ll go into detail about three of the most common types of brain damage: brain tumor, stroke, and traumatic brain injury (TBI). With TBI, we focus on an under-recognized epidemic–TBI that stems from intimate partner violence.

There are also many forms of neurological diseases and neurodegeneration. In this chapter, we’ll cover three common ones–Parkinson’s disease, Alzheimer’s disease, and Multiple Sclerosis.