This is the second in a series of presentations on the interrelationships between energy metabolism, brain function and resilience, and disease processes. In this episode I describe how mitochondria are moved about within axons and dendrites, how mitochondria divide, fuse with each other, and are eliminated when they become dysfunctional. Importantly, mitochondria influence and respond to activity in neuronal networks in ways that optimize energy efficiency and promote the formation and maintenance of synapses between neurons. I also introduce the next presentation which will focus on how physical exercise and intermittent fasting affect brain function, plasticity, and resilience.