Master the Biology Bash: 2025 MCAT Biological Systems Practice Challenge!

In the context of brain anatomy, the term "cities" refers to the densely packed structure of grey matter. Grey matter primarily consists of neuronal cell bodies, dendrites, and unmyelinated axons, which together create a network of connections that enables complex information processing. This dense arrangement of neuronal bodies is crucial for functions such as cognition, sensation, and muscle control.

Grey matter typically forms the outer layer of the cerebral cortex and makes up key areas within different regions of the brain, including the nuclei of the basal ganglia and the thalamus. Its density contributes to the brain's capacity to process and integrate sensory information, as well as to execute higher-order brain functions.

In contrast, white matter, which is composed mainly of myelinated axons, facilitates communication between different regions of grey matter. It is generally lighter in appearance and connects various brain areas rather than containing the dense cell bodies seen in grey matter. The distinctions in structure and function between these two types of brain matter highlight why grey matter is often described in terms reflecting its dense and interconnected nature.