This chapter delves into the complexities of the nervous system, covering a wide range of diseases, structural anomalies, and tumors that affect the central and peripheral nervous systems. Conditions such as Alzheimer disease, amyotrophic lateral sclerosis (ALS), and Parkinson’s disease are discussed, with a focus on their pathophysiology, clinical manifestations, and diagnostic methods. The chapter also addresses congenital disorders such as holoprosencephaly and anencephaly, exploring their causes and the impact on neurodevelopment. Intracranial pathologies such as cerebral abscesses, hemorrhages, and hydrocephalus are explored in detail, with discussions on mechanisms such as anoxia and infarction. It highlights various tumors, including glioblastomas, astrocytomas, and medulloblastomas, and their cellular characteristics. Neuroinflammatory diseases such as meningitis and conditions such as dementia and Tay-Sachs disease are also covered. The chapter provides valuable insights into the structural and functional impairments of the nervous system, supporting clinical understanding and diagnosis of these critical conditions.