This review from 2004 describes the importance of copper homeostasis as excess and deficiency have significant adverse effects on the body and particularly on the nervous system.
Authors demonstrated that in copper deficiency, mitochondrial function is impaired due to decreased activity of cytochrome c oxidase, leading to production of reactive oxygen species, which in turn triggers mitochondria-mediated apoptotic neurodegeneration.
Rossi L, Lombardo MF, Ciriolo MR, Rotilio G. Mitochondrial dysfunction in neurodegenerative diseases associated with copper imbalance. Neurochem Res. 2004 Mar;29(3):493-504. doi: 10.1023/b:nere.0000014820.99232.8a. PMID: 15038597.