The central nervous system syndrome occurs after a whole body dose of how many Gy or more?

The correct answer is 50 Gy or more because central nervous system (CNS) syndrome occurs at very high doses of radiation, typically around this threshold. At doses of approximately 50 Gy and above, the severe effects on the brain and spinal cord become evident, leading to a rapid onset of symptoms such as nausea, vomiting, confusion, and neurological impairments due to the destruction of sensitive neural tissues.

Doses lower than this, while still harmful, generally lead to other types of radiation syndromes, such as bone marrow syndrome or gastrointestinal syndrome, which manifest with different clinical symptoms and over different timelines. The CNS is particularly vulnerable due to the high metabolic demand of its cells and the limited capacity for regeneration compared to other tissues. This distinction is critical when discussing the biological effects of radiation exposure at various dose levels.