Which organ system is associated with the acute radiation syndrome at doses greater than 5000 RAD?

• A. Central Nervous System
• B. Gastrointestinal System
• C. Hematopoietic System
• D. Skin

Answer: (A)

At very high radiation doses, the most lethal effects of acute radiation syndrome target the central nervous system. Once the dose exceeds about 50 Gy (5000 rad), damage to brain vessels and neural tissue leads to rapid neurological decline, cerebral edema, seizures, and death within a short time. Other ARS syndromes—hematopoietic and gastrointestinal—occur at lower dose ranges, so they dominate earlier, while the skin may show effects at different exposure levels. Thus, the central nervous system is the organ system most associated with ARS at doses above 5000 rad.