Which ARS subsystem has a threshold of about 10 Gy (1000 rad)?

• A. Hematopoietic
• B. Cardiovascular
• C. Genito-urinary
• D. Gastrointestinal

Answer: (D)

A dose around 10 Gy primarily triggers the gastrointestinal component of ARS because it directly damages the rapidly renewing cells lining the gut. When these intestinal crypt cells die, the mucosal barrier breaks down, leading to massive fluid and electrolyte loss, poor nutrient absorption, and a high risk of sepsis from bacterial translocation. Without intensive supportive care, this GI damage progresses quickly and can be fatal within about one to two weeks.

Lower doses tend to suppress the bone marrow, producing hematopoietic syndrome, while much higher doses are needed to cause cardiovascular collapse. Genitourinary effects aren’t the defining acute threshold at this level, so the 10 Gy mark best aligns with gastrointestinal failure.