What is the primary effect of nerve agents on the human body?

The primary effect of nerve agents on the human body is the disruption of the nervous system. Nerve agents, such as sarin or VX, function by inhibiting the enzyme that breaks down acetylcholine, a neurotransmitter responsible for transmitting signals in the nervous system. When this enzyme is blocked, acetylcholine accumulates at the synapses, leading to continuous stimulation of muscles, glands, and the central nervous system. This overwhelming stimulation can cause a range of symptoms, including muscle spasms, respiratory failure, and, in severe cases, death.

Understanding this mechanism highlights why the other choices are not as accurate. While nerve agents can indirectly affect respiratory function by causing muscle paralysis (including the muscles used for breathing), the main pathology occurs at the neurochemical level, which fundamentally disrupts essential nervous system functions. Severe burns are not associated with nerve agents; they typically result from thermal or chemical injuries. Depleting blood oxygen levels can occur over time due to respiratory distress caused by nerve agents, but it is not the primary effect. Therefore, the correct answer underscores the central role of the nervous system in the overall impact of nerve agents on human health.