What is a common side effect of nerve agents like Sarin and related substances?

The correct answer highlights a critical aspect of the physiological response to nerve agents such as Sarin. Nerve agents function by inhibiting the enzyme acetylcholinesterase, leading to an accumulation of acetylcholine at synapses. This results in overstimulation of muscarinic and nicotinic receptors, causing a range of symptoms.

One of the hallmark effects of this overstimulation is a decreased heart rate, or bradycardia. This occurs due to excessive activity at the vagus nerve, which is part of the parasympathetic nervous system that slows heart rate. In contrast, normal physiological response to threats or stressors typically involves an increase in heart rate. The effects observed with nerve agents are paradoxical and distinctly differ from what one might expect in a fight-or-flight situation.

Additional symptoms of nerve agent exposure might include muscle twitching, confusion, and respiratory distress among others, demonstrating the systemic impact of these substances. However, the key connection to the impaired autonomic regulation reflects the profound decrease in heart rate occurring in response to these agents.