十万个为什么·科学启蒙30篇（4）

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为什么打喷嚏会闭眼

Sneezing is a powerful reflex triggered by irritation in the nasal passages or throat.
Nerves in the nose send signals to the brainstem, which coordinates multiple muscle groups simultaneously.
One automatic response is tightening the eyelid muscles, causing eyes to shut tightly without conscious control.
This protective action helps prevent irritants, mucus, or tiny particles from entering the eyes during the explosive exhale.
The force of a sneeze can exceed 100 miles per hour, making eye protection especially important.
Even people who try to keep their eyes open usually cannot override this hardwired reflex.
Scientists believe blinking during a sneeze may also stabilize head position for better respiratory efficiency.
The entire sequence—from trigger to eye closure—takes less than half a second.
It is not caused by air pressure pushing the eyes shut, as some myths claim.
This reflex highlights how closely linked our sensory and motor systems are for survival.