When you sneeze, the pressure inside your nose increases. This causes a reflex contraction of the abdominal muscles that push air and particles out of your nose. The flow of air is controlled by two muscles in your neck – the sterno-scapular (upper) muscle and the scalene (lower) muscle. These muscles attach to the vertebrae directly below your Adam’s apple.
At the same time, a nerve impulse travels from the brain to the mucous membranes lining your nasal passages. These nerves signal surrounding muscles to contract, which directs expulsion of air and fluid from your nasal passage.