In the same way the knee-jerk reflex is a thing (I think the nerve signal doesn't go through the brain?), can stimuli received by the eyes or ears trigger "instantaneous" (faster than the brain can process it) responses?
Short answer would be yes. There are very simple examples such as responses to sudden bright lights controlled in the Trigeminal nerve bundle to constrict pupils. Visual reflexes are interesting because it can frequently involve a neuron crossover in the nerve bundle. This would be an inappropriate reflex due to a stimuli. The most common being suddenly being exposed to a bright light causing you to sneeze like pepper was thrown in your face. Also interestingly this is an autosomal dominant trait so one of your parents will have to have the same response for you to inherite it. Photic sneeze response