What is the term for unlearned, unorganized, involuntary responses that occur automatically in the presence of certain stimuli?

The correct answer is reflexes.  

A reflex action, or reflex, refers to an involuntary and almost immediate motion in reaction to a stimulus. A reflex is made conceivable by neural pathways known as reflex arcs that can function on an impulse prior of the impulse reaching the brain. The reflex is thus an automatic reaction towards a stimulus, which does not need or receive cognizant thought.