Justine took a sip of milk and immediately spat it out because she realized it had soured. which path did messages in her nervous system follow to cause this reaction? sensory neurons → sensory receptors → motor neurons → interneurons sensory receptors → sensory neurons → interneurons → motor neurons motor receptors → interneurons → sensory neurons → sensory receptors sensory receptor → interneurons → sensory neuron → motor neurons

The answer is sensory receptors → sensory neurons → interneurons → motor neurons.  Justine took a sip of milk and immediately spat it out because she realized it had soured. The path of the messages is  sensory receptors → sensory neurons → interneurons → motor neurons, in her nervous system which cause this reaction.  
Sensory Receptor is that part of the nervous system that responds to stimuli
Sensory Neuron is that type of neuron that carries messages from special receptors to the central nervous system
Interneuron is the type of neuron that connects sensory and motor neurons
Motor Neuron is the type of neuron that carries messages from the central nervous system to effectors

The reaction will shift to the right