That is, touching sugar elicits firing of sensory neurons, but their firing and the release of neurotransmitters does not affect the inhibition of leg movement or proboscis extension or feeding behavior. Divergence refers to the fact that one stimulus can affect many responses. A pinprick to a foot of a cat causes the leg to lift up. But, just as automatically, the three other legs adjust so that the cat doesn't fall over. The stimulus causes a pattern of responses.
Divergence means one cause, many effects.
Convergence refers to many different stimuli can cause the exact same response. In the context of this chapter, convergence is a way of understanding the chain of effect from external stimuli to internal factors all the way to the final response. A painful stimulus is followed by leg withdrawal. But, we can stimulate certain cells in the brain and get the same leg withdrawal response. We can even remove the brain and stimulate a part of the spinal cord and get the same response.