Which response does NOT occur when the parasympathetic nervous system is activated?

When the parasympathetic nervous system is activated, it promotes a state of rest and relaxation within the body, often referred to as the "rest and digest" response. This activation typically results in several physiological responses aimed at conserving energy and facilitating digestion.

Dilation of pupils and bronchi is not a response associated with the parasympathetic nervous system. Instead, this action is primarily mediated by the sympathetic nervous system, which prepares the body for "fight or flight" responses. When the sympathetic system is active, pupils dilate and bronchi widen to increase airflow and enhance vision in preparation for perceived danger.

In contrast, when the parasympathetic nervous system is engaged, heart rate and respiratory rate decrease, aiding in the body's shift toward a more restful state. Additionally, blood vessel dilation occurs to facilitate increased blood flow to the digestive organs, supporting effective digestion. Stimulation of the salivary glands corresponds with enhanced digestive processes, as increased saliva production aids in breaking down food.

Overall, the only response that is not characteristic of parasympathetic activation is the dilation of pupils and bronchi, which is aligned with the sympathetic response.