One group of drugs retards heart rate, promotes digestion, contracts the eye pupil, etc. The other group has the opposite effect. These drugs are affecting the

A) motor and sensory nerves.
B) cerebrum and cerebellum, respectively.
C) central and peripheral nervous systems.
D) neurostimulatory and neuroinhibitory synapses.
E) sympathetic and parasympathetic nervous systems.

The two groups of drugs described are affecting the sympathetic and parasympathetic nervous systems, respectively. The first group of drugs described as retarding heart rate, promoting digestion, and contracting the eye pupil are characteristic effects of the parasympathetic nervous system. In contrast, the second group of drugs that have the opposite effects are more in line with the actions of the sympathetic nervous system. Therefore, the best choice is E, which is the sympathetic and parasympathetic nervous systems.