1. A neural stimulation system for stimulating a nervous system including a sympathetic nerve and a parasympathetic nerve, the system comprising: a stimulation output circuit configured to deliver neural stimulation pulses; an autonomic balance monitoring circuit configured to sense one or more signals indicative of autonomic activities, the autonomic balance monitoring circuit including a heart sound sensing circuit configured to sense a heart sound signal of the one or more signals indicative of autonomic activities, the heart sound signal indicative of heart sounds; and a stimulation control circuit coupled to the stimulation output circuit and the autonomic balance monitoring circuit, the stimulation control circuit configured to control the delivery of the neural stimulation pulses using a plurality of stimulation parameters and including a stimulation parameter adjustment circuit configured to adjust the plurality of stimulation parameters using the one or more signals indicative of autonomic activities.