Figure 1 summarizes the pathways discussed in this review. Noxious and innocuous cardiac and somatic information converge on SRT neurons in the upper thoracic spinal cord; the third thoracic segment (T3) is shown in Figure 1. The SRT pathway and collaterals of the STT convey this information to the MRF (mainly RGC). This input is integrated with other inputs (eg. auditory and visual) by MRF neurons, some of which project to the spinal cord. RS motor neurons (dotted pathway) might mediate motor responses to cardiac pain, as well as motor responses associated with escape or alerting behavior. RS neurons (cross-hatched and clear pathways) can also modulate ascending traffic by altering activity of SRT and STT cells. Finally, RS neurons (dotted pathway) might modify sympathetic function via collaterals to IML or to interneurons, or MRF cells could project to medullary areas possessing neurons (solid pathway) that project directly to IML. The small figurines represent the heart (top), blood vessels (middle right) and muscle (bottom).