Coronary pressor reflexes.

The heart differs from other cardiovascular reflexogenic structures because it has two prominent inputs to the central nervous system. On input is spinal and is mediated by afferent cardiac sympathetic nerve fibers. The other is medullary and is mediated by afferent vagal fibers. The number of fibers projecting centrally appears to be similar in the two systems. The reflex effects produced by excitation of the two inputs are complicated and can be either pressor or depressor. However, reflex pressor effects seem to be more prominant for the spinal input and reflex depressor effects more prominent for the medullary input.