sympathetic part of autonomic division of nervous system

ra·mi communicantes of sympathetic part of autonomic division of nervous system

the communicating branches of the spinal nerves and sympathetic trunk, small bundles of nerve fibers connecting spinal nerves with sympathetic ganglia; the fibers passing from the ganglion to the spinal nerve are nonmyelinated and are called gray rami communicantes, those passing in the reverse direction are myelinated and are called white rami communicantes.