The post-ganglionic nerve fibres of sympathetic. nervous system are adrenergic i.e., they release the neurotransmitter. nor-adrenaline at their termination. The sympathatic nerves stimulate the adrenal glands to secrete adrenaline. The post- ganglionic para-sympathatic fibers are cholinergic i.e., they release a chemical substance acetyl choline, a neurotransmitter, at their endings for the transmission of nerve empulses.