<P> There are two kinds of neurons involved in the transmission of any signal through the sympathetic system: pre-ganglionic and post-ganglionic . The shorter preganglionic neurons originate from the thoracolumbar region of the spinal cord specifically at T1 to L2 ~ L3, and travel to a ganglion, often one of the paravertebral ganglia, where they synapse with a postganglionic neuron . From there, the long postganglionic neurons extend across most of the body . </P> <P> At the synapses within the ganglia, preganglionic neurons release acetylcholine, a neurotransmitter that activates nicotinic acetylcholine receptors on postganglionic neurons . In response to this stimulus, the postganglionic neurons release norepinephrine, which activates adrenergic receptors that are present on the peripheral target tissues . The activation of target tissue receptors causes the effects associated with the sympathetic system . However, there are three important exceptions: </P> <Ol> <Li> Postganglionic neurons of sweat glands and chromaffin cells of the adrenal medulla . Postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors, except for areas of thick skin, the palms and the plantar surfaces of the feet, where norepinephrine is released and acts on adrenergic receptors . </Li> <Li> Chromaffin cells of the adrenal medulla are analogous to post-ganglionic neurons; the adrenal medulla develops in tandem with the sympathetic nervous system and acts as a modified sympathetic ganglion . Within this endocrine gland, pre-ganglionic neurons synapse with chromaffin cells, triggering the release of two transmitters: a small proportion of norepinephrine, and more substantially, epinephrine . The synthesis and release of epinephrine as opposed to norepinephrine is another distinguishing feature of chromaffin cells compared to postganglionic sympathetic neurons . </Li> <Li> Postganglionic sympathetic nerves terminating in the kidney release dopamine, which acts on dopamine D1 receptors of blood vessels to control how much blood the kidney filters . Dopamine is the immediate metabolic precursor to norepinephrine, but is nonetheless a distinct signaling molecule . </Li> </Ol> <Li> Postganglionic neurons of sweat glands and chromaffin cells of the adrenal medulla . Postganglionic neurons of sweat glands release acetylcholine for the activation of muscarinic receptors, except for areas of thick skin, the palms and the plantar surfaces of the feet, where norepinephrine is released and acts on adrenergic receptors . </Li>

Is epinephrine part of the sympathetic nervous system