What is the similarity between toxicity caused by an overdose of acetylcholine or nicotine and by the use of ganglionic blockers such as mecamylamine?

In neurology, postganglionic nerve fibers are autonomic nerve fibers from the ganglion to the effector organ. These, unlike preganglionic fibers (whose sole neurotransmitter is acetylcholine) have a variety of neurotransmitters to fulfill their functions.

Neurotransmitters

The neurotransmitters of postganglionic fibers are varied, and are distributed as follows:

In the parasympathetic nervous system, neurons are cholinergic (Acetylcholine is the primary neurotransmitter)

In the sympathetic nervous system, neurons are mostly adrenergic (norepinephrine-epinephrine and / or norepinephrine, both have the same chemical structure, but epinephrine has a methyl group unlike norepinephrine that has a hydrogen, instead of a methyl group - act as the primary neurotransmitter) Two exceptions to this are the sympathetic innervation of the sweat glands and the piloerector muscles where the neurotransmitter in both pre and post ganglionic synapses is acetylcholine and in the vessels of the renal cortex where dopamine is used as the main neurotransmitter. Another exception is the sympathetic innervation of the medulla of the adrenal gland, which is innervated by preganglionic fibers, and subsequently uses acetylcholine as a neurotransmitter. Adrenal medulla cells are, in fact, modified postganglionic neurons that secrete epinephrine and norepinephrine directly into the bloodstream rather than a synapse.

In both divisions of the autonomic nervous system, postganglionic neurons express nicotinic acetylcholine receptors to receive signals from preganglionic neurons.