Final answer:
The first fact about nervous system modulation is about the cholinergic system, which is based on acetylcholine and includes cholinergic synapses throughout the nervous system, especially in the autonomic nervous system divided into sympathetic and parasympathetic divisions.
Step-by-step explanation:
The first fact about nervous system modulation involves the cholinergic system, which is a neurotransmitter system based on acetylcholine. This system includes the neuromuscular junction (NMJ) as an example of a cholinergic synapse. Cholinergic synapses are not only found at the NMJ but are also widely distributed throughout the nervous system, including in the autonomic nervous system and various parts of the brain.
The autonomic nervous system is further divided into the sympathetic and parasythetic nervous systems. The sympathetic nervous system is typically activated in stressful situations, eliciting a "fight or flight" response. In contrast, the parasympathetic nervous system is more active during restful periods and is involved in maintaining normal bodily functions under relaxed conditions.