Final answer:
Acetylcholine (ACh) is the most abundant neurotransmitter in the human body, playing a crucial role in muscle activation and various nervous system functions.
Step-by-step explanation:
The most abundant neurotransmitter in the human body, often abbreviated as ACh, is Acetylcholine. Acetylcholine is an organic chemical that functions as a neurotransmitter, which nerve cells release to send signals to other cells. Its role is pivotal in both the peripheral nervous system (PNS) and central nervous system (CNS). In the PNS, acetylcholine activates muscles at the motor end-plate to trigger depolarization. In the CNS, it is involved in a myriad of functions, including the autonomic nervous system where it acts as a neurotransmitter in the sympathetic nervous system and as the final product released by the parasympathetic nervous system. Anticholinergics are substances that interfere with acetylcholine activity and can have effects ranging from paralysis to convulsions.