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Fasciculation refers to the spontaneous, involuntary contraction of muscle fibers, which can often be visually perceived as twitching. The phenomenon is directly linked to the depolarization of the muscle cell membranes. When succinylcholine, a neuromuscular blocker commonly used during anesthesia, is administered, it mimics acetylcholine by binding to the nicotinic receptors at the neuromuscular junction. This binding leads to the depolarization of the muscle membrane, resulting in muscle contractions. These contractions manifest as fasciculations and are transient, occurring before the muscle becomes paralyzed due to continued receptor occupation by succinylcholine.

The other options do not accurately describe fasciculation: a rapid heartbeat pertains to cardiovascular responses, increased neurotransmitter release at synapses does not directly lead to fasciculation, and mild spasms from dehydration relate to different muscle responses. Thus, the phenomenon of fasciculation is specifically tied to the effects of succinylcholine and the depolarization process in skeletal muscles.