The great diversity of neuronal nAChRs equips them for many roles. The broad, diffuse projections of the cholinergic system and their influence on multiple neurotransmitter systems enable nAChRs to have a wide modulatory influence on excitability on multiple time scales. Both excitatory and inhibitory synapses are directly modulated by nAChR activity. Although fast nicotinic transmission is not a major excitatory drive, it may alter the excitability of many synapses at one time. Depending on the neural area and stage of development, nAChRs of multiple subtypes will have varying degrees of importance in regulating neuronal excitability.