Nicotinic acetylcholine receptors (nAChRs) are receptor proteins that respond to the neurotransmitter acetylcholine and drugs like nicotine. They are found in the central and peripheral nervous system, muscle, and other tissues.
Here are some things to know about nAChRs: 

    Structure
    nAChRs are pentameric proteins that belong to the Cys-loop receptor superfamily. 

Function
When activated by acetylcholine or nicotine, nAChRs allow specific ions to flow across the cell membrane. 
Subtypes
There are many subtypes of nAChRs, including the a7 nAChR. The a7 nAChR is found in neuronal and non-neuronal cells, and is activated by acetylcholine to mediate the flow of Na,(sodium) K,(potassum) and Ca (calicum) ions. 
Nicotine binding
Nicotine acts as an agonist to nAChRs, meaning it mimics the effects of acetylcholine and binds to the receptors competitively. 
Signal transduction
The signal transduction process mediated by nAChRs is regulated by allosteric modulators, which bind to sites distinct from the neurotransmitter site and the ion channel.