The correct answer is b) excitatory.
Acetylcholine (ACh) is a neurotransmitter that plays a crucial role in transmitting signals in the nervous system. When ACh binds to nicotinic receptors, which are a type of acetylcholine receptor, it typically leads to an excitatory response. This is primarily because nicotinic receptors are ionotropic receptors that form ion channels. When acetylcholine attaches to these receptors, it causes a change in the receptor’s conformation, leading to the opening of the ion channel.
Once the channel is open, it allows for the influx of cations, such as sodium ions (Na+), into the cell. This influx depolarizes the postsynaptic membrane, raising the likelihood of an action potential firing. Therefore, the predominant response of nicotinic receptors upon binding with acetylcholine is excitatory in nature.