The cholinergic system refers to the network of neurons that use the neurotransmitter acetylcholine to communicate. This system plays a crucial role in various functions, including muscle movement, memory, and attention. It is involved in both the central nervous system and the peripheral nervous system, influencing activities such as heart rate and digestion. In the brain, the cholinergic system is essential for cognitive processes, particularly in areas like the hippocampus and cortex. Dysfunction in this system is associated with several conditions, including Alzheimer's disease and other forms of dementia, highlighting its importance in maintaining cognitive health and overall brain function.