What type of neurotransmitter is primarily excitatory?

Acetylcholine is primarily considered an excitatory neurotransmitter because it plays a crucial role in transmitting signals across synapses, particularly in the autonomic nervous system and at neuromuscular junctions. When acetylcholine is released, it binds to its receptors on the postsynaptic neuron or muscle cell, leading to depolarization and the initiation of an action potential. This excitatory effect is vital for muscle contraction and various autonomic functions.

While norepinephrine, dopamine, and serotonin can have excitatory effects under certain conditions, they are often associated with modulatory roles in mood, arousal, and other complex neurophysiological processes. Acetylcholine's direct role in triggering muscle contraction and its significance in both central and peripheral nervous system signaling make it the primary excitatory neurotransmitter in these contexts.