Which statement about Acetylcholine is true?

• A. Acts as the main inhibitory transmitter in the CNS.
• B. Is primarily found in the peripheral nervous system and is not involved in learning.
• C. Regulates appetite and mood.
• D. Is the primary transmitter used by efferent neurons carrying messages from the CNS, also involved in some kinds of learning and memory.

Answer: (D)

Acetylcholine serves as a key messenger for motor output from the CNS and also supports learning and memory within the brain. In the peripheral nervous system, it is the main transmitter used by motor neurons that innervate skeletal muscles, and it also acts as the preganglionic transmitter in both the sympathetic and parasympathetic divisions. In the brain, acetylcholine modulates attention, learning, and memory, with important roles in regions like the hippocampus and cortex. This combination of driving efferent CNS-to-body signals and contributing to cognitive processes makes the statement describing its primary role in efferent signaling from the CNS and its involvement in learning and memory the best fit.

As for the other ideas: acetylcholine is not the main inhibitory transmitter in the CNS (that’s GABA), and while it does influence mood and arousal, appetite and mood are more strongly linked to other neurotransmitter systems such as serotonin and dopamine.