What is the primary neurotransmitter of the sympathetic nervous system?

What is the primary neurotransmitter of the sympathetic nervous system?

• A. Norepinephrine
• B. Acetylcholine
• C. Dopamine
• D. Epinephrine

Answer: (A)

Norepinephrine is the primary chemical signal released by postganglionic sympathetic neurons onto target organs, where it binds adrenergic receptors to produce the characteristic fight-or-flight responses. The preganglionic neurons in this pathway release acetylcholine to activate the postganglionic neuron, but the actual transmission to the organ is mainly via norepinephrine. Epinephrine released from the adrenal medulla acts as a circulating hormone that enhances these effects systemically, but it isn’t the usual neurotransmitter at sympathetic synapses. Dopamine isn’t the main transmitter in this system, and acetylcholine is used at the preganglionic synapse and at a few specific endings (like sweat glands), not as the primary signal at most sympathetic targets.

Norepinephrine is the primary chemical signal released by postganglionic sympathetic neurons onto target organs, where it binds adrenergic receptors to produce the characteristic fight-or-flight responses. The preganglionic neurons in this pathway release acetylcholine to activate the postganglionic neuron, but the actual transmission to the organ is mainly via norepinephrine. Epinephrine released from the adrenal medulla acts as a circulating hormone that enhances these effects systemically, but it isn’t the usual neurotransmitter at sympathetic synapses. Dopamine isn’t the main transmitter in this system, and acetylcholine is used at the preganglionic synapse and at a few specific endings (like sweat glands), not as the primary signal at most sympathetic targets.