Which statement about receptors in the autonomic nervous system is true?

Which statement about receptors in the autonomic nervous system is true?

• A. Receptors in the autonomic nervous system include both ionotropic and metabotropic types
• B. Only ionotropic receptors exist in the autonomic nervous system
• C. GPCRs are not involved in autonomic signaling
• D. All autonomic receptors are ion channels

Answer: (A)

In the autonomic nervous system, signaling uses two main receptor families: ligand-gated ion channels and G protein–coupled receptors. Nicotinic receptors, located in autonomic ganglia, are ionotropic channels that open when acetylcholine binds, producing fast depolarization. On the other hand, receptors on target organs, such as muscarinic receptors in the parasympathetic system and adrenergic receptors in the sympathetic system, are metabotropic GPCRs that signal through G proteins to drive slower, longer-lasting responses. This combination means autonomic signaling relies on both ionotropic and metabotropic receptors, making the statement true. The other options are inconsistent with what’s known: there are not only ionotropic receptors, GPCRs are involved, and not all autonomic receptors are ion channels.

In the autonomic nervous system, signaling uses two main receptor families: ligand-gated ion channels and G protein–coupled receptors. Nicotinic receptors, located in autonomic ganglia, are ionotropic channels that open when acetylcholine binds, producing fast depolarization. On the other hand, receptors on target organs, such as muscarinic receptors in the parasympathetic system and adrenergic receptors in the sympathetic system, are metabotropic GPCRs that signal through G proteins to drive slower, longer-lasting responses. This combination means autonomic signaling relies on both ionotropic and metabotropic receptors, making the statement true. The other options are inconsistent with what’s known: there are not only ionotropic receptors, GPCRs are involved, and not all autonomic receptors are ion channels.