What are the two types of desensitization?

What are the two types of desensitization?

• A. Acute and chronic
• B. Homologous and heterologous
• C. Phosphorylation and internalization
• D. Upregulation and downregulation

Answer: (B)

Desensitization of receptors occurs when sustained stimulation leads to a reduced cellular response. The two main patterns are homologous desensitization and heterologous desensitization. Homologous desensitization means the receptor that was activated becomes less responsive, while other receptor types remain unchanged. This often happens through receptor-specific phosphorylation by GRKs and binding of arrestins, which uncouples the receptor from its G protein and can promote receptor internalization, diminishing signaling from that exact receptor. Heterologous desensitization occurs when activation of one receptor triggers signaling pathways that dampen the responsiveness of other, differently activated receptors. This happens via shared downstream kinases or second-messenger systems (like PKC or PKA) that can phosphorylate multiple receptor types, reducing signaling across several pathways even if those other receptors haven’t been directly stimulated. The other options don’t describe these two patterns: timing-focused terms (acute vs. chronic) describe duration rather than a receptor-specific vs. cross-receptor mechanism; phosphorylation and internalization are mechanisms involved in desensitization but aren’t the named categories themselves; upregulation and downregulation refer to changes in receptor numbers, not the functional desensitization patterns.

Desensitization of receptors occurs when sustained stimulation leads to a reduced cellular response. The two main patterns are homologous desensitization and heterologous desensitization.

Homologous desensitization means the receptor that was activated becomes less responsive, while other receptor types remain unchanged. This often happens through receptor-specific phosphorylation by GRKs and binding of arrestins, which uncouples the receptor from its G protein and can promote receptor internalization, diminishing signaling from that exact receptor.

Heterologous desensitization occurs when activation of one receptor triggers signaling pathways that dampen the responsiveness of other, differently activated receptors. This happens via shared downstream kinases or second-messenger systems (like PKC or PKA) that can phosphorylate multiple receptor types, reducing signaling across several pathways even if those other receptors haven’t been directly stimulated.

The other options don’t describe these two patterns: timing-focused terms (acute vs. chronic) describe duration rather than a receptor-specific vs. cross-receptor mechanism; phosphorylation and internalization are mechanisms involved in desensitization but aren’t the named categories themselves; upregulation and downregulation refer to changes in receptor numbers, not the functional desensitization patterns.