Which type of effect is typically produced by a receptor limited to a specific tissue region when activated?

Which type of effect is typically produced by a receptor limited to a specific tissue region when activated?

• A. No effect
• B. Localized effect
• C. Widespread effect
• D. Variable effect

Answer: (B)

When a receptor is confined to a specific tissue region, activating it produces changes only in that region. The drug can initiate signaling only where the receptor is expressed, so other tissues that lack the receptor don’t respond. This makes the effect localized to the tissue where the receptor resides. If the receptor were widespread, you'd expect a widespread effect; if there were no functional receptor, there would be no effect at all. A variable effect could occur with differences in receptor density or sensitivity, but the defining outcome for a tissue-restricted receptor is a localized effect.

When a receptor is confined to a specific tissue region, activating it produces changes only in that region. The drug can initiate signaling only where the receptor is expressed, so other tissues that lack the receptor don’t respond. This makes the effect localized to the tissue where the receptor resides. If the receptor were widespread, you'd expect a widespread effect; if there were no functional receptor, there would be no effect at all. A variable effect could occur with differences in receptor density or sensitivity, but the defining outcome for a tissue-restricted receptor is a localized effect.