Nociceptors are activated by which stimuli?

• A. Thermal and chemical stimuli
• B. Mechanical, thermal, and chemical stimuli
• C. Mechanical stimuli only
• D. Electrical stimulation

Answer: (B)

Nociceptors are free nerve endings that detect noxious, potentially tissue-damaging stimuli to protect tissue. They respond to three main types of stimuli: mechanical forces (such as pressure, pinch, or crush), thermal extremes (extremely hot or cold that can cause injury), and chemical signals released during tissue damage or inflammation (like inflammatory mediators and irritants such as capsaicin). Because any of these can trigger nociceptor firing, the correct answer includes mechanical, thermal, and chemical stimuli. Electrical stimulation isn’t a typical natural trigger for nociceptors, and a choice limited to only one type misses the others.