A. The duration of the stimulation

B. The location of the stimulation

C. The membrane potential at the site of stimulation

D. None of the above

I think the answer is B, because when the nociceptor is stimulated it relays information to the brain regarding location. Is this also true about stimuli below threshold?

  • $\begingroup$ What does "below threshold" mean to you? $\endgroup$ Mar 26 '17 at 18:25
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    – animuson
    Nov 20 '18 at 17:24
  • $\begingroup$ @animuson can you explain this deletion further? It was a reasonably well received Q with a equally appreciated answer? What is SimBio? $\endgroup$
    – AliceD
    Nov 20 '18 at 22:04
  • $\begingroup$ @AliceD SimBio was the company that claimed copyright over the text and demanded it be taken down. Read here for more info on the policy: meta.stackexchange.com/questions/317709/… - It had nothing to do with question quality. We were legally required to remove it. $\endgroup$
    – animuson
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  • $\begingroup$ @animuson - thanks for explaining - but which text? The question seems a general textbook question, and the answer (i.e., my answer) only cites a genuine research paper and wikipedia? How can that be copyrighted? $\endgroup$
    – AliceD
    Nov 21 '18 at 18:51

Short answer

Nociceptors are free nerve endings, and usually consist of bundles of unmyelinated fibers (Messlinger, 1997).

So nociceptors are basically axonal fibers. Below threshold, activation of these fibers do not cause action potentials to occur. Since action potentials are, basically, all-or-nothing events no signals will be sent to the brain. Hence, the brain will not receive information on either duration (A), or location (B) of the pain stimulus. The membrane potential (C) is a non-sense answer. Membrane potential, although it may affect receptor response properties, is never the primary message of a receptor signal. It is about the sensation of physical stimuli (in this case painful mechanical, heat or chemical stimuli).

So the answer is -D- as we have disputed A, B and C.

When receptors convey graded potentials, the term 'below-threshold' doesn't really apply anymore. Graded potentials can, in principle, convey the smallest stimulus difference as they operate on an analogue scale. Therefore, this question targets your understanding of the binary nature of action potentials and their threshold, and what that means for the detection of below-threshold stimuli.

- Messlinger, Anaesthesist (1997); 46(2): 142-53


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