Question at position 4 Olfactory (odor) receptors are chemoreceptors. TrueFalse

Question

Question at position 4 Olfactory (odor) receptors are chemoreceptors. TrueFalse

BlackTom AI · Accepted Answer

Olfactory receptors detect and transduce airborne chemical molecules (odorants) into neural signals, therefore they are chemoreceptors.

1. Relevant knowledge points and concepts
- Chemoreceptors respond to chemical stimuli (molecules or ions) and convert them into electrical signals.
- Olfactory receptors are specialized neurons in the olfactory epithelium that bind odorant molecules.
- Olfactory transduction uses G-protein–coupled receptor (GPCR) mechanisms and ionic changes to generate action potentials that travel to the olfactory bulb and cortex.

2. Step-by-step reasoning process
- Odorant molecules in the air enter the nasal cavity and dissolve in the mucus over the olfactory epithelium.
- An odorant binds to an olfactory receptor protein on the cilia of an olfactory sensory neuron. These receptor proteins are GPCRs (olfactory receptors).
- Binding activates the Golf G-protein, which stimulates adenylyl cyclase to convert ATP to cyclic AMP (cAMP).
- cAMP opens cyclic nucleotide-gated (CNG) ion channels, allowing Na+ and Ca2+ influx, producing receptor potential (depolarization).
- If depolarization reaches threshold, action potentials travel along the olfactory nerve to the olfactory bulb and onward to higher brain centers for odor perception.

3. Intermediate steps (molecular/transduction steps shown)
- Odorant + OR → OR* (activated receptor)
- OR* → activation of Golf
- Golf → adenylyl cyclase activation
- Adenylyl cyclase: ATP → cAMP (↑)
- cAMP → opens CNG channels → Na+/Ca2+ influx → depolarization → action potential

4. Why the correct answer is correct
- The sequence above is exactly the definition of chemoreception: a chemical stimulus (odorant) binds a receptor and is converted into an electrical nerve signal. Thus olfactory receptors meet all criteria for chemoreceptors.

5. Why the other option is incorrect
- "False" would imply olfactory receptors are not chemoreceptors. That contradicts anatomical and physiological evidence: olfactory receptors do not primarily sense light, pressure, temperature, or pain (photoreceptors, mechanoreceptors, thermoreceptors, nociceptors), but bind chemical odorants.

6. Conclusion
- Therefore the correct answer is True, which matches the provided answer.

Question at position 4 Olfactory (odor) receptors are chemoreceptors. TrueFalse单项选择题

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