Which of the following statements are true of olfactory sensory neurons? (Select all that apply.)

Question

BlackTom AI · Accepted Answer

Olfactory sensory neurons transduce odorants via G-protein–coupled receptor signaling that raises cAMP and opens cyclic-nucleotide–gated (CNG) cation channels, causing depolarization.

1) Relevant knowledge points and concepts
- Olfactory receptors are GPCRs that activate the G-protein Golf and adenylyl cyclase III, producing cAMP.
- cAMP directly opens CNG channels in the OSN cilia, permitting Na+ and Ca2+ influx; Ca2+ also activates Ca2+-gated Cl– channels, amplifying depolarization.
- OSN axons traverse the cribriform plate to the olfactory bulb and converge on glomeruli, where they synapse primarily onto mitral and tufted cells; interneurons in the glomerular/ external plexiform layers include periglomerular and granule cells with different roles.
- Each mature OSN typically expresses one odorant receptor gene, but each receptor is broadly tuned and can respond to multiple odorants (combinatorial coding).

2) Step-by-step reasoning
- Odorant binds receptor → Golf activated → adenylyl cyclase III increases cAMP → cAMP binds/opens CNG channels → Na+ and Ca2+ influx → membrane depolarization (with Cl– efflux amplifying response).
- Anatomically, OSN axons pass through the cribriform plate and target specific glomeruli based on receptor identity, not simply the nearest glomerulus.
- Within glomeruli, primary synapses are onto mitral/tufted cell dendrites; granule cells do not receive direct OSN input (they interact with mitral cells via dendrodendritic synapses deeper in the bulb).
- Odor coding is combinatorial: one receptor can respond to multiple odorants and one odorant can activate many receptors.

3) Why the correct answer is correct
- The statement that odorant-initiated depolarization is due to activation of a cyclic nucleotide–gated cation channel is consistent with the established cAMP→CNG channel mechanism.

4) Why other options are incorrect
- OSNs do not synapse with granule cells in glomeruli; they synapse onto mitral/tufted cells and periglomerular cells.
- Each odorant receptor is not exclusive to a single odorant; receptors are broadly tuned (combinatorial coding).
- OSN axons do project through the cribriform plate but do not simply synapse in the closest glomerulus; they converge on specific glomeruli determined by receptor type.

Conclusion: The correct selection is the statement about CNG channel–mediated depolarization, matching the provided answer.

Which of the following statements are true of olfactory sensory neurons? (Select all that apply.)多项选择题

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Which of the following statements are true of olfactory sensory neurons? (Select all that apply.) 以下关于嗅觉感觉神经元的描述哪些是正确的？（可多选）

Question at position 24 What triggers the depolarization of an olfactory receptor cell?Transport of odorant molecules into the cytoplasmInflux of sodium and calcium ionsEfflux of potassium ions from the cellBinding of neurotransmitters to post-synaptic receptorsConversion of GTP into GDP

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