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.)Multiple choice

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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）

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