What activates olfactory receptors?

What activates olfactory receptors?

• A. Odorant molecules binding to proteins that transport them to olfactory dendrites.
• B. Sound waves vibrating the tympanic membrane.
• C. Light photons exciting photopigments in retina.
• D. Odorant molecules diffusing through blood to neurons.

Answer: (A)

Activation of olfactory receptors starts when odorant molecules in the nasal mucus are captured and delivered to the olfactory receptor neurons. Odorant-binding proteins bind these molecules and shuttle them to the receptors located on the dendritic membranes of the olfactory neurons. When the odorant binds its receptor, a signaling cascade is triggered that leads to depolarization and the electrical signal that conveys smell to the brain. This delivery-and-binding sequence is the initiating step for olfactory signaling, so the option describing odorants binding to proteins that transport them to the olfactory dendrites best fits how smell is detected. The other options describe processes related to hearing, vision, or systemic transport, which do not explain olfactory receptor activation.

Activation of olfactory receptors starts when odorant molecules in the nasal mucus are captured and delivered to the olfactory receptor neurons. Odorant-binding proteins bind these molecules and shuttle them to the receptors located on the dendritic membranes of the olfactory neurons. When the odorant binds its receptor, a signaling cascade is triggered that leads to depolarization and the electrical signal that conveys smell to the brain. This delivery-and-binding sequence is the initiating step for olfactory signaling, so the option describing odorants binding to proteins that transport them to the olfactory dendrites best fits how smell is detected. The other options describe processes related to hearing, vision, or systemic transport, which do not explain olfactory receptor activation.