Final answer:
Dr. Tanner's observation likely involved pesticide exposure causing damage to the hair cells in the organ of Corti, inhibiting their ability to bend and consequently disrupt auditory function. The correct option is d. Pesticide exposure caused damage to hair cells, preventing them from bending in response to sound.
Step-by-step explanation:
Based on the information provided, Dr. Tanner is studying the impact of pesticide exposure on the auditory function in a rodent model. The organ of Corti is essential for hearing as it contains hair cells responsible for converting sound vibrations into neural signals that can be processed by the brain.
These hair cells have stereocilia that when bent by sound wave-induced vibrations, open ion channels leading to hair cell depolarization and the initiation of nerve impulses. Long-term pesticide exposure, according to toxicological research, can have endocrine-disrupting effects, including altering gene expression and potentially affecting hair cell function.
Given that Dr. Tanner observed the organ of Corti during his study, if pesticides disrupted auditory function, it is most likely that they caused damage to the hair cells, thereby preventing them from bending in response to sound and initiating the necessary electrical signals to the auditory nerve.
The correct option in the final answer, based on the information provided, is d. Pesticide exposure caused damage to hair cells, preventing them from bending in response to sound.