Questions: Which of the following statements is true? Sound coming into the ear first encounters the cochlea. The otolith organ carries signals from the inner ear to the brain. Sound is mechanical energy that travels in the form of subatomic particles. The tectorial membrane is a structure in the cochlea that hair cells interact with to produce action potentials.

The answer is the fourth one: The tectorial membrane is a structure in the cochlea that hair cells interact with to produce action potentials.

Explanation for each option:

1. Sound coming into the ear first encounters the cochlea.
   This statement is incorrect. Sound first encounters the outer ear, specifically the pinna and the ear canal, before reaching the cochlea. The cochlea is part of the inner ear, and sound must pass through the outer and middle ear before reaching it.

2. The otolith organ carries signals from the inner ear to the brain.
   This statement is incorrect. The otolith organs (utricle and saccule) are part of the vestibular system in the inner ear and are responsible for detecting linear accelerations and head position relative to gravity. They do not carry signals themselves; rather, they send signals to the brain via the vestibular nerve.

3. Sound is mechanical energy that travels in the form of subatomic particles.
   This statement is incorrect. Sound is a form of mechanical energy, but it travels as waves through a medium (such as air, water, or solids), not as subatomic particles.

4. The tectorial membrane is a structure in the cochlea that hair cells interact with to produce action potentials.
   This statement is correct. The tectorial membrane is located in the cochlea, and it plays a crucial role in the auditory process. Hair cells in the cochlea interact with the tectorial membrane, and this interaction leads to the generation of action potentials that are sent to the brain for sound processing.

In summary, the correct statement is that the tectorial membrane is a structure in the cochlea that hair cells interact with to produce action potentials.