Question

Vibrations of the _____, located within the _____, bend stereocilia in the hair cells of the mammalian ear and activate sensory neurons. a. tympanic membrane, cochlear duct b. round window, middle ear c. basilar membrane, organ of Corti d. ossicle, outer ear e. ampulla, semicircular canals

Short answer

The correct answer is (c) basilar membrane, organ of Corti.

Step-by-step solution

Identify the Vibrational Element

The element that vibrates in response to sound waves within the ear is the basilar membrane, which acts as a type of mechanical analyzer and speaker, separating out the frequencies of incoming sound waves.

Identify the Location

These vibrations of the basilar membrane occur within the organ of Corti, the sensory organ of hearing which is located on the basilar membrane in the cochlea of the inner ear.

Confirmation

Referencing this information, the correct answers to fill in the blanks of the given question are 'basilar membrane' and 'organ of Corti' respectively, making option (c) the correct choice.

Key concepts

Organ of Corti

The organ of Corti is the epicenter of our hearing capabilities. Situated on the basilar membrane inside the cochlea, it harbors an array of hair cells, which are the true heroes in converting sound vibrations into electrical signals. This assembly looks akin to a tiny piano, with each 'key' tuned to a specific frequency. Sound waves travel through the ear canal, vibrate the eardrum, and get transferred into the cochlea. It is here that the organ of Corti comes into play.

When the basilar membrane vibrates, so does the organ of Corti, leading to the bending of hair cell stereocilia – little hair-like projections. This bending is crucial; it causes a chemical change that generates electrical signals, which neurons pick up. This orchestration exemplifies how mechanical energy (sound waves) is transformed into the language of our nervous system – electrical impulses.

Cochlea

Imagine a snail's shell, with its coiled structure; that's pretty much what the cochlea in your inner ear looks like. But don't let its small size fool you; it's a powerhouse of auditory transduction. The cochlea is filled with fluid and lined with the basilar membrane. Sound vibrations cause this fluid to ripple, much like stones thrown in a pond. These ripples move the basilar membrane, thus stimulating the organ of Corti resting on top of it.

Due to the coiled shape of the cochlea, it can accommodate a wide range of sound frequencies along its length, with high frequencies detected at the base and low frequencies at the apex. It's a remarkable example of nature's design efficiency – packing a sophisticated frequency analyzer into such a compact space. Understanding this structure helps us appreciate how delicate and finely tuned our hearing is.

Sensory Neurons

Sensory neurons are the messengers of the body, announcing to the brain that something is happening in the environment. In the context of hearing, these neurons are like the audience receiving a performance by the organ of Corti. Once the hair cells inside the organ of Corti send out their electrical impulses, these neurons pick up the signal.

They carry this information to the brain along the auditory nerve, allowing us to perceive and interpret sounds. The speed and precision with which these neurons operate allow us to instantly recognize sounds and even determine their direction. When studying sensory neurons, it's important to grasp that they are the final translators of the sensory input, enabling us to experience the rich soundscape of our world.