Test: Sound (Audition) - 1 - MCAT MCQ

The oval window forms the border between the middle ear and the inner ear. It is a membrane-covered opening that separates the middle ear, which contains the ossicles (including the incus), from the fluid-filled cochlea of the inner ear. When sound waves vibrate the eardrum, the vibrations are transmitted through the ossicles to the oval window, initiating the process of auditory transduction in the inner ear.

The tensor tympani is a muscle in the middle ear that is responsible for dampening the vibrations of the tympanic membrane (eardrum) in response to loud sounds. When exposed to intense sound waves, the tensor tympani contracts, pulling the tympanic membrane tighter. This reduces its ability to vibrate freely and limits the amount of sound energy that is transmitted to the inner ear. By tightening the tympanic membrane, the tensor tympani helps protect the delicate structures of the inner ear from damage caused by excessively loud sounds.

The ossicles, which consist of the malleus (hammer), incus (anvil), and stapes (stirrup), are small bones located in the middle ear. They play a crucial role in amplifying sound waves as they travel from the outer ear to the inner ear. When the tympanic membrane (eardrum) vibrates in response to sound waves, the vibrations are transmitted to the ossicles. The malleus is connected to the tympanic membrane and transfers the vibrations to the incus, which then transfers them to the stapes. The stapes is attached to the oval window, a membrane-covered opening that leads to the inner ear. The transfer of vibrations from the larger surface area of the tympanic membrane to the smaller surface area of the oval window results in mechanical amplification of the sound waves, allowing for more efficient transmission of sound energy into the fluid-filled cochlea of the inner ear.

• Loudness is dependent on both sound pressure and frequency.
• Points along the equal loudness curve are all perceived at the same volume. Therefore, all points on the threshold of feeling would be at the threshold of pain.
• Point A is below the threshold of hearing and would be inaudible.
• Points B and D both fall along the same equal loudness curve.
• Point C is located on an equal loudness curve above the equal loudness curve that contains points B and D.

The given scenario demonstrates the phenomenon of cross-modal interaction, where auditory information (the click sound) influenced the visual perception of the participants. In the first condition, without the click sound, the majority of participants perceived the objects as passing each other. However, in the second condition, when the click sound coincided with the visual perception of the objects being close together, a significant number of participants perceived the objects as bouncing off each other.

This suggests that the auditory input (the click sound) influenced or modulated the participants' visual perception, leading to a different interpretation of the visual stimulus. It highlights the integration and interaction of sensory information from different modalities, indicating that the auditory system can impact visual perception.

Loudness is a perceptual attribute of sound that refers to the subjective perception of sound intensity or volume. It is not a direction in auditory space but rather a quality of sound perception. On the other hand, azimuth, elevation, and distance are all directions in auditory space.

• Azimuth refers to the horizontal direction or angle of a sound source relative to the listener's head. It determines whether a sound is perceived as coming from the left or right side.
• Elevation refers to the vertical direction or angle of a sound source relative to the listener's head. It determines whether a sound is perceived as coming from above or below.
• Distance refers to the perceived spatial distance or proximity of a sound source from the listener. It relates to the perception of how near or far a sound source is.
• While loudness is an important attribute of sound perception, it does not indicate a specific direction in auditory space.

 The potassium channel in the hair bundle of the auditory system is a type of ion channel that is gated by mechanical stimuli. When sound vibrations cause the hair bundle to bend, it exerts tension on the mechanosensitive channels, including the potassium channels. This mechanical force opens or closes the channel, allowing the flow of potassium ions.

Therefore, the potassium channel in the hair bundle is classified as a mechanical gate because it responds to physical forces or mechanical stimuli, such as the bending of the hair bundle. This mechanical gating mechanism plays a crucial role in the transduction of sound vibrations into electrical signals in the auditory system.

The stapes is the third bone of the middle ear and is connected to the oval window, which is a membrane-covered opening between the middle ear and the inner ear. When the stapes pushes against the membrane covering the oval window, it generates pressure waves in the fluid-filled cochlea of the inner ear.

These pressure waves cause the basilar membrane, a component of the cochlea, to vibrate. The organ of Corti, which sits on the basilar membrane, contains hair cells responsible for transducing sound vibrations into electrical signals. The pressure changes transmitted by the stapes and the resulting vibrations of the basilar membrane cause the organ of Corti to vibrate vertically.

The vertical vibrations of the organ of Corti result in the bending of hair cells and the activation of auditory receptor cells, initiating the process of auditory transduction and leading to the perception of sound.

The cochlea is the primary structure in the auditory system responsible for encoding sound frequency. It contains the sensory hair cells that detect different frequencies of sound vibrations and convert them into electrical signals that can be transmitted to the brain.

The eustachian tube connects the middle ear to the back of the throat. Its primary function is to equalize the pressure between the middle ear and the outside environment. This is important for maintaining optimal sound transmission and preventing discomfort or damage to the structures of the middle ear.