Section 0.1.4

Question 1

Describe pitch (tone)

Answer 1

Pitch or tone of a sound is determined by the frequency of vibrations. The greater the frequency, the higher the pitch.

Question 2

Describe intensity/loudness

Answer 2

Intensity or loudness depends on the amplitude of the sounds waves and the greater the amplitude, the louder the sound

Question 3

Describe timbre (quality)

Answer 3

The timbre or quality of a sound is the overtones that are superimposed on the pitch.

It allows one to locate the source of the sound as each source produces a different pattern of overtones.

Timbre also allows us to distinguish between voices and instruments even if they are creating the same tone

Question 4

Describe the function of the external ear, as well as name the parts

Answer 4

The primary function of the external ear is to channel sound waves to the middle ear and it is
comprised of three parts: the pinna, the ear canal, and the tympanic membrane

Question 5

What is the pinna?

Answer 5

The pinna is the external skin covered cartilage that collects the sound waves.

The pinna are essential for the location of sound. As we talked about two eyes and visual depth perception, two ears allow for
the precise pinpointing of sounds especially when combined with the ability to move the head to optimize sound localization

Question 6

What is the ear canal?

Answer 6

The ear canal conducts the sounds waves.

The entrance to ear canal is guarded by fine hairs and special cells secrete ear wax. The hairs and wax prevent airborne particles from entering the
ear canal, and have properties which aid in the defense against bacteria by making the environment more acidic

Question 7

What is the tympanic membrane?

Answer 7

The tympanic membrane stretches across the entrance to the middle ear and vibrates when hit by the incoming sound waves.

In order for the tympanic membrane to vibrate efficiently, the air pressure on both sides needs to be similar. The middle ear cavity is connected to the pharynx via the eustachian
tube, which allows the middle ear pressure to equalize with atmospheric pressure

Question 8

What are the bones of the middle ear?

Answer 8

The malleus, incus and stapes

Question 9

What is the function of the malleus, incus and stapes?

Answer 9

To transfer the movement of the
tympanic membrane and amplify the sound as it is transmitted to the fluid of the inner ear.

As the tympanic membrane vibrates, the malleus (which is attached to the inner surface of the tympanic membrane) transfers the vibration to the incus, which transfers it to stapes (which is attached to the
oval window)

The interface between the middle and inner ears is air to fluid, so without amplification the power
would be too weak for useful perception.
Conversely, when a loud sound is sensed, specialized muscles contract to restrict movement
of these bones and thus protect the inner ear.

Question 10

What is the function of the oval window?

Answer 10

To convert sound waves into mechanical energy, and transfer it to the inner ear

Question 11

What is the cochlea?

Answer 11

The cochlea is the part of the inner ear responsible for the perception of hearing.

Question 12

What is the organ of corti and the basilar membrane?

Answer 12

Within the cochlea is the organ of Corti, which is the actual sense organ, and is supported by the
basilar membrane.

The organ of Corti contains hair cells: one row of inner hair cells and three rows of outer hair cells. When fluid moves within the inner ear, the hair cells are mechanically deformed and they generate neuronal signal

Question 13

Describe the function of the inner hair cells in the cochlea

Answer 13

These hair cells transform the cochlear fluid vibrations into action potentials propagating auditory messages to the cortex. Changes of membrane potential in these cells match the frequency of the original sound stimulus

Question 14

Describe the function of the outer hair cells of the cochlea

Answer 14

These hair cells do not transmit sound signals to the brain.

Instead, these hair cells function to modify the electrical signalling of the inner hair cells. They enhance the response of the inner hair cells making them more sensitive to sound intensity and pitch.

Question 15

How does pitch discrimination occur?

Answer 15

Pitch discrimination is influenced by the basilar membrane’s changing shape, transitioning from narrow near the oval window to wide at the other end.

This variation in shape enables the distinction of different pitches; higher pitches (e.g., 20000 Hz) are perceived at the narrow end, while lower pitches (e.g., 200 Hz) are detected at the wider end. When the stapes moves the oval window at a specific pitch, the resulting wave travels to the corresponding region of the basilar membrane. In this region, hair cells experience maximum deformation, and the signal is transmitted to the central nervous system.

Question 16

Where do auditory signals travel?

Answer 16

The auditory nerve, composed of afferent neurons that collect auditory signals from the hair cells, carries these signals to the cortex. Along the way, the signals pass through the brainstem, which contributes to alertness and arousal, and the thalamus, responsible for sorting and forwarding the signals to higher processing centers.

Question 17

What is the purpose of the vestibular apparatus?

Answer 17

The inner ear houses the vestibular apparatus, which helps maintain balance and coordinate movements by detecting changes in head motion. This apparatus, like the cochlea, is filled with fluid and contains sensory hair cells that respond to fluid movement.

Notably, signals from the vestibular apparatus typically don’t reach conscious awareness. However, some individuals have an unusually sensitive vestibular apparatus, leading to motion sickness, characterized by dizziness and nausea.

Question 18

Where do signals from the vestibular apparatus go in the brain?

Answer 18

Signals from the vestibular apparatus are sent to the vestibular nuclei in the brainstem and to the cerebellum.

Question 19

What is the purpose of integrating vestibular information with signals from the skin, eyes, muscles, and joints?

Answer 19

Integrating vestibular information with other sensory signals helps:

• Maintain balance and posture
• Keep the eyes fixed when turning the head
• Perceive motion and orientation

Question 20

what happens if the tympanic membrane ruptures?

Answer 20

A perforated eardrum or tympanic membrane can be detrimental to hearing as it is the first point of
contact for sound waves entering the ear.

The tympanic membrane must be able to vibrate to transmit the sound waves to the bones of the middle ear. If the tympanic membrane is perforated, it cannot vibrate, and therefore no sound waves are transmitted to the inner ear and no sound is perceived

Question 21

What happens if the malleus is shattered?

Answer 21

The malleus is the first of the three bones of the middle ear. It is responsible for transmitting the sound waves received at the tympanic membrane to the other two bones of the middle ear.

If the malleus is shattered, it cannot transmit vibrations from the tympanic membrane properly and therefore sound is not perceived consciously

Question 22

They enhance the response of the inner hair cells making them more
sensitive to sound intensity and pitch

Answer 22

Outer hair cells

Question 23

The external skin covered cartilage that collects the sound waves.

Answer 23

Pinna

Question 24

The part of the inner ear responsible for the perception of hearing

Answer 24

Cochlea

Question 25

These transform the cochlear fluid vibrations into action potentials propagating auditory messages to the cortex

Answer 25

Inner hair cells

Question 26

The organ which provides information essential for equilibrium and coordination of movement by detecting changes in head movement

Answer 26

Vestibular apparatus

Question 27

Structure responsible for conducting sound waves

Answer 27

Ear canal

Question 28

The bone of the middle ear which is in direct contact with the tympanic membrane

Answer 28

Malleus

Question 29

Describe the different properties of sound waves.

Answer 29

Sound waves have several properties, including frequency (pitch), amplitude (loudness), and waveform (timbre). Frequency determines the pitch of sound, measured in Hertz (Hz). Amplitude indicates loudness, measured in decibels (dB). Waveform refers to the shape of the sound wave, which determines the quality or timbre of the sound.

Question 30

Describe how sound waves are transduced into a change in action potentials to the auditory cortex.

Answer 30

Sound waves are transduced into electrical signals in the ear. The process begins in the cochlea, where hair cells convert mechanical vibrations caused by sound waves into receptor potentials. These receptor potentials trigger the release of neurotransmitters, which stimulate afferent neurons to generate action potentials. These action potentials travel via the auditory nerve to the auditory cortex in the brain, where they are interpreted as sound perception.

Question 31

Describe the purpose of the vestibular apparatus and how it functions.

Answer 31

The vestibular apparatus is responsible for detecting changes in head movement and orientation, maintaining balance, and coordinating body movements. It contains sensory hair cells and is located in the inner ear. When the head moves, the movement of fluid within the semicircular canals of the vestibular apparatus stimulates hair cells, generating electrical signals. These signals are transmitted to the brainstem and cerebellum, which use the information to control balance and posture and ensure stable vision during head movements.