Hearing

What are the two main characteristics according to which the auditory system analyzes sounds?

Frequency and Amplitude.

How is sound intensity measured in decibels?

dB SPL = 20 log10(Po/Pr).

What is defined as a complex sound with a pitch of 500 hertz?

A mixture of A, B, C, D.

What is the function of the outer ear?

Funnel sound into the ear canal, provide amplification, protection, and sound localization.

What are the structures of the outer ear?

Pinna or auricle, lobe, tragus, helix, antihelix, antitragus, external auditory meatus.

What separates the outer ear from the middle ear?

Tympanic membrane.

What are the three tiny bones of the ossicular chain?

Malleus, incus, stapes.

What is the purpose of the acoustic reflex?

To make sound transmission more difficult and protect hearing from loud sounds.

Which cranial nerves innervate the muscles of the middle ear?

Facial nerve (CN 7) and trigeminal nerve (CN 5).

What is the pharyngotympanic tube's role in the middle ear?

It maintains equal pressure between the middle ear and the atmosphere.

Why are children more prone to ear infections?

The middle ear is flatter, wider, and shorter compared to adults.

What is the period in acoustics?

The period is the amount of time it takes for one complete wave cycle to occur.

What does SPL stand for?

Sound Pressure Level.

What does Sd SPL refer to?

the level of sound intensity or pressure.

What is the External Auditory Meatus (EAM)?

The canal that leads to the tympanic membrane (TM).

What are the functions of the middle ear?

To impedance match (overcome air-water transmission problem) and equalize air pressure.

What are the two muscles involved in protecting hearing from loud sounds?

Tensor tympani and stapedius.

What happens when the tensor tympani and stapedius muscles contract?

They make sound transmission more difficult and protect hearing during very loud sounds.

What is the role of the pharyngotympanic tube in the middle ear?

Sound is perceived as vibrations, and the inner ear is filled with fluid, requiring amplification for effective hearing. 20:1 amplification

What is the Oval window?

The entry point to the inner ear, where the stapes bone connects to the cochlea.

What is the function of the Eustachian tube?

It connects the middle ear to the nasopharynx, allowing air to travel back and forth and helping to equalize pressure. Drains waste and fluid

What fills the tympanic cavity?

mainly air

What happens with a problem in the Eustachian tube?

It can result in fluid buildup in the middle ear, often leading to ear infections, especially in young children.

What is the function of the inner ear?

The sense of hearing occurs, as well as sensory perception of motion and position.

What is the Cochlea?

A snail-shaped structure (2 ¾ turns) that is 35 mm in length (if unrolled) and filled with fluid, integral for hearing.

What are the three chambers inside the cochlea and their fluid types?

Scala vestibuli (filled with perilymph), Cochlear duct (scala media, filled with endolymph), and Scala tympani (filled with perilymph).

What is the structure and function of the Organ of Corti?

• key sensory structure for hearing, located on the basilar membrane. -

• inner hair cells, which transmit 90% of auditory information in one row

• outer hair cells, which transmit 10% of auditory information in three rows.

How does the auditory system code for frequency and intensity?

involves,,,

• Place Theory: where hair cells at distinct sites along the basilar membrane respond to different frequencies

• Temporal Theory, relies on the relative timing of impulses in individual neurons to convey frequency information. Intensity is represented by action potentials.

What is amplitude in relation to sound?

the displacement of the basilar membrane, which is converted into neural firing rates.

What is transduction in relation to hearing in the cochlea?

1. Stapes moves against the oval window, causing cochlear fluid to vibrate.

2. The basilar membrane vibrates in response; thin, stiff base responds to higher frequencies, while the wide, flaccid apex responds to lower frequencies.

3. This movement displaces organs of Corti toward the tectorial membrane, shearing the stereocilia of hair cells against it and releasing neurotransmitters.

4. Auditory nerve endings synapse with hair cells, generating nerve impulses conducted to the brain.

Transduction

Changing to mechanical vibrations to electricity, uses electrical signals for the what the brain hears

What is the impact of 30 dB hearing loss from air to water?

Moderate hearing loss is characterized by a loss within this range, impacting sound perception and clarity due to the transition between air and water conduction.