CSD 357 - Midterm

What type of movement do semicircular canals (SCCs) detect?

Detects rotational (angular) acceleration via endolymph movement in response to head rotation.

What is the primary function of the utricle and saccule?

They detect linear acceleration and gravitational pull, utilizing the otolithic membrane and otoconia.

Which vestibular structure is key for horizontal acceleration, and provide an example?

The utricle; it detects horizontal acceleration, like forward and backward movement in a car.

What role do the maculae and otolithic membrane play in the vestibular system?

They provide inertia, detecting tilt and straight-line movement by sensing direction and intensity.

At what stage does hearing begin, and how is it conducted?

Hearing begins at 25 weeks gestation through bone conduction.

How does the tympanic membrane develop, and what are its layers?

It forms from ectoderm, mesoderm, and endoderm, with layers being outer (skin), middle (fibrous), and inner (mucous membrane).

What changes occur in the hearing threshold from birth to 10 years?

Significant improvements from birth to 4 years, slower gains from 4 to 10, and no improvements beyond that.

Describe tonotopic organization in the cochlea.

The cochlea encodes different frequencies in an organized manner, with high frequencies near the base and low frequencies near the apex (helicoterma)

What is phase locking and at what frequencies is it most effective?

Phase locking is when nerve fibers fire in sync with a sound wave's phase, effective for frequencies below 1,000 to 4,000 Hz.

What are the two types of auditory afferent neurons and their functions?

Type I neurons connect to Inner Hair Cells, encoding sound detail, while Type II neurons connect to Outer Hair Cells, modulating sound sensitivity.

What are the main parts of the auricle (pinna) and their functions?

Helix (outer rim), antihelix (inner ridge), tragus, antitragus, concha; these structures collect and funnel sound into the ear canal.

What is the role of the external auditory meatus (ear canal)?

It directs sound waves to the tympanic membrane and helps protect the ear by distancing it from outside world (temp&humidity regulation)

How does the tympanic membrane contribute to hearing?

It converts sound waves into mechanical vibrations, essential for transmitting sound to the middle ear, which then will go the inner ear via ossicles

Name the most important amplification mechanism that overcome air-to-fluid impedance mismatch.

Areal ratio advantage

NOT: curved membrane and ossicle lever action but they also effect it

Describe the middle ear reflex and its function.

The reflex stiffens the ossicles to reduce transmission of low-frequency sounds in response to loud noise, protecting the inner ear.

How does the Eustachian tube assist the ear?

It equalizes air pressure on both sides of the tympanic membrane

What is the most common cause of genetic hearing loss?

Connexin 26, which is non-syndromic