P/S Ch.2 Hearing and Vestibular Sense

The ear is divided into three parts: ______, _________, and _______.

1. Outer ear: also called the pinna or auricle

--- divided by the tymphanic membrane ---

2. Middle ear

3. Inner ear

What are the structures of the outer ear (also known as the pinna or auricle?)

1. External auditory canal

2. Tympanic membrane (eardrum)

What does the external auditory canal do?

Direct soundwaves from the pinna to the eardrum.

What does the tympanic membrane (eardrum) do?

It vibrates in phase with the incoming sound waves.

What are the three parts of the ossicles and what do they do?

The ossicles in general help transmit and amplify the vibrations from the eardrum to the inner ear.

1.Stapes - Stirrup

2.Incus - Anvil

3. Malleus - affixed to the eardrum, which acts on the incus, which acts on the stapes

How is the middle ear connected to the nasal cavity? What does this structure help do?

Through the Eustachian tube, which helps equalize pressure between the middle ear and the environment.

In the inner ear, the ___ labyrinth is filled with ________ and the _______ labyrinth is filled with ________.

1. Bony labyrinth; perilymph (purple) - cushions the inner ear structures

2. Membranous labyrinth; endolymph (blue) - which is potassium rich

The bony labyrinth surrounds the membranous labyrinth.

The ______ is a spiral-shaped organ that has the receptors for hearing. And is divided into three parts called the ______.

Cochlea; scalae.

What is the organ of corti?

It is the actual hearing apparatus. It contains hair cells that transduce the physical stimulus into an electrical signal, which is carried to the CNS.

By what nerve is the electrical signal from the organ of Corti sent to the CNS?

Through the auditory (vestibulocochlear) nerve.

What is the vestibule?

The portion of the bony labyrinth that has the utricle and saccule. It is sensitive to linear acceleration.

How does the vestibule detect linear acceleration?

The vestibule is covered in modified hair cells covered with otoliths. As the body accelerates, the otoliths resist the motion of the body, which sends a signal to the brain.

What physical motion is the semicircular canals sensitive to?

Rotational acceleration. The canals are arranged perpendicularly to each other, and each ends in a swelling called an ampulla, where the hair cells are located. Endolymph in the semicircular canal resist rotational motion, which bends the underlying hair cells, which sends a signal to the brain.

Sound information passes through the __________ to the __________, where it ascends to the _________.

Vestibulocochlear nerve; brainstem; medial geniculate nucleus

From the medial geniculate nucleus, where does the nerve fibers project?

To the auditory cortex in the temporal lobe for sound processing.

What brain structure is involved with reflexive stimulus to sound?

Just like the superior colliculus = eyes, the inferior colliculus is involved in the startle reflex.

As vibrations reach the basilar membrane underlying the organ of Corti, the _______ cells begin to say back and forth in the endolymph.

Stereocilia (hair cells)

What is place theory?

The location of a hair cell on the basilar membrane determines the perception of pitch when that hair cell is vibrated.