Hearing video

Question 1

Describe the ear fucntions

Answer 1

• Detects sound and movements of the head
• Signals transmitted via vestibulocochlear nerve (CN VIII)
• Partitioned into external, middle, and inner ear

Question 2

What are three parts of the ear?

Answer 2

1. External (outer) ear
2. Middle ear
   (tympanic cavity)
3. Internal (inner) ear

Question 3

What is the auricle composed of?

Answer 3

• Helix (rim)
• Lobule (earlobe)

Question 4

What is external acoustic meatus?

Answer 4

• Short, curved tube lined with skin bearing hairs, sebaceous glands, and ceruminous glands

Question 5

What is typanic membran ( eardrum)

Answer 5

• Boundary between external and middle ears
• Connective tissue membrane that vibrates in response to sound
• Transfers sound energy to the bones of the middle ear

Question 6

Structure of middle ear

Answer 6

A small, air-filled, mucosa-lined cavity in the temporal bone
- Flanked laterally by the eardrum
- Flanked medialy by biny wall containing the oval and round windows.

Question 7

What are ear ossicles?

Answer 7

Three small bones in tympanic cavity: the malleus, incus, and stapes
- Suspended by ligaments and joined by synovial joints
- Transmit vibratory motion of the eardrum to the oval window
- Tensor tympani and stapedius muscles contract reflexively in response to loud sounds to prevent damage to the hearing receptors

Question 8

What are the names of the auditory ossicles, where are they located, and what is their function?

Answer 8

The malleus, incus, and stapes are located in the tympanic cavity of the middle ear. They amplify and transmit sound waves into the inner ear via the oval window.

Question 9

What is a vestibule?

Answer 9

• Central egg-shaped cavity of the bony labyrinth
• Contains two membranous sacs
  1. Saccule is continuous with the cochlear duct
  2. Utricle is continuous with the semicircular canals
• These sacs
• House equilibrium receptor
  regions (maculae)
• Respond to gravity and changes in the position of the head

Question 10

What are Semicircular Canals?

Answer 10

• Three canals (anterior, lateral, and posterior) that each define two-thirds of a circle
• Membranous semicircular ducts line each canal and communicate with the utricle
• Ampulla of each canal houses equilibrium receptor region called the crista ampullaris
  Receptors respond to angular (rotational) movements of the head

Question 11

What is the cochlea

Answer 11

A spiral, conical, bony chamber
- Extends from the vestibule
- Coils around a bony pillar (modiolus)
- Contains the cochlear duct, which houses the spiral organ (of Corti) and ends at the cochlear apex

Question 12

Describe inner ear

Answer 12

• Bony labyrinth
• Tortuous channels in the temporal bone
• Three parts: vestibule, semicircular canals, and cochlea
• Filled with perilymph
• Series of membranous sacs within the bony labyrinth
• Filled with a potassium-rich endolymph

Question 13

What structures compose the bony labyrinth?

Answer 13

The cochlea, vestibule, and semicircular canals

Question 14

Structures for hearing

Answer 14

Cochlea
- Snail-shaped spiral chamber within bone of inner ear
- Has spongy bone axis, modiolus
- Houses the spiral organ, responsible for hearing
- Cochlear duct
* membranous labyrinth that extends through cochlea
* roof formed by vestibular membranes
* floor formed by basilar membranes

Question 15

What are the three chambers of the cochlea

Answer 15

The cavity of the cochlea is divided into three chambers
- Scala vestibuli-abuts the oval window, contains perilymph
- Scala media (cochlear duct) - contains endolymph
- Scala tympani-terminates at the round window; contains perilymph
* The scalae tympani and vestibuli are continuous with each other at the helicotrema (apex)

Question 16

What is sound?

Answer 16

• A pressure disturbance (alternating areas of high and low pressure) produced by a vibrating object

Question 17

What is a sound wave?

Answer 17

• Moves outward in all directions
• Is illustrated as an S-shaped curve or sine wave

Question 18

Describe Transmission of Sound to the Internal Ear

Answer 18

• Sound waves vibrate the tympanic membrane
• Ossicles vibrate and amplify the pressure at the oval window
• Pressure waves move through perilymph of the scala vestibuli
• • Waves with frequencies below the threshold of hearing travel through the helicotrema and scali tympani to the round window
• Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane at a specific location, according to the frequency of the sound

Question 19

Auditory Pathways to the Brain

Answer 19

• Impulses from the cochlea pass via the spiral ganglion to the cochlear nuclei of the medulla
• From there, impulses are sent to the
• Superior olivary nucleus
• Inferior colliculus (auditory reflex center)
• From there, impulses pass to the auditory cortex via the thalamus
• Auditory pathways decussate so that both cortices receive input from both ears

Question 20

Trace the auditory pathway through the brain.

Answer 20

Cochlear nerve axons extend to the cochlear nucleus in the medulla. Some axons project directly to the inferior colliculus. Others project to the superior olivary nucleus first, before synapsing with neurons that extend to the inferior colliculus. Axons from neurons in the inferior colliculus project to the medial geniculate nucleus of the thalamus. These neurons project to the primary auditory cortex.