Unit Three: Equilibrium and Hearing Flashcards
What are the three anatomical regions of the ear?
- External ear. 2. Middle ear. 3. Internal ear.
What anatomical region of the ear contains the sensory organs for equilibrium (balance) and hearing?
The internal ear.
What does the external ear include? (2)
- The outer fleshy auricle. 2. External acoustic meatus.
What does the auricle protect? What does it provide?
The opening passageway and provides directional sensitivity to the ear by directing sound inward toward the tympanic membrane.
What is the tympanic membrane? What does it separate?
The eardrum. It is thin, semitransparent connective tissue separating the external ear from the middle ear.
What do ceruminous glands secrete?
Cerumen.
What does cerumen do?
Slows the growth of microorganisms and reduces the chance of infection.
What are ceruminous glands modifications of?
Sweat glands.
What does the middle ear consist of?
The tympanic cavity, which contains auditory ossicles.
What is the tympanic cavity?
An air-filled space that contains auditory ossicles.
What does the tympanic cavity communicate with? (2)
The nasopharaynx through the auditory canal. 2. Mastoid air cells.
Where does the auditory tube penetrate?
The petrous part of the temporal bone.
What is the auditory tube also called?
Eustachian tube.
What does the auditory tube do?
It helps equalize the pressure in the middle ear with external, atmospheric pressure.
What do the three bones comprising the auditory ossicles do?
They connect the tympanic membrane with the receptor complex of the internal ear.
What are the three auditory ossicles connected by? What do they do?
Synovial joints. They transfer sound vibrations from the tympanic membrane to a fluid-filled chamber within the internal ear.
What are the three auditory ossicles?
- Malleus. 2. Incus. 3. Stapes.
What is the oval window?
A hole in the bony wall of the middle ear cavity.
What does vibration of the tympanic membrane do?
It converts arriving sound waves into mechanical movements.
Describe the vibration of the auditory ossicles.
The malleus vibrates the incus. The incus vibrates the stapes.
What does the movement of the stapes do?
It causes vibrations in the fluid contents of the internal ear.
What is the auricle of the external ear made up of?
Elastic cartilage.
What two muscles reduce movements of the auditory ossicles in the ear?
- Tensor tympani muscle. 2. Stapedius muscle.
What muscle equalizes pressure?
Levator veli palatini.
What are the two divisions of the inner ear?
- Bony labyrinth. 2. Membranous labyrinth.
What does the bony labyrinth contain?
Perilymph.
What does the membranous labyrinth contain?
Endolymph.
Is perilymph and endolymph a byproduct of cerebrospinal fluid?
Yes.
What are the layers of the inner ear (from outside-in)? (4)
- Bony labyrinth. 2. Perilymph. 3. Membranous labyrinth. 4. Endolymph.
What can the membranous labyrinth be divided into? (2)
- Cochlear duct (hearing). 2. Vestibular complex (equilibrium).
What can the vestibular complex include? (2)
- Semicircular ducts (rotation). 2. Utricle and saccule (gravity and linear acceleration).
Where do high frequency sounds stimulate the spiral organ?
More proximal to the oval window.
Where do low frequency sounds stimulate the spiral organ?
Closer to the apex of the cochlea.
What 3 channels are the cochlea divided into?
- Scala vestibuli. 2. Scala tympani. 3. Cochlear duct.
What does the spiral organ detect?
Endolymph movement.
What is the tectorial membrane?
The overlying gelatinous mass the stereocilia project into.
Where does the spiral organ sit?
On the basement membrane.
What do spiral organs contain?
Thick sensory epithelium with hair cells.
Describe the path of sound waves through the ear (1-4).
- Tympanic membrane. 2. Auditory ossicles. 3. Oval window. 4. Scala vestibuli.
Describe the path of sound waves through the ear from the scala vestibuli (3).
- Cochlear duct. 2. Scala tympani. 3. Round window.
In what Brodmann’s area is the primary auditory cortex?
41, 42.
Describe the first 3 steps of the CNS pathway of audition.
- Basilar membane. 2. Cochlear part of CN VIII. 3. Brainstem nuclei (Cochlear nucleus).
Describe the second 3 steps of the CNS pathway of audition.
- Medial geniculate nucleus (thalamus). 2. Primary auditory cortex. 3. Auditory association cortices.
What does the utricle allow for?
An understanding of horizontal movement.
What does the saccule allow for?
An understanding of vertical movement.
What is the macula of the utricle and saccule?
The portion of the above regions that contain hair cells.
What are stereocilia and kinocilia embedded in?
A gelatinous layer covered in otoliths.
What are the three semicircular canals/ducts?
- Anterior. 2. Posterior. 3. Lateral.
What is the ampulla?
The expanded region of each semicircular canal.
What is the cupula?
The overlying gelatinous dome that stereocilia and kinocilia are embedded into.
What semicircular duct is sensitive to “yes?”
Anterior.
What semicircular duct is sensitive to “no?”
Lateral.
What semicircular duct is sensitive to “tilting head?”
Posterior.
What happens when the head rotates?
The endolymph moves and pushes against the cupula and bends the stereocilia.
Describe the CNS pathway for vestibulation (2).
- Vestibular part of CN VIII. 2. Vestibular nuclei (medulla).
What occurs in the CNS pathway for vestibulation once the sensory info reaches the medulla? (2)
- Integration of sensory info. 2. Info gets relayed to cerebellum, cerebral cortex, spinal cord, CN III, IV, VI, XI.
What nerves receive information from the vestibulation pathway? (4)
- III. 2. IV. 3. VI. 4. XI.
Describe the path of where vestibular nuclei relay information (4).
- Cerebellum. 2. Motor nuclei of the extra-ocular muscle of the eye. 3. Cerebral cortex to provide conscious sens of position and movement. 4. To other motor nuclei in the brainstem and spinal cord.
