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Where are the sensory cells located for equilibrium and hearing?
Within the inner ear, where sensory info is integrated and organized before it is sent to the CNS, (as opposed to being within epithelia in the external environment like in olfaction and gustation)
What are the receptor cells of the inner ear called?
Why are the receptor cells of the inner ear called "hair cells"?
Because their free surfaces are covered with specialized processes similar to cilia or microvilli
What type of sensory receptor are hair cells?
Mechanoreceptors, sensitive to contact or movement; the forces that push against them distort the plasma membrane and alters the rate at which neurotransmitters are released
What is the name of the hair cells that are involved in balance?
Kinocilium (a single large cilium)
What is the name of the support cells associated with hair cells?
Stereocilia (which resemble long microvilli)
The ear is divided into 3 anatomical regions, what are they?
- 1) External Ear
- 2) Middle Ear
- 3) Internal Ear
This is the visible portion of the ear that collects and directs sound waves toward the middle ear.
This portion of the ear goes by 2 names, and is an air-filled cavity separated from the external acoustic meatus by means of the tympanic membrane.
Middle Ear, or Tympanic Cavity
This portion of the ear contains the sensory organs for hearing and equilibrium.
This structure consists of elastic cartilage and is used to collect sound waves and funnel them into the external acoustic meatus.
This is the passageway within the temporal bone through which sound waves travel from the external ear to the tympanic membrane.
External Acoustic Meatus
These glands secrete ear wax and are located in the lining of the external acoustic meatus.
What is the wax in the ear called?
What are the 2 functions of cerumen (ear wax)?
- 1) Helps keep foreign objects from reaching delicate, internal structures
- 2) Slows the growth of microorganisms in the external acoustic meatus, reducing the chances of an ear infection
This structure, known as the ear drum, lies at the end of the eternal auditory meatus and separates the external ear from the internal ear.
This structure permits pressure equalization on either side of the tympanic membrane.
The inner ear contains 3 auditory ossicles (bones), Name them in order from the outside in.
- 1) Malleus
- 2) Incus
- 3) Stapes
This is a collection of fluid-filled tubes and chambers in the inner ear.
The membranous labyrinth contains a fluid required for receptor cell function called what?
This is a shell of dense bone that surrounds and protects the membranous labyrinth.
The bony labyrinth is composed of 3 parts, what are they?
- 1) Semicircular Canals
- 2) Vestibule
- 3) Cochlea
This part of the inner ear provides equilibrium sensations by detecting rotation, gravity, and liner acceleration.
This specific portion of the vestibular complex consists of 3 semicircular canals which detect rotational movements of the head in 3 different planes.
This specific portion of the vestibular complex consists of 2 chambers with receptors that are sensitive to head position relative to gravity. They also respond to acceleration.
Utricle and Saccule
The movement of the stapes at the oval window generates pressure waves that stimulate hair cells at specific locations along the length of this structure, and is used in hearing.
Cochlear Duct (hearing)
The hair cells of the utricle and saccule are clustered in oval structures called what?
Each semicircular duct contains a ______, an expanded region that contains the receptors; is filled with endolymph.
The region in the wall of the ampulla that contains the receptors; is bound to the cupula.
A flexible, elastic, gelatinous structure that extends the full width of the ampulla; is bound to the crista ampullaris.
Hair cells in the semicircular ducts respond to _____; Hair cells in the utricle and saccule respond to _____ and _____
Rotation; Gravity; Linear Acceleration
A horizontal rotation, as in shaking your head "no" stimulates the _____ semicircular duct; Nodding "yes" excites the _____ duct; Tilting your head from side to side activates receptors in the _____ duct.
Lateral; Anterior; Posterior
The hair cell processes of the maculae are embedded in this gelatinous membrane whose surface contains densely packed calcium carbonate crystals called otoliths.
Calcium carbonate crystals called "ear stones" that sit atop the otolithic membrane of the macula; When the head tilts, they shift, distorting the hair cell processes and stimulating receptors.
What is the structure where mechanical vibrations are changed to electrical impulses?
The Organ of Corti
The organ of corti has 5 main structures, what are they?
- 1) Tectoral Membrane
- 2) Basilar Membrane
- 3) Inner Hair Cell
- 4) Outer Hair Cell
- 5) Nerve Fibers
The hair cells of the organ of corti are in contact with the overlying _____; Sound waves create pressure against it, stimulating the underlying hair cells.
This structure, on which the organ of corti lies, separates the cochlear duct from the scala tympani.
List the 6 events involved in hearing.
- 1) Sound waves arrive at the tympanic membrane
- 2) Movement of tympanic membrane causes displacement of auditory ossicles
- 3) Movement of stapes at the oval window creates pressure waves in the perilymph of the scala vestibuli
- 4) The pressure waves distort the basilar membrane
- 5) Vibration of the basilar membrane causes vibration of hair cells against the tectoral membrane
- 6) Info about the region and intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII