Lecture 10 - The Inner Ear and Balance Flashcards
What are the structures of the outer ear?
Auricle (pinna) and external auditory canal
Function of the auricle (pinna)?
Gathers sound waves, aids in localization, amplifies sound
External auditory canal
Allows air to warm before reaching tympanic membrane (TM).
Isolates TM from physical damage. Cerumen glands moisten/soften skin.
Tympanic cavity
Small chamber, lying in the depth of the temporal bone, between the tympanic membrane and the internal ear.
In front, through the ___________, the tympanic cavity communicates with the _________.
- Eustachian tube
- nasopharynx
Behind, through the entrance into the mastoid antrum, communicates with the latter and the cells of the ________.
mastoid process
What are the parts of the inner ear?
Boney portion (bony labyrinth)
Membranous portion (membranous labyrinth)
Membranous labyrinth is filled with fluid, known as _________ and is separated from the bony labyrinth by a fluid called ________.
- endolymph
- perilymph
What does the membranous labyrinth consist of?
- Three semicircular canals
- Two otolith organs
- Cochlea
What are the 3 semicircular canals?
- Horizontal (lateral)
- Anterior (superior)
- Posterior (inferior)
What are the 2 otolith organs?
Saccule and utricle
Function of the 3 semicircular canals?
Detect angular/rotary acceleration and deceleration of the head.
Function of the 2 otolith organs (utricle and saccule)?
Detect linear acceleration and deceleration, and static tilt of the head.
Function of vestibular nerve fibers?
Synapse with hair cells.
Endolymph flows within the __________.
membranous labyrinth
Perilymph flows between the _____________.
bony labyrinth and the membranous labyrinth
The ionic composition of perilymph is similar to that of blood plasma and cerebrospinal fluid. The major cation is _______.
Na+
Endolymph has a unique ionic composition, featuring a high concentration of _______ ions, which is unique among extracellular fluids.
K+
The presence of K+ ions in the extracellular fluid creates a greater electrical potential, making the hair cells ___________.
much easier to depolarize to generate action potentials
Crista ampullaris
Sense organ in the semicircular canal.
in each ampulla of the semicircular canals, there is a ________ whose cilia project into gelatinous mass called a cupula.
crest of hair cells
Cupula
Gelatinous mass
Otoliths
Calcium carbonate crystals
The cilia from all hair cells project into a gelatinous mass. Displacement of the mass in a given direction causes all the hair cells to ________.
bend in that direction
Hair cells are the sensory receptors of both ___________.
auditory system and vestibular system.
Utricle and saccule each contain a _______, which transduces _________.
- macule
- static head tilt, linear acceleration and deceleration
When rotation moves in one direction, bending of the cilia causes the hair cells to _________ and impulses reach the brain at a _________.
- depolarize
- faster rate
In the utricle and saccule, the hair cell receptor is called the ______.
macula
Both the utricle and saccule respond to acceleration. The utricle responds to ____________ acceleration and saccule responds to _____________ acceleration.
- horizontal
- vertical
Acceleration in a given direction results in bending of the hair cell cilia in the __________.
opposite direction
Vestibular reflexes coordinate ___________ movements.
eye and head
Vestibular Ocular Reflex (VOR)
When rotation starts, eyes move slowly in the direction opposite the rotation, maintaining visual fixation.
The eyes are controlled by what three pairs of muscles?
- medial/lateral rectus
- superior/inferior rectus
- inferior/superior oblique
