Lecture 4: Hearing and the Vestibular Senses Flashcards
The scala vestibuli and scala tympani are continous, fluid-filled compartments which contain?
Perilymph
Perilymph is most similar to what kind of fluid and what is its ion content like?
- Most similar to ECF
- High in [Na+] and low [K+]
Where is Endolymph found, what is it most similar to, and what is its ions concentrations like?
- Found in the Scala Media
- Most similar to ICF
- High in [K+] and low in [Na+]
What creates the chamber (scala media) that is isolated from the periymph?
The Basilar and Reissner’s membrane
The composition of the _____ will have a significant effect on the transduction of sound waves into actions potentials?
- Endolymph
- Large electrical gradient (scala media has high positive charge)
What components of the ear transmit and amplify the sound waves from the tympanic membrane to the oval window of the cochlea?
The ossicles
High frequency (short wavelength) sounds cause the maximum vibration of the basilar membrane where?
Closest to the oval window
Low frequency (long wavelength) sounds cause the maximum vibration of the basilar membrane where?
Farthest away from the oval window (towards to helicotrema)
Hair cells of the ear are what kind of receptors and convert what kind of energy?
- Mechanoreceptors
- Convert mechanical signal to an electric signal
What is each hair cell composed of that increase in length; what are they connected to and the function?
- Composed of distinct arrangement of shorter sterocilia that increase in length
- Each stereocilia connected to another at the top by an extracellular filamentous protein, known as the tip link
- This links the stereocilia together, allowing for deflection as a bundle
During transduction, if the stereocilia are bent towards the kinocilium (tallest stereocilia) what occurs?
- K+ ions enter the hair cell
- Hair cell depolarizes and opens voltage-gated Ca2+ channels
- Incoming Ca2+ leads to release of glutamate from synaptic vesicles
During transduction, if the stereocilia are bent away from the kinocilium (tallest stereocilia) what occurs to the hair cell?
Hair cell hyperpolarizes
Deflection of the stereocilia causing depolarization also causes the release of what NT and generates what?
- Release of glutamate
- Generation of AP’s in 8th nerve fibers
Which hair cells are primary source of auditory information and which act as an amplifier?
- One row of inner hair cells = primary source of auditory info
- Three rows of outer hair cells = acts as an amplifier
Hair cells have both afferent and efferent innervation, what type of afferents are the inner hair cells vs. outer hair cells?
- Inner hair cells = type I afferents
- Outer hair cells = type II afferents
The Dorsal (posterior) cochlear nuclei is involved in what process of hearing?
Integrates the acoustic information with somatosensory information for localizing sound (i.e., where the sound is)
The Ventral (anterior) cochlear nuclei is involved in what functions of hearing?
- Begins processing the temporal and spectral features of the sound (i.e., what the sound is)
- Identifying the nature of the sound (i.e., is it someones voice telling me to get out of the way or a car horn)
What is the first site in the brainstem where information from both ears converges; composed of what 2 primary nuclei?
- Superior Olivary Complex
- Medial superior olivary nucleus
- Lateral superior olivary nucleus
What is the function of the medial superior olivary nucleus of the superior olivary complex?
- Generates a map of the interaural TIME differences, which helps localize the location of the sound
- Assuming that most times sound arrives in each ear at different times and microseconds matter!
What is the function of the lateral superior olivary nucleus of the superior olivary complex?
Generates a map of the interaural INTENSITY differences, which helps localize the source of ths sound
What is the function of the inferior colliculus in the localization of sound?
Suppresses information related to echoes, which would interfere with localization and arrives at a final estimation of localization of sound along the horizon
What is the function of the superior colliculus in the localization of sound?
Takes the location data from the inferior colliculus and adds the final dimension (vertical height) to create a spatial map of the sound’s location
The primary auditory cortex (A1) has a tonotopic representation of sounds, which areas are activated by LOW frequency and which are activated by HIGH frequency sounds?
- More rostral (superficial) areas are activated by LOW frequencies
- More caudal (deep) areas respond to HIGH frequencies
The primary auditory cortex (A1) is essential in conscious perception of sound and what other chacteristics of sound map to areas of A1?
- Loudness
- Modulations in volume
- Rate of frequency modulation
- More pure tones
What are some of the areas of the auditory (secondary) association cortex; what is the tonotopic arrangement like; responds to what kind of sounds?
- Multiple areas (i.e., Broca’s and Wernicke’s, etc.)
- Less specifically organized in the tonotopic arrangement
- Thought the respond to more complex sounds (music), identifying (naming) a sound, and speech
The inner ear contains sensory receptors that will tell us about acceleration, which movements are considered angular acceleration?
- Spinning and turning
- Falling forward
- Falling backward
The inner ear contains sensory receptors that will tell us about acceleration, which movements are considered linear acceleration?
- Moving along a line (head’s point of view)
- Horizontally walking
- Vertically jumping
What kind of acceleration do the semicircular canals detect?
- Rotational acceleration
- Anterior: falling forward
- Posterior: falling backward
- Horizontal: spinning and turning
The utricle is best situated to detect what motion?
Linear acceleration in the horizontal plane
The saccule is best situated to detect what motion?
Detects vertical (up and down) = linear acceleration
The horizontal (aka lateral) canals are best situated to detect which motion?
Rotation in the horizontal plane (spinning) = angular acceleration
The posterior semicircular canal is best situated to detect and maximally activated by which motion?
Rotation in the vertical plane backwards (falling backwards) = angular acceleration
The anterior semicircular canal is best situated to detect and maximally activated by what motion?
Rotation in the vertical plane forwards (falling forward) = angular acceleration
What is the fluid found inside the vestibular apparatus and the fluid surrounding the vestibular apparatus?
Endolymph (high [K+]) resides inside the vestibular apparatus
Perilymph (high [Na+]) surrounds the vestibular apparatus
What is the structure in the Semicircular Canals of the Vestibular Apparatus that is specialized for the process of helping create the excitatory and inhibitory movement of hair cells?
The ampulla
What are the structures in the Utricle and Saccule of the vestivular apparatus that is specialized for the process of helping create the excitatory and inhibitory movement of hair cells?
Otolith organs (ear stones) and the Macula
If the anterior semicircular canal is active (aka you’re falling forward) which eye muscle is activated/inhibited and why?
- The superior rectus m. is activated, while inferior rectus m. is inhibited
- Allows eye to move UP to continue focus as you fall forward
If the posterior semicircular canal is active (aka you’re falling backwards) which eye muscle is activated/inhibited and why?
- The Superior Oblique m. is activated and the Inferior Oblique m. is inhibited
- Eyes will move DOWN to continue focusing on a point as you fall backward
If the horizontal (lateral) semicircular canal is activated (aka you’re spinning), which muscles are activated/inhibited and why?
- The medial rectus m. is activated while the lateral rectus is inhibited (in eye ipsilateral to the rotation)
- The contralateral eye activates the lateral rectus m. and inhibits the medial rectus m.
- Eye moves in a direction opposite the rotation, allowing you to continue to focus as you spin
The vast majority of the cortical and cerebellar involvement in the integration of vestibular information and the control of gaze (vestibulooptic reflexes) is to?
To suppress the reflex to ALLOW for voluntary motion!
