Exam 2: Hearing Flashcards
Hearing slides for Exam 2 (44 cards)
1
Q
Structure of the external ear.
A
- Auricle
2. Ear canal
2
Q
Structure of the middle ear.
A
- Tympanic membrane
- Malleus, incus, stapes
- Oval window
Bones act as a damper or amplifier for force/energy of volumes
3
Q
Structure of the inner ear.
A
Cochlea (looks like snail shell, sense organs reside here)
4
Q
What are the two fluid-filled canals and where?
A
- Oval window at base of scala vestibuli
2. Round window at abase of scale tympani
5
Q
What are the scala media in between?
A
- Vestibular membrane separates from scale vestibuli
- Basilar membrane separates from scale tympani
- Organ of corti on basilar membrane
6
Q
Describe the capture of sound.
A
- Pressure fluctuations in air move tympanum.
- Movement of tympanum moves auditory ossicles.
- Movement of stapes moves oval window
- Movement of oval window generates “waves” in the fluid filled scala vestibuli
- Motion distorts basilar membrane
7
Q
Is the basilar membrane uniform in length?
A
No, broader at base, more taught at base.
8
Q
What is tonotopic mapping?
A
Mapping sounds to certain areas of the brain. (Frequencies mapped to certain areas of the brain)
9
Q
What is the range of hearing?
A
20 Hz - 20 kHz, arrayed along length of basilar membrane.
10
Q
Complex sounds _____ to frequency components.
A
deconvoluted (simplified)
11
Q
Describe the Organ of Corti.
A
- Contains ~16,000 hair cells/ear (inner and outer hair cells)
- Movement of basilar membrane distorts hair cells, causing depolarization or hyper polarization of receptors.
- Each hair cell maximally sensitive to particular frequency
12
Q
Explain sound transduction.
A
- Mechanical strain to inner hair cells in organ of Corti transduced into electrical potentials.
- Neurotransmitter release encodes intensity, timing, and frequency.
13
Q
Describe hair cells.
A
- Body is surrounded by supporting cell
- 20-300 stereocilia
- 1 kinocilium
- Thinner at base
14
Q
Describe stereocilia.
A
- Mechanically gated K+ channels
- Sometimes open at rest
- Deflection affects open state of channels
- Only sensitive along 1 axis
- Graded response to stimulation
15
Q
Describe the steps for mechanical gating.
A
- Movement towards tall end opens more channels
- Movement towards short end opens fewer channels
- Open more quickly than other sensory receptors due to the use of ion channels
16
Q
Describe hair cells tuned to frequency.
A
- Cells sensitive to low frequency have long stereocilia bundles.
- High frequency have SHORT stereocilia bundles
- Cells most responsive when stimulus frequency matches membrane frequency
- Affected by kinetics, # of Ca2+, K+ channels, time it takes to remove Ca2+ from cell
17
Q
How are hair cells highly sensitive?
A
- Modulation occurs at very small changes in membrane potential: small change = big change
- Must be able to release large numbers of vesicles quickly, possibly associated with presynaptic dense bodies.
18
Q
How does the cochlea amplify signal?
A
- Most sound energy goes to moving fluid, not deforming hair cells.
- Cochlea much more sensitive at LOW intensity sound than high intensity (volume selective switch).
19
Q
Describe the spiral ganglion.
A
- Curves around the core of cochlea.
- Majority (90%) of input from inner hair cells
- Encodes stimulus intensity and frequency
- Linear relationship between sound intensity and firing rate: as volume increases, firing rate increases
- Frequency encoded by place and neurons fire in-phase with sound.
20
Q
What is the auditory pathway?
A
Spiral ganglion -> CN 8 -> cochlear nuclear complex at medulla-pons junction
21
Q
What does the anteroventral cochlear nucleus do?
A
No job
22
Q
What does the posteroventral cochelar nucleus do?
A
- Encodes frequency
2. Sound localization in horizontal plane
23
Q
What does the dorsal cochlear nucleus do?
A
- Layered (like the cortex)
- sound localization in vertical plane
- Suppresses echoes
24
Q
Where are signals the strongest?
A
To the contralateral side of the brain
25
How is sound localized?
1. Anteroventral cochlear nucleus projects to medial olive where the olive receives bilateral input to be able to do sound localization.
2. Localization based on inter aural timing differences
3. Lateral superior olive uses inter aural intensity differences to localize.
26
What do the coincidence detectors show about sound localization?
Need co-occurring stimulus to trigger action potential. This allows us to localize where sounds come from in a room/from which ear.
27
How is the inferior colliculus involved in hearing?
Receives projections from olive via lateral lemniscus (pathway from olive to inferior colliculus)
- Central nucleus has tonotopic map
28
What is the function of the superior temporal gyrus?
Part of primary auditory cortex
| - Detect sounds based on frequency (high and low) temporal lobe R to L.
29
What does Heschl's gyrus do?
Part of the primary auditory cortex: Area that detects talking as human speech, left hemisphere of the human brain.
30
Describe the vestibular system.
Located in the inner ear, responsible for the balance and equilibrium in relation to motion.
31
How does the vestibular system work?
Movement or acceleration of head causes deflection of hair cells.
32
Describe the two types of linear acceleration.
Utricle: horizontal motion
Saccule: vertical motion
33
Describe angular acceleration (semicircular canals).
3 canals responsible for different angles of acceleration: Front flips, cart wheels, spinning around in circles.
34
Describe the hair cells in linear acceleration.
1. Localized in macula (utricle+saccule)
2. Top attached to otolithic membrane (rock in ear that acts like a level and bubble in liquid)
3. During motion, membrane moves after skull causing deflection of hair cells.
4. Different hair cells oriented to be sensitive to acceleration in different directions.
5. Degree of acceleration signaled by graded response
35
What's an example of how the fluid in the ampulla affects the cupula, hair cells, and sensory nerves?
As you turn your head, the fluid will remain still in the ampulla. Causes hair cells in cupula to turn accordingly to the force/direction the cupula is pushed by the fluid.
36
What is the striola and where is it located?
In utricle hair cells and is where the direction of the hair cells change.
37
What is the endolymph for and where?
1. Found in the semicircular canal (angular acceleration) and moves in the opposite direction of the head.
2. Movement of endolymph pushes on cupula, distorting hair cells.
38
What does the horizontal semicircular canal help with?
Helps subtract movement of your head (uses ion channels for fast detection/response) and helps eyes remain focused on the same spot.
39
What are the functions of vestibular reflexes?
1. Monitors body movement and position
2. Stabilize eyes when head moves (signals speed and direction of movement)
3. Quick response time helps maintain posture
40
What is the vestibular pathway?
1. Vestibular nerve projects to vestibular nuclei in medulla and pons.
2. Integrated with information from spinal cord, cerebellum and visual system.
3. Projects to oculomotor nuclei, skeletal movement nuclei, cerebellum, thalamus.
41
What is the superior and medial subareas responsible for?
Subareas of Vestibular nuclei.
1. Input from semicircular canals
2. Project to oculomotor nuclei and spinal cord
3. Inhibitory and excitatory, respectively.
42
What is the lateral subarea responsible for?
Subarea of Vestibular Nuclei.
1. Input form semicircular canals and otoliths
2. Projects to vestibulospinal tract for posture
43
What is the descending subarea responsible for?
Subarea of Vestibular nuclei
1. Input from otoliths
2. Projects to cerebellum, brain stem, spinal cord, contralateral vestibular nuclei
3. Integrates vestibular information with motor planning
44
The subareas of Vestibular Nuclei all project to what?
1. Ventral posterior and ventral lateral nuclei of thalamus
2. Project to BA 2V, 3A, secondary somatosensory and parietal association areas (BA 7): all involved in sensory perception.
