Section 1.1 Outer Ear Flashcards
What is Resonance?
Phenomenon that amplifies a vibration.
Vibration is transmitted to another object whose natural frequency is at or very close to the source’s.
What are the main structures for the pathway from the peripheral to the central nervous system? (7)
External ear, Middle Ear, Basilar Membrane, Receptor Cells, Auditory Nerve, Brainstem, Cortex
What of are the functions of the EE structure?
Gather/Reflect and conducting sound protect eardrum.
What of are the functions of the ME structure?
Conducting/modification of sound protect cochlea against loud sound
What of are the functions of the Basilar Membrane structure?
Filtering (frequency analysis)
What of are the functions of the Receptor Cells structure?
Signal Transduction
What of are the functions of the Auditory Nerve structure?
Simple coding (transmission) convert the signal into readable for the cortex
What of are the functions of the brainstem structure?
Complex Coding, feature abstraction.
What of are the functions of the Cortex structure?
Perception
What is the nature of the signal processing at EE step?
Mechanical
What is the nature of the signal processing at ME step?
Mechanical
What is the nature of the signal processing at Basilar Membrane step?
Mechanical to Hydrodynamics
What is the nature of the signal processing at Receptor Cells step?
Mechanical to Electrochemical
What is the nature of the signal processing at Auditory Nerve step?
Electrochemical
What is the nature of the signal processing at Brainstem step?
Electrochemical
What is the nature of the signal processing at Cortex step?
Electrochemical
Describe the change that occurs in the way sound travels once it goes from the external ear to the inner ear (hint: impedance).
Sound is passing through fluid in IE.
Compared to air, there is much greater impedance in fluid (mechanical hydrodynamics). There is therefore a loss of energy (33 dB) from the impedance mismatch. In the middle ear, the sound is amplified to accommodate for this.
What is transduction (and steps) and what is it specific to the auditory system?
Mechanical signal is converted to electrical signal (receptor potential) at the top of the hair cells (via the MET channel).
What is included in the peripheral auditory system?(3)
External Middle and inner ear
what is included in the central auditory system? (4)
Auditory brainstem, mid-brain, Thalamus, Cortex
What is at the border PAS and the CAS?
Auditory nerve
What are the shapes of the external, middle and inner ear?
External ear shape: S shape
Middle ear: Cubic
Inner ear: Snail Shape
What is a unique feature of the auditory peripheral organ?
The structural features of the auditory peripheral organ are closely related to their functions.
What do the external, middle and inner ear contain?
External ear: Hairs, Wax
Middle ear: Bone chain, ligaments and muscles.
Inner ear: Cochlea semi-circular canals
What are the 4 main functions of the external ear canal (briefly)?
- Gathering/conducting sound
- Signal processing: ear canal resonance modifies sound in frequency and amplitude (Especially in high frequencies)
- Provide cues for localization
- Protect against foreign bodies
Where does the ear lobe block more sound from (i.e., which direction)?
From behind
What are examples of foreign bodies that the external ear canal provides protection from?
Insects, qtips, Toys
What are the THREE main middle ear functions?
- Sound conduction from eardrum to inner ear via bone chain
- Impedance match by amplification
- Protect IE from loud noises
What is impedance?
resistance to displacement
What are the three components of Impedance?
Mass, Stiffness and Resistance (friction)
What and why is their impedance matching?
ME transfers incoming vibration from larger, low impedance tympanic membrane to much smaller, high impedance oval window. If not there would be a 33dB loss.
What is the difference in what the middle ear is protecting compared to the external ear canal?
ME protects against loud sounds EE protects against foreign objects.
What does the eustachian tube balance? What happens if it is unbalanced?
Balances air pressure in the ME. Distorted hearing, muffled sounds, ear pain.
What are the 4 functions of the cochlea (for hearing)?
- Converting Acoustic signal to biochemical-electrical signals-by receptor sensor cells
- Frequency processing-
- Encoding of sound features to action potential in auditory nerve neurons
- Feedback control