Hearing Flashcards
What is the name of the outer ear?
Pinna
Which membrane is vibrated when sound eaters the ear canal? What 3 parts of the ear are then oscillated?
Tympanic membrane
- Malleus
2, Incus - Stapes
What causes a standing wave in the basement membrane?
Vibration of fluid in the cochlea
How is endolymph different to other external fluids?
High in potassium
How is the sound signal initiated in the organ of Corti?
“Sensory hairs” contain ion channels which are opened by movement and give rise to depolarisation of the hair cells and initiation of the “sound signal”.
Describe the basic ear system in fish
Have neuromast organs that detect pressure waves in the water
Can large animals hear high or low frequencies?
Low - the bigger the animal the lower the frequency
How do low and high frequencies affect behaviour?
low frequencies are suppressive, high frequencies tend to be alerting and stimulating
How does the cochlea work to pick up different frequencies?
It spirals and increases in thickness towards the centre, as it gets thicker it picks up decreasing frequencies
Why can a small animal not pick up low frequencies?
A smaller animal will not have a bit of cochlear that is thick enough to pick up low frequencies
What is meant by the characteristic frequency?
The frequency at which neurons fire most rapidly/easily
Where are low frequencies detected?
Around the thick part of the basilar membrane at the (thin end) apex of the cochlea
What is phase locking?
At low frequencies, neurones “phase-lock” at the same frequencies as the incoming sound wave. This means that they fire action potentials in sync with the peaks of the sound wave
What is tonotopy?
At high frequencies the brain detects that the thin end of the basilar membrane is vibrating, thus the animal is hearing a very high pitched sound
During conducting deafness why may sound not be able to pass into the ear?
- Tumours
- Perforation of ear drum
- Outer and middle ear infections
- Wax build-up in ear canal
- Ear mites
During nerve deafness why may nerves associated with the ear not function?
- Genetics
- Inner ear infections
- Drug toxicity (antibiotics)
- Noise trauma
- Age-related degeneration
Which cranial nerve is involved in the auditory pathway?
VIII
Where are auditory reflexes dealt with in the brainstem?
Inferior colliculus
What are the 2 methods of distinguishing the location of a sound?
- Time delay - arrives at one ear first
2. Volume differences - louder at one ear
Where in the thalamus is the auditory part located?
Medial geniculate nucleus
