PNB 2XB3 - Auditory System Questions And Answers Already Graded A+
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Module
PNB 2XB3 - Auditory System
Institution
PNB 2XB3 - Auditory System
Higher pitch = - ️️higher frequency - but perception depends on the environment
Wavelength - ️️the distance b/w two peaks/an up-down cycle
Middle ear - ️️everything inside the tympanic membrane and before the oval
window
LSO - ️️- monitors intensity differences for high-frequenc...
PNB 2XB3 - Auditory System
Higher pitch = - ✔️✔️higher frequency - but perception depends on the environment
Wavelength - ✔️✔️the distance b/w two peaks/an up-down cycle
Middle ear - ✔️✔️everything inside the tympanic membrane and before the oval
window
LSO - ✔️✔️- monitors intensity differences for high-frequency sound
- head blocks frequencies that have wavelengths smaller than the head - produces a
sound shadow (in humans - higher than 2kHz)
- the ipsilateral LSO starts firing more when there is a sound on that side - also activates
the contralateral MNTB - another nucleus that axons decussate to - MNTB interneuron
releases inhibitory neurotransmitters onto contralateral LSO
- therefore we can localize sound b/c LSO excitation will be greater than inhibition of
that same LSO from MNTB
Ascending auditory pathway - ✔️✔️- cochlear nerve: where sound transduction
happens
- 8th cranial nerve/auditory nerve: nerve goes up the brainstem and enters the rostral
medulla
- medulla has 2 nuceli: dorsal cochlear nucleus (has axons that decussate at the
medulla and go to the midbrain; midbrain axons go to the auditory/medial geniculate
thalamus); ventral cochlear nucleus (has axons that go to the pons - next most rostral
part of the brainstem)
- axons terminate bilaterally - affect both hemispheres (bilateral projections)
Adult human voice - ✔️✔️- has multiple tones - but there are dominant frequencies
- the avg male voice = 100 Hz (11 foot wavelength)
- the avg female voice = 200 Hz (6 foot frequency)
Period - ✔️✔️the time taken for one up-down cycle (wavelength)
Sound frequency - ✔️✔️- longer wavelengths = lower frequency
, - basilar membrane is like a xylophone in our ears
Sound waves are ___; compression is __ of a wave, rarefaction is ___ -
✔️✔️longitudinal - move like a slinky; top; bottom
Sound localization - ✔️✔️- humans are very good at this; use 2 cues:
- the loudness (if its louder in the left ear, it is coming from the left); the time (if it's
coming from the right it arrives to the right ear first)
- neurons on either side compare these things
Auditory Cortex - ✔️✔️- there is tonotopic representations - different frequencies
activate different neurons in the auditory cortex (like visuotopic representation)
- higher frequencies correspond with base of cochlea
- lower frequencies corresopnd with apex of cochlea
- humans can hear between 20-20000 Hz
The superior olivary complex contains 2 nuclei for sound localization - ✔️✔️lateral
superior olive (LSO) and medial superior olive (MSO)
As sounds get closer to the face, ___ - ✔️✔️both LSOs start firing more equally
MSO - ✔️✔️- monitors interaural time difference for low frequency sounds
- low frequencies have wavelengths longer than the diameter of the head (>2kHz) - they
don't produce a sound shadow; diffract around the head
- sounds coming directly from the side have the greatest time delay, then from an angle,
then straight on have no time delay
- MSO acts as a coincidence detector - depending which axons from each ear are firing
at the same time, it can infer which side the sound is coming from (i.e. if the ones firing
at the same time are farthest from the left and closest to the right, sound is coming from
the left b/c it got a head start)
The human ear - ✔️✔️- sound funnels into the canal and eardrum (tympanic
membrane)
Ossicles - ✔️✔️- malleus, incus, stapes
- they are the smallest bones in the body- they vibrate which causes the fluid in the ear
to vibrate and causes events called transduction
Oval window and round window - ✔️✔️are connected, if one is pushed then fluid
bulges out of the other
Tensor tympani and stapedius muscle - ✔️✔️- are muscles connected to the ossicles;
when these muscles contract, it stops the vibration of the ossicles
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