Week 3 lectures (hearing and vision) Flashcards
What the the stages of the process of perception
- sensory signal
- travels to sensory receptors
- Combine past experience and attention to create a
- Percept
- which leads to a perceptual understanding
- Which leads to a behavioural response
How does the amplitude of the sound wave affect the sound?
greater amplitude=larger sound
From what decibels can humans hear sounds?
0-140db
From what Hz can humans hear sounds?
20Hz to 20KHz
How does the frequency of the sounds wave influence the sound?
Higher frequency= higher pitch
Whats the outer ear consist of?
The stuff we can easily see and touch
the pinna/auricle
the external auditory canal
What is the tymphanic membrana also known as?
The eardrum
Which parts of the ear does the tymphanic membrane seperate?
The outer ear from the middle ear cavity
How many bones does the middle ear cavity have and what are they called?
malleus
incus
stapes
Where are the Auditory hair cells?
Cochlear
Where are the stapes?
In the middle ear, at the entrace to the cochlear
What to the stapes do?
The stapes are bones which move in a lever like direction to transmit information from the middle ear to the cochlear
What two types of hair cells are in the cochlear?
The inner hair cells (main hair cells involved in detecting auditory stimuli)
the outer hair cells (plays a role in amplifying signals)
what two nerves in the ear come from the cochlear and combine to form one of the cranial nerves?
the cochlear nerve
the vestibular nerve
What are 4 functions of the outer ear?
Funnels sound inwards
amplifies the sound by acting as a tube for it to echo in
Shape of the pinna Helps sound localisation in the vertical plane
protection: earwax is water resistant, antibacterial and antifungal
the outer ear has an acidic environment
hairs in the outer ear prevent entry
What are two functions of the middle ear?
- protection- middle ear reflex can lock position of bones to prevent transmission of loud sounds
- Acoustic impedance matching- amplifies pressure created by sound wave to prevent loss of signal as it eners fluid filled cochlear
(when sound travels from air filled middle ear to fluid filled cochlear some sound waves are reflected back, meaning signal is lost. The shape of the middle ear increases the pressure created by the sound wave to prevent loss of signal)
what is 1?
pinna
what is 2?
malleus
what is 3?
The incus
What is 4?
The semicircular ducts
What is 5?
The vestibular nerve
What is 6?
The cochlear nerve
What is 7?
The cochlear
What is 8?
The auditory tube
What is 10?
The stapes
What is 11?
The tympanic cavity
What is 12?
The eardrum
What is 13?
The auditory canal
Where in the cochlear are the inner hair cells located?
in the organ of corti
The inner hair cells have ‘hairs’ of varying lengths, what are they called and what is the tallest one called?
The stereocilia
The tallest is the kinocyleium
What happens when the stereocilia bend towards the kinocyleium?
The cell becomes excited
What happens when the stereocilia bend away from the kinocyleium?
The cell is inhibited
When the stereocilia are at rest, what is going on with the k+ gated channels on the stereocilia?
The channels are shut, so no ions can move into the stereocilia
What are two types of gated channels on an inner hair cell?
Mechanically gated k+ channels on the stereocilia
Voltage gated calcium channels on the main cell body
What neurotransmitter does the inner hair cell contain vescicles of?
Glutamate
What receptor does the postsynaptic neuron in the auditory nerve, connecting to the inner hair cell contain?
AMPAr receptors (glutamate receptors)
What happens in the inner hair cell at the arrival of a soundwave?
- the soundwave causes fluid in the stereocilia to move
- this causes the stereocilia to move in the direction of the kynocilium
- This physically opens the mechanically gated k+ channes
- There is a high concentration of k+ outside of the cell, so k+ moves into the inner hair cell through the channels (down the concentration and electrostatic gradient)
- The charge of the cell becomes more positive leading to depolarisation
- The depolarisation opens the voltage gated calcium channels and calcium ions flood in
- This triggers vescicles of glutamate to be released
- glutamate binds to the receptors on the auditory nerve and excites the cell so it triggers an action potential
What type of potential does the hair cell have (instead of an action potentail?)
A receptor potential
What is the auditory pathway from the cochlear to the brain?
Cochlea
Cochlear nuclear complex (brainstem)
Superior olivary complex (brainstem)
Inferior colliculus
Medial geniculate nucleus (thalamus)
primary auditory cortex
At what level of the auditory pathway is information from both ears combined into both areas of the brain?
The superior olivary complex (brainstem)
What are two ways that the brain can deduce frequency of a sound wave?
Place code
Rate code
What is place code?
- specific hair cells in the cochlear respond to specific frequencies
- The hair cells then excite specific auditory nerve cells
- They have a tonotopic relationship meaning that two hair cells next to each other will activate two nerve fibres next to each other
- There is a specific mapping of the hair cells and nerve cells all the way up the pathway.
- The brain uses this specific mapping to deduce the frequency of the sound wave
What is rate code?
- Hair cells oscillate at the frequency of the sound wave
- this means the neurotransmitters are released at the frequency of the sound wave
- This means that the frequency of the auditory nerve potential is the same frequency of the sound wave, this is known as phase locking
What is volley theory?
- The brain can hear sounds at a higher frequency that neurons can fire
- It is thought that multiple neurons can fire as a volley to later combine and equal the frequency of the original stimulus
- This process allows phase locking even at higher frequencys
Is place code better for lower or higher frequencies?
Higher frequencies
Is rate code better for lower or higher frequencies?
lower
What are two ways the brain can deduce the intensity of a sound?
- from the frequency of the firing in the auditory nerve
- from the number of neurons firing
How does the brain deduce the intensity of a sound from the frequency of the firing in the auditory nerve?
- Louder sounds have a greater amplitude of sound wave
- This creates greater movement in the cochlear, bending the stereocilia more
- This causes a greater influx of K+ ions, leading to greater calcium influx and glutamate release
- More glutamate release increases chance of binding to receptors and causing EPSP
- Action potentials cannot get bigger with more ESPS’s but they get created more often