Overview of the auditory system Flashcards
Describe the development of sensing sound over evoultion
- First amphibians had some sensory cells - sense the movement of water around the body
- As move out of water onto land - evolutionary pressure to sense sounds carried by the air
- Evolved massive range of frequency and intensity sensitivity
- Lead to the formation of the tympanic ear
What is important about the evolution of the tympanic ear?
Appeared 3 times over evolution, in:
- Mammals
- Amphibians
- Birds
Shows that this structure is very important
What is sound frequency?
What is it measured in?
- Amount of waves per second
- The pitch of sound
Measured in Hz
How are wide ranges of sound frequency detected?
By the cochlear mechanics and physiology of the hair cells
What is sound intensity?
What is it measured in?
The volume of the sound
Measures in dB
How are wide ranges of sound intensity detected?
By the firing rate of many afferent nerve fibres that innervate the hair cells of the cochlea
What is a rapid onset of sound important for?
Localising different sounds
and
Creating a topographic map of the auditory sound in the brain
How are the sensory cell synapses of the auditory system different to conventional synapses?
Why?
They are specialised for sustained neurotransmitter release
So that the ear remains sensitive to sounds constantly
Describe the pathway for sound from the outer ear to the cochlear
- Auricle funnels the sounds into the ear canal
- Vibrates the tympanic membrane
- Vibrates the ossicles, which transmit the vibration of the tympanic membrane to the round window
- Causing a vibration of fluid in the cochlear
What is the auricle of the ear?
What does it do?
The external, visible part of the ear
Shapes the sounds and funnels them into the ear canal
What is another name for the tympanic membrane?
The ear drum
What are the ossicles of the ear?
Why are they necessary?
Malleus, Incus and Stapes
- Transmit the sound induced vibration of the tympanic membrane to the fluid movement in the cochlear
- To AMPLIFY the movement of air
What would happen if the ossicles were not present
Air would bounce off the round window
What is contained in the middle ear?
Tympanic membrane
Ossicles
What is contained in the inner ear?
Cochlear
Vestibular organs
What are vestibular organs important in?
Balance
What are the vestibular organs?
- Semi-circular canals
- Utricle and saccule
What are the chambers of the cochlear? (base to apex)
Scala Tympani
Scala Media
Scale Vestibuli
What is the scala media also called?
The cochlear duct
What is the cochlear innervated by?
Where does it enter the cochlear?
What does it innervate?
The cochlear nerve (VIII)
Enters the cochlear through the core (modiolus)
Innervates the organ of corti
Where are the cell bodies of the neurons in the ear?
In the spiral ganglion
Where are the sensory cells are the ear?
In the organ of corti
Which chamber/s of the ear contain endolymph?
Scala media
Which chamber/s of the ear contain perilymph?
Scala tympani
Scala vestibuli