Sound Pathway
Malleus, incus, stapes.
Which outer ear structure funnels sound waves into the auditory canal and helps with sound localization?
The pinna.
After the auditory nerve, where is the primary destination in the brain for processing sound?
The auditory cortex found within the temporal lobe.
What does the amplitude of a soundwave change in our perception of a sound?
The loudness.
Pinna -> Ear canal -> Eardrum/Tympanic membrane -> Ossicles -> Oval window -> Cochlea -> Auditory Nerve.
What are the three ossicles? What do they do?
They are small bones called the malleus, incus, and stapes. The three bones amplify vibrations from the tympanic membrane before transmitting them to the inner ear.
Which cranial nerve is responsible for transmitting electrical signals from the cochlea to the brain?
The vestibulocochlear nerve.
What receptor cells are found in the auditory system?
Hair cells in the cochlea.
What happens when sound waves hit the tympanic membrane?
The sound waves cause it to vibrate, which then sends the signal to the ossicles.
What is the organ of corti?
The organ of corti is a structure located within the cochlea that contains hair cells which convert the mechanical vibrations into neural signals.
Before reaching the cortex, auditory information must pass through what major sensory relay station in the thalamus?
The medial geniculate nucleus --> MGN.
Humans can hear from 20-20,000Hz, but they are most sensitive to frequencies between 2000-4000Hz. What important sounds fall within this range that may be the reason for this sensitivity?
The sounds found in human speech.
What is the cochlea divided into?
Scala Vestibuli (transmit soundwaves) , Scala Tympani (transmits soundwaves), Scala Media (converts vibrations to nerve impulses), Basilar membrane (percieves the pitch/frequencies of a sound), Organ of corti (turns sound vibrations into electrical signals).
Name each structure in the three sections of the ear (outer, middle, inner).
Outer ear: pinna, and external acoustic meatus
Middle ear: Tympanic membrane/eardrum, and 3 ossicles
Inner ear: Cochlea, basilar membrane, organ of corti, 3 semicircular canals, and vestibule.
To ensure sound signals travel quickly to the brain, the auditory nerve uses a high length constant (λ). What are two physical ways to increase λ to speed up signal conduction?
Increase the axon diameter (lower internal resistance), and myelination (increase membrane resistance).
As humans age, why do they hear less of high pitched frequencies?
Hair cells for high frequencies are found at the base of the cochlea and hair cells for low frequencies which are at the apex of the cochlea. High frequency hair cells wear out quicker, as they move for both high and low pitched sounds, while low frequency hair cells only move for low pitches.