Ear Part 2 Flashcards
What is the frequency of perceived sound determined by?
By which part of the cochlear duct is stimulated the most
What is intensity of perceived sound determined by?
It’s determined by the number of hair cells stimulated in that location
What does sound consist of?
Waves of pressure through a medium such as water or air
What do pressure waves consist of ?
Regions where air molecules are crowded together and adjacent zones are where molecules are farther apart
What are Sine waves?
S shaped curves that travel the air at about 1235km/h
What is a wavelength?
Distance between two adjacent troughs/crests and inversely related to the frequency
What is frequency?
The number of waves that pass the reference point in a given period of time
What is the pitch of sound?
Our sensory response to frequency of sound (the higher the frequency the shorter the wavelength)
What is sound energy reported in?
Decibels
What is amplitude?
It’s the intensity of sound
What is the process of hearing?
The sound wave arrives at the tympanic membrane, as it enters the external acoustic meatus and the orientation of the auditory canal provides directional sensitivity
When the tympanic membrane moves it displaces the auditory ossicles and the tympanic vibrates also causing the ossicles to vibrate and this is how sound is amplified
What happens when the stapes moves inward?
The basilar membrane distorts towards the round window and it is pushed outwards and thats how sound is processed and bulges into the middle ear cavity
What happens when the stapes moves outward?
The basilar membrane rebounds and the oval window is distorted and the round window moves inwards and dissipates excess energy to the cochlear fluid
What happens when there is movement of the stapes at the oval window?
It creates pressure waves in the perilymph of the Scala vestibular as liquids aren’t compressible
What do the inner hair cells of the organ of Corti do?
They convert slund vibrations to neural signals through the steering action of their stereocillia
What do the outer hair cells do?
They function as acoustic pre amplifiers which improve frequency selectivity by allowing the organ of Corti to become attuned to specific frequencies
What do pressure waves do?
They distort the basilar membrane on their way to the round window of the scalar tympani
What does vibration of the basilar membrane cause?
It causes vibration of hair cells against the tectorial membrane
Where is information relayed?
It is carried by the cochlear branch of the cranial nerve VII to the cochlear nuclei of the medulla oblongata to other centers of the brain
What is signal generation?
When the basilar membrane moved upwards and reticular membrane and sterocillia bends outwards and produces a receptor Potential this depolarization allows for CA to enter which in turn results in the release of NT The NT will stimulate the sensory neuron auditory fibers to send signals to CNS
Which nerve is cranial nerve VII?
The Vestibulocochlear nerve
What Is the auditory pathway?
Where stimulation of hair cells with activate sensory neurons which cell bodies are in the adjacent spiral ganglion and the affarent fibers of the neurons from the cochlea branch VII
The axons enter the medulla and synapse at the dorsal and ventral cochlear nuclei and the information will cross to the opposite side if the brain and move up to the inferior colliculus of the midbrain
Where do ascending auditory sensations synapse?
Medial geniculate nucleus of the thalamus
What are effects of aging on the ear?
The typanic membrane gets less flexible
Articulations between the ossicles stiffen and the round window May begin to ossify
What are the 3 types of hearing loss?
Conductive
Sensorineural
Mixed
What is conduction deafness?
When there is a wax build up or damage to the eardrum
What is sensorineural deafness?
Age or noise related damage to the cochlea and degeneration of the cochlea nerve
What Is mixed deafness?
Combination of sensorineural and conductive
