Auditory System Flashcards
What is the adequate stimulus for the auditory system?
Sound pressure waves
What type of stimulus is sound and what is the receptor which detects it?
Sound is a mechanical stimulus perceived by the mechanoreceptor hair cells which synapse onto primary afferents.
How does the tympanic membrane amplify sound? How does this compare to if sound waves were to directly hit the fluid filled system?
The tympanic membrane causes vibration of the ossicles in the middle ear which transfer vibration to the perilymph of the inner ear. This allows for a transfer of 60% of the vibratory energy compared to 0.1% if the sound waves were to hit the fluid directly.
Describe primary afferents of the central auditory pathway
Primary afferents have axons which receive signals from hair cells. Cell bodies lie in the spiral ganglion within the modiolus and project the cochlear nuclei.
Describe secondary afferents of the central auditory pathway.
Secondary afferents run from the cochlear nuclei to the superior olivary nucleus bilaterally via the trapezoid body.
Describe tertiary afferents of the central auditory pathway.
Tertiary afferents run from the superior olivary nucleus to the ipsilateral inferior colliculus via the lateral lemniscus. Inferior colliculi communicate bilateral.
Describe quaternary afferents of the central auditory pathway through the primary auditory cortex.
Quaternary afferents will synapse at the medial geniculate nucleus, which serves as the thalamic auditory relay, through the brachium of the inferior colliculus. Fifth order neurons in the medial geniculate nucleus project to the primary auditory cortex.
What is the primary auditory cortext (anatomical and histological designations)?
Transverse temporal gyrus
BA = 41, 42, 22
How does sound localization occur (2)?
- Inter-aural sound intensity due to an acoustical shadow cast by the head
- Inter-aural delay which is processed by the superior olivary nucleus
Describe the cochlear amplifier.
Outer hair cells will shorten when depolarized. This will amplify the vibrations of the basilar membrane of the cochlear duct increasing the sensitivity of inner hair cells.
What is aphasia?
Disturbance in the use of language.
What is receptive aphasia?
Also known as Wernicke’s aphasia. Motor components such as grammar, rhythym, and melody are normal, but there is no meaningful content to the patient’s speech.
What is expressive aphasia?
Also known as Broca’s aphasia. Impairment of the motor components of speech. A patient is able to comprehend, but unable to find the right words they want to communicate.
