Auditory Flashcards
What are the major landmarks of the auricle?
Made up of Elastic cartilage covered with skin, Sebaceous glands associated with hairs
Landmarks: Helix & antihelix
• Tragus & antitragus
• Concha & lobule
Where are the ceruminous glands and what do they produce?
Modified apocrine glands –> protects ear canal against
damage and bacteria.
What nerves innervate the inner and outer surfaces of the tympanic cavity?
EAM sensory: Greater auricular (GA) • Lesser occipital (LO) • Auriculotemporal, V3 (AT) • Facial (VII) • Vagus (X) Middle ear: glossopharyngeal (IX)
. Describe the Eustachian tube and what muscles open it. ?
connects tympanic cavity to nasopharynx.
– Tubal cartilage: opened by levator/tensor palati,
salpingopharyngeus
How does swallowing equalize pressure in the middle ear?
it opens the eustachian tube allowing pressure to equalize
Describe the ossicles, their attachments and their significance in transmission of sound.
Function: Amplifies vibrations from wide tympanic
membrane through narrow base of stapes.
Malleus: attached to tympanic membrane
Incus: transmits malleus–>stapes
Stapes: attached to oval window–>cochlea
Where are the tensor tympani and stapedius muscles, to what do they attach and what do they do?
Muscles that dampen ossicle movement
Tensor Tympani dampens extreme low
frequency vibrations ; innervated by V3, MALLEUS
Stapedius dampens extreme vibrations of STAPES; innervated by VII
Describe the chorda tympani in terms of: source, how it passes through the tympanic cavity, and its function.
Branches from the Facial nerve (CN VII) in the tympanic cavity, exits and joins V3 as it approaches the oral cavity.
Between tympanic membrane & malleus
Sensory (TASTE ant. 2/3 tongue) and autonomic axons (gsnglions to salivary glands).
Where does otitis media occur?
infection/inflammation of the middle ear. Negative pressure pulls tympanic membrane inward. Chorda tympani can be impacted
What is the tegmen tympani and its significance in spread of infection?
a THIN plate of bone that covers the middle ear and separates it from the cranial cavity. Infection can perforate
. Describe the spaces in the cochlea.
fluid-filled spirally formed bony canal, contains the membranous cochlear duct that contains the hearing receptors.
– Cochlear duct (scala media)
– Scala vestibuli
– Scala tympani
Describe the cochlear duct in terms of membranes, windows and fluid.
separated from the other spaces by the vestibular and basilar membranes and contains endolymph. Encloses organ of Corti
• Endolymph is secreted by stria vascularis
What is the difference between perilymph and endolymph?
Cochlear duct contians endolymph (high K+); surrounded by perilymph (high Na+)
Perilymph: Located in scala vestibuli and scala tympani
Endolymph: membranous labyrynth
Describe the organ of Corti in terms of location, cell types, relation to the tectorial membrane.
Epithelial layer on the basilar membrane, covered by the
tectorial membrane. Inner and outer layers of non-neural hair cells embedded on the basilar membrane .
Stereocilia contact the overlying tectorial membrane
Hair cells –>sensory neurons of the cochlear/auditory nerve
SANDWICH
inner hair cell in terms of location, function. Innervation, and impact on sound reception?
• primary sensory cells transmitting sound
information to the brain
• 95% of sensory neuron axons in the
cochlear nerve innervate the inner hair
cells (IHC)
• Inner cells respond to basilar membrane
movements at specific frequencies
• Cochlear nerve projects inner cell activity
to cochlear nuclei in the medulla
How does the cochlea encode sound frequencies?
Frequency (pitch) of incoming sound is initially
coded by difference in basilar membrane
stiffness and width from base to apex –> This maximum is the place where the membrane has the physical properties to resonate with vibrations. Sweet spot
What are the major brain stem steps by which sound information reaches the cortex?
Auditory nerve projects from cochlea to dorsa (quality) l and ventral (localization) cochlear nuclei in medulla.
Both sets of medullary auditory nuclei project up
lateral lemniscus -> inferior colliculus -> medial
geniculate -> primary auditory cortex in temporal
lobe
How does the superior olive localize sound?
Ventral cochlear nucleus -> superior olive
(black)
– Localization: disparity in time and intensity
between R & L sounds localizes object in
space.
TIME difference localizes LOW FREQUENCIES
INTENSITY difference localizes HIGH FREQUENCIES
Describe the anatomy and impact of superior olivary feedback onto the organ of Corti.
AUDITORY SELECTIVE ATTENTION
• Efferent olivocochlear neurons from the superior olive terminate on outer and inner HAIR CELLS to regulate their sensitivity and electromotility responses to sound
Olivocochlear efferents inhibit outer cell responses to basilar membrane waves–inhibition at low levels
Describe the location and function of the primary auditory cortex.
Superior temporal lobe
• Tonotopic organization of frequencies is synthesized into sound forms
What is tinnitus? Compare subjective and somatic types of tinnitus.
subjective:sensation of sound without external stimulation. Phantom. abnormal activity in brain stem, primary auditory cortex changes, multiple causes
Somatic:form of subjective tinnitus, is usually triggered by synergistic effects of two or more causes, including
somatosensory stressors
What are the dorsal and ventral streams of cortical processing of auditory information? What are their functions?
Ventral stream: for speech comprehension which flows into the temporal lobe; largely bilateral, Includes Wernicke’s area, angular gyrus
Dorsal Stream:Sensory-motor integration, broaca’s area, left dominant. Localization of sound in body schema
How is music processed in the cortex
Rhythm on left, melody on right.
temporal, parietal and motor cortices all involved bilaterally in higher levels.
Speech, rhythm, and melody use both sides, asymmetrically.
Music activity in auditory cortex can modulate activity in limbic regions involved in emotion (amyg)
What’s the Umbo?
central depression created by tension of the malleus in the tympanic membrane
WHat and where is Cholesteatoma?
skin from the ear canal that fills with cysts and migrates through a perforation in the tympanic membrane. can damage mastoid, inner earf
How does the cochlear duct work?
Membranous tube that encloses the organ of Corti with endo (K) and perilymph (Na). Oval window: base of stapes triggers fluid vibrations in perilymph .Round window: absorbs outward displacements of fluid vibrations
outer hair cell in terms of location, function. Innervation, and impact on sound reception?
mostly do not activate sensory neurons. Mechanical amplifiers for inner hair cells. Outer cell responses are frequency specific.–> positive feedback that
enhances the amplitude of basilar membrane oscillation and inner hair cell responses.
Loud noise kills them!
How are receptor stereocilia activated?
Sound waves make vertical oscillations in the basilar membrane against the tectorial membrane,–>shear forces bend the receptor stereocilia–>s trigger
depolarizations followed by release of transmitters onto
sensory neurons
Where does the Inferior Colliculus get its input from?
Auditory from cochlear nuclei & superior olive
Somatosensory: input associated with
orientation of head and other body regions
for sound localization
What does the Medial geniculate body of thalamus do?
projects sound to auditory cortex tonotopically
