Anatomy & Physiology of the Auditory System Flashcards
What are the anatomical planes?
- Sagittal
- Coronal
- Tranverse or Horizontal
What does sagittal mean?
Planes separates left from right
What doe coronal mean?
Plane separates front to back
What does transverse mean?
Plane separates top from bottom
What are the anatomical terms of location?
- Superior
- Inferior
- Superficial
- Deep
- Dorsal/Posterior
- Ventral/Anterior
- Cranial
- Rostral
- Caudal
- Proximal
- Distal
- Medial
- Lateral
- Unilateral
- Bilateral
- Contralateral
- Ipsilateral
What does superior and deep mean?
Superior: Toward the surface
Deep: Away from the surface
What does cranial, rostral, and caudal mean?
Cranial: Toward the head
Rostral: Toward the nose
Caudal: Toward the foot or base of the skull
What does proximal, distal, medial, and lateral mean?
Proximal: Toward the point where extremity joins the body
Distal: Toward the end of the extremity
Medial: Toward the midline
Lateral: Away from the midline
Explain the difference between sensation and perception.
Sensation is where our senses receive stimuli from our environment and pass the information to our brain.
Perception is the process of our brain organizing and interpreting the sensory stimuli into our conscious as it relates to our everyday lives.
Explain the difference between “bottom-up” & “top-down” as it relates to sensation & perception.
Sensation is a bottom-up process where information comes from the peripheral system (ears, eyes, nose) to the central system (brain).
Perception is a top-down process, where the central systems act on the information it receives from the periphery system.
Name the cranial nerves that innervate sensory portions of the outer and middle ear.
- Vagus X - carries tactile information from the outer ear and ear canal via Arnold’s nerve
- Glossopharyngeal IX: Carries tactile information from the middle ear, tympanic membrane and Eustachian tube
- Vestibulocochlear VIII: Carries sensory information on hearing and balance from the auditory and vestibular portions of the cochlea
- Facial VII: Carries tactile information from pinna and ear canal
- Trigeminal V: Carries tactile information from outer and middle ear
Name the cranial nerves that innervate the muscles of the middle ear
- Facial VII: Inneravates the stapedius muscle of the middle ear via pyramidal eminence
- Trigeminal V: Mandibular nerve innervates the tensor tympani in the middle ear
List out the parts of the outer ear
- Helix
- Lobe
- Anti-tragus
- Tragus
- Intertragal Insisure
- Conca Cavum
- Crus of Helix
- Concha Symba
- Anti-helix
- Scaphoid Fossa
- Triangular Fossa
What are the main cues in the horizontal plane?
- Interaural Timing Differences (ITDs)
2. Interaural Level Differences (ILDs)
What are the cues for sound localization in the vertical plane?
- Monaural Cue
2. Spectral Peaks & Notches
How are our head and ears able to filter sounds differently?
Depending on the incoming angle of the sound towards the head.
How does Interaural Timing Differences help us localize sounds?
Sounds arrive at each of our ears at slightly different times, and our brain interprets ITDs order of milliseconds to localize sound.
How does Interaural Level Differences help us localize sounds?
Sounds are amplified/attenuated to slightly different levels at each ear
What does ILDs help localize?
HFs sounds
What does ITD help localize?
LFs sounds
What does ITDs mean?
Interaural Timing Differences
What does ILDs mean?
Interaural Level Differences
When does Cone of Confusion occur?
When ITDs & ILDs cues are ambiguous
What solves Cone of Confusion?
Sound localization in the vertical plane
What does the pinna provide to help localize sounds in the vertical plane?
Monaural cues
What helps determine the elevation of sound sources?
Spectral peaks & notches
Define spectral peaks and notches?
High/low points that appear at different frequencies depending on how sound hits the pinna
Explain how the shape of the pinna contributes to sound localization
Sounds coming from different angles in the vertical plane bounce off the structures of the pinna in different ways, creating spectral peaks and notches that the brain interprets as cues for localization in the vertical plane. These pinna reflections also help resolve front-back confusions and other ambiguous locations in the cone of confusion.
Describe the size and shape of the external auditory canal
- Irregular curved tube
- 25mm long
- Ovoid where its greatest diameter is vertically (8-9mm in adults)
- Narrowest point of the EAC is the isthmus
The EAC is tilt ____ and moves ______ to ____.
Upwards, Laterally to medially
List the landmarks of the EAC
- EAC
- TM
- Bone
- Cartilage
What is the function of the EAC?
Funnel sound to the TM and protects the middle & inner ear
What part of the EAC is fixed in diameter?
The bony portion
What part of the Eac is flexible?
The cartilaginous portion
When does the size and shape of the cartilaginous portion of the EAC changes?
With movement of the pinna & mandible
Where is the TM located?
The medial end of the EAC
How is the TM positioned and why is it positioned that way?
At angle to increase surface area for vibrations
Describe the size and shape of the TM.
- Cone-shaped
- Center pulled inward by 2mm
The shape of the TM aids in?
Producing a catenary level that amplifies sound vibrations
List the landmarks of the TM
- Annulus
- Short process of the malleus
- Pars flaccida
- Posterior fold
- Junction of incus and stapes
- Pars tensa
- Light reflex
- Umbo
- Handle of the malleus
- Anterior fold
What is the Isthmus?
The narrowest bend of the EAC where the cartilaginous portion of the canal meets the bony portion.
What is the annulus
- Thich fibrocartilaginous rim of the TM
- Has an horseshoe shape with an opening at the superior end near the pars flaccida
- Connected to a groove in the bony wall of the canal
What is the function of the Annulus?
Hold the TM in place
What is the pars flaccida?
- Small superior section
- Tissue of the TM that contains few internal fibers
- Loose
What does the pars tensa contain?
- Contains rest of the TM
- Contains internal fibers that hold tension over the TM
What are the tissues of the TM?
1, Outer Layer
- Middle Layer
- Inner Layer
The outer layer of the TM contains?
Epidermal epithelium
Which layer is continuous with the EAC?
Outer layer (Epidermal Epithelium)
The middle layer of the TM contains?
Collagen fibers that makes the TM springy
The inner layer of the TM contains?
Muscosal epithelium that is continuous with middle ear lining
List the collagen fibers of the TM
Radical & Concentric fibers
What causes cerumen to be produced in our EAC
The cartilaginous portion of EAC containing hair follicles, and the secretions of the ceruminous and aprocrine glands mixed with dead skin cells and other debris of the canal, produces cerumen
What part of the EAC can cerumen be found?
Lateral portion of the EAC
What are the glands that produce cerumen?
Ceruminous & Apocrine Glands
Explain how the mass and stiffness of an object affect its resonant frequency
Objects with heavier mass will produce lower pitches, while objects that are stiffer produce higher pitchers.