Special Senses: Hearing Flashcards
Mechanoreceptor
sensory receptor that responds to mechanical pressure or distortion
Proprioceptors
Mechanosensory neurons that are important for balance
Sounds frequency range in Humans
50-18,000 cycles/sec
Sounds frequency range in Dogs
20,000 cycles/sec
Sounds frequency range in Bats
100,000 cycles/sec
Outer Ear Parts
Auricle/Pinna
Auditory Canal
Tympanic Membrane
Auricle/Pinna
Directs sound waves into the ear, can help in localization of sounds
Auditory Canal
aka. external acoustic meatus, pathway from the outer ear to the inner ear, made from cartilage and bone
Tympanic Membrane (eardrum)
splits outer and middle ear, sound wave transducer, long term is converting and amplifying vibration in the air to vibration in cochlear fluid
Middle Ear Parts
Malleus
Incus
Stapes
Tensor Tympani Muscle
Stapedius Muscle
Eustachian Tubes
Oval Window (Stapes)
Round Window
Malleus
ossicle, transmits and amplifies sounds from the tympanic membrane to the inner ear, hammer bone
Incus
ossicle, transmits and amplifies sounds from the tympanic membrane to the inner ear, anvil bone
Stapes
ossicle, transmits and amplifies sound vibrations from the incus to the oval window, stirrup bone
Tensor Tympani Muscle
pulls malleus away from the tympanic membrane, dampening expected loud sounds(chewing, shouting, thunder), will not work for sounds like gunshots or explosions
Stapedius Muscle
Pulls stapes away from the oval window, similar function to Tensor Tympani Muscle
Eustachian Tubes
links middle ear to nasopharynx, pressure equalization(swallowing and positive pressure open the tube) and mucus drainage,
Oval Window
membrane covered opening from the middle ear to the cochlea, connected to the stapes, by this point vibrations have been lowered in amplitude and increased in force
Round window
allows for the movement of fluid within the cochlea, allows for the fluid to vibrate, sound wave dissipates
Inner Ear Parts
Osseous Labyrinth:
Cochlea
Semicircular Ducts
Vestibule
Membranous Labyrinth:
Cochlear Ducts
Osseous Labyrinth
bony canals filled with perilymph,
3 parts: Cochlea, Semicircular Canals, Vestibule
contains membrane tubes and chambers(membranous labyrinth)
Cochlea
filled with watery fluid called endolymph, when the fluid moves the hair cells will detect movement and produce electrical signals which release neurotransmitters
Scala Vestibuli (vestibular duct)
perilymph filled cavity inside the cochlea
Reissner’s Membrane (vestibular membrane)
membrane inside the cochlea that separates the cochlear ducts from the vestibular ducts, helps transmit vibrations in the two ducts
Scala Tympani (tympanic duct)
perilymph filled cavity inside the cochlea
Basilar Membrane
stiff structural element of the cochlea, separates fluids of endolymph and perilymph from the Scala Tympani, vibrated according to tonal quantities of sound
Function of Reissner’s and Scala Tympani membrane
deform with soundwaves
sound waves the basilar membrane interacts with
narrow, thick basilar membrane, high tension + high frequency sound waves transduced here
helicotrema
wide, thin basilar membrane, low tension + low frequency sound waves transduced here
Semicircular canals
perilymph, contains semicircular ducts
vestibule
perilymph, contains utricle and saccule
Membranous Labyrinth
endolymph, from stria vascularis, high K+ content, made of the Cochlear Duct, Semicircular Ducts, and the Utricle/Saccule
Cochlear Duct (inside Cochlea)
contains hundreds of Organs of Corti, Tectorial membrane, Hair Cells ~20,000
Organ of Corti
located in Cochlear Duct, converts sounds into electrical signals, contains hair cells, send neurotransmitter signals to the brain
Hair Cell Arrangements
2.1 inner: (3500) 90% of sound innervation, sound transduction
2. 3 outer: (16500) 10% of sound innervation, alters characteristics of the basilar membrane
Sound Wave steps
deformation of membranes
hair cell is bent in one direction
hyperpolarization (other direction)
depolarization
apex of hair cell exposed to endolymph
base of hair cell exposed to perilymph
K+ moves from duct into hair cell
depolarization
Ca++ moves in
neurotransmitter release
stimulates Cochlear portion of Auditory nerve (8)
Semicircular Ducts
3 separate planes, inside the semicircular canals, filled with endolymph and hair cells, sensory for rotational movement
Cristae Ampullaris
sensory for angular acceleration and deceleration
Dynamic Equilibrium
angular acceleration, sense of rotational motion in the body
direction of fluid movement in the head
the opposite direction of the head movement due to inertia,
one side becomes hyperpolarized, the other becomes depolarized
Utricle/Saccule
contains Macula (hair cells) with Otoliths
gravity or acceleration cause depolarization
static equilibrium,
Motion Sickness
utricle/saccule vs conflicting visual signals
Conduction Deafness
problems with conducting sound vibrations (fused ear bones, ruptured ear drums, ear wax)
Nerve Deafness
damage to hair cells or cochlear nerves
Nystagmus Reflex
Rotate body
eyes slowly move in opposite direction of rotation,
can be horizontal or vertical,
eyes quickly jump back to centered position
Caloric Stimulation
insertion of water into the ear canal
convection moves endolymph
Nystagmus Reflex generated
Steps of Hearing
- Sound wave collected via auditory tube, vibrates tympanic membrane
- Amplified via ear ossicles
- Translated to cochlea via stapes on oval window
- Vibrates basilar membrane or helicotremma according to tonal qualities of sound
- Hair Cells and Organs of Corti are bent
- Depolarization due to an influx of K+ ions
- Sends neurotransmitter signals to brain
- Sound wave dissapates via round window
christae ampullaris function
measures angular acceleration
Vestibular apparatus contains the…
utricle + saccule, semicircular ducts
Vestibular apparatus senses…
- static equillibrium
- acceleration
- angular acceleration
