Special Senses - EAR Flashcards
which part of the ear conducts sound to the oval window
the middle ear
what part of the ear is responsible for collecting sound waves and focusing them inward
the external ear
which part of the ear contains the hearing and equilibrium receptors
internal ear
what is the name given to the shell-shaped projection surrounding the opening of the external auditory canal? It is composed of elastic cartilage covered with thin skin and an occasional hair.
Pinna (Auricle) - this is the ear
what is the name of the structure of the ear that is a short, curved tube that extends from the auricle to the eardrum
the auditory canal
what three structures make up the external ear
the pinna (auricle) external auditory canal tympanic membrane (eardrum)
what is the structure of the ear that is a thin, semitransparent partition between the external auditory canal and the middle ear
eardrum, or tympanic membrane
where is the middle ear located
in the temporal bone
what resides at the most outer (lateral) wall of the middle ear
the tympanic membrane (eardrum)
what does the most inner (medial) border of the middle ear consist of
a thin bony plate with two small openings: the oval and the round windows.
what are the three tiny bones found in the middle ear
Auditory Ossicles:
- maleus (the hammer)
- incus (the anvil)
- stapes (the stirrup)
*the “handle” of the “hammer” is connected to the tympanic membrane.
what are the two small skeletal muscles which are attached to the ossicles
- tensor tympani
- stapedius muscle
the tensor tympani is innervated by the _____ branch of which CN?
mandibular branch of CN V (trigeminal)
what is the function of the tensor tympani
it limits movement and increases tension on the eardrum to prevent damage to inner ear from loud noises
the stapedius muscle is innervated by which CN?
CN VII (facial)
what is the smallest muscle in the body
the stapedius muscle
what is the function of the stapedius muscle
by dampening large vibrations of the stapes due to loud noises, it protects the oval window, but also decreases sensitivity of hearing.
hyperacusia
hypersensitivity of hearing which occurs when there is paralysis of the stapedius muscle
how does the middle ear communicate wit the nasopharynx
via the auditory (pharyngotympanic) or Eustachian tube.
it is normally closed at the pharyngeal pole, however during yawning/swallowing, it becomes open to allow air to enter/exit the middle ear until pressure in the middle ear is equal with the atmospheric pressure.
describe the inner ear
aka labyrinth; canal/net-like structure; consists of bony outer labyrinth and membranous inner labyrinth.
the inner ear is divided upon three portions. what are they?
- semicircular canals
- vestibule
- cochlea
which parts of the inner ear contain receptors for equilibrium
semicircular canals and the vestibule
which part of the inner ear contains receptors for hearing
the cochlea
the bony labyrinth is lined with _____
periosteum
what is the fluid similar to CSF that flows between the bony and membranous labyrinth
perilymph
inside the membranous labyrinth, there is a flow of _____. what is this fluid’s importance?
endolymph; this fluid contains an unusually high level of potassium ions (K+), and potassium plays a role in the generation of auditory signals.
The membranous labyrinth in the vestibule contains two small structures: _____ and _____. They are filled with _____. Each contains sensory epithelium: _____ _____ and _____ _____.
utricle; saccule; endolymph; macula utriculi and macula sacculi.
projecting from the vestibule are three bony semicircular canals. they are called:
At one end of each canal is a swollen enlargement called:
anterior, posterior and lateral semicircular canal, based on their orientation
ampulla
the portions of the membranous labyrinth that lie inside the bony semicircular canals are called:
they communicate with:
semicircular ducts
the utricle of the vestibule
CN VIII (vestibulocochlear) has cochlear (auditory) and vestibular (equilibrium) portions. what nerves are found in the vestibular portion?
the axons in this portion consist of:
the cell bodies of the sensory neurons are located in the _____ _____
ampullary, utricular, and saccular nerves.
first order sensory neurons and axons of motor efferent neurons for equilibrium.
vestibular ganglia
the cochlea spirals around a central core called the:
modiolus
what are the three channels the cochlea is divided into
- scala vestibuli
- scala tympani
- cochlear duct/scala media
of the three channels of the cochlea, which enclose perilymph and which enclose endolymph
the scala vestibuli and the scala tympani enclose perilymph, and the cochlear duct encloses endolymph
what is the name of the opening at the apex of the cochlea?
which two cochlear channels communicate here?
helicotrema
scala vestibuli and scala tympani communicate here
the scala vestibuli is the opening to the _____
vestibule
the vestibular membrane separates the _____ _____ from the _____ _____
cochlear duct from the scala vestibuli
the _____ _____ separates the scala tympani from the cochlear duct
basilar membrane
the _____ _____ _____ _____ is resting on the basilar membrane and contains about 16,000 hair cells and supporting cells
spiral organ of corti
each hair cell has a tip of hair bundle (hair cilia) which are bathed in:
endolymph
where are cell bodies for the hearing sensory neurons located
in the spiral ganglion
the _____ membrane covers the hair cells like a roof. Movement of this membrane produces movement of the cilia, which in turn triggers:
tectorial membrane
depolarization of hair cells
describe the auditory pathway
first order sensory neurons (spiral ganglion —> cochlear branch of CN VIII) —>cochlear nuclei in the medulla oblongata (same side) and superior olivary nuclei in the pons (both sides) —> inferior colliculi in the midbrain (second order neurons) —> medial geniculate body of the thalamus (3rd order neurons) —> primary auditory cortical area in the superior temporal gyrus (41, 42) receive impulses from both sides.
describe the equilibrium pathway
sensory receptors (hair cells) of two maculae —> vestibular neuron bodies in vestibular ganglia (first order neurons) —> vestibular axons of CN VIII —> vestibular nuclei of the medulla and pons (second order neurons) —> cerebrum and cerebellum.
Also, axons from all vestibular nuclei extend motor fibers to CN III, VI, and XI to control movement of the eyes, head and neck.
In addition, axons from vestibulospinal tract control tone of the skeletal muscles in response to the head movement.
