Lecture 22 Auditory 1 Flashcards
Are each of the following parts of the ear air-filled or fluid-filled: external, middle, inner ear?
external (air) middle (air) inner (fluid filled)
What two nerves come together to form CN VIII?
vestibular and cochlear nerves (innervate hair cells
Which parts of the branchial arches come together to form the ear (external, middle and inner)
the first branchial cleft and the 1st branchial pouch between arch 1 and arch 2 (separated by the ear drum)
The bones of the ear are formed from which brachial arches?
cartilage from BA 1 forms the malleus and incus, cartilage from BA 2 forms the stapes
What developmental material forms the membranous labyrinth?
the otic placode (thickening of surface ectoderm) invaginates to form the otic pit which is later innervated by CN VIII
What nerves (off which branches) serve the sensory innervation of the outer ear?
auriculotemporal n. (branch of mandibular branch V3), greater auricular n. (branch of the cervical plexus), Arnolds/ Alderman’s nerve (branches of CN VII, CN X) (can contribute to coughing or gagging when ear is stimulated)
Sensory to the ear via VII and X use which nucleus in the brain?
trigminal chief and spinal nuclei of V
Describe the different sources of ear drum innervation (complicated).
outer surface (V3, VII and X) inner surface (IX)
What would you expect to see on the outside surface of the ear drum?
cone of light (in the down and front position), imprint of the incus
What is sound?
Sound is a mechanical disturbance propagated through an elastic medium (wave disturbance that transfers progressively in space
What are two ways that the period of a wave can be measured?
length of the period in time (Hz = cycles/sec) or space (wavelength=meters) BONUS: pure tone sounds are sinusoidal
Decibel system is calculated in a _____ scale and the calculation is made in relation to P2 which is a reference sound based on what?
logarithmic; P2 is a reference for 0 dB, it is generally considered the threshold of perceivable sound
Is hearing sensitivity the same over all frequencies? explain.
hearing sensitivity is not the same at all frequencies, it is best in the speech frequency range
What is the general range of Hz a human can generally detect?
20 Hz- 20,000 Hz— means sensing sounds 1,000,000x louder than the slightest tone perceivable
The external auditory meatus is contained with a cranial bone, which?
temporal bone
Describe the orientation of the tympanic membrane.
it faces down and in front of the ear
The middle ear is open to the outer would via which opening
the auditory/ eustachian tube opens into the nasopharynx
Name the three membranes of the middle ear.
tympanic membrane, oval window and round window
Describes the two muscle found in the middle ear.
tensor tympani (CNV) attaches to the malleus and to the anterior wall of the middle ear; and the stapedius (CN VII) attaches to the stapes and the posterior middle ear
What caries the sensory innervation to the middle ear?
tympanic branch of the petrosal nerve (CNIX) while salvation parasympathetics continue on BONUS: VII passes through in a canal behind the middle ear and exits through the stylomastoid foramen
What is the function(s) of the middle ear bones?
amplify and transfer the of sound from the air to the fluid of the inner ear (the area of the drum is 21 times greater than the area of the oval window
Describe the general structure the inner ear.
the bony ducts surround the membranous ducts inside includes the hair cells (the vestibular part, the membranous ducts are against the walls, while in the cochlear part of the membranous divide the bony ducts
What three ducts does the membrane divide the chochlea into?
Scala vestibuli, the scala media and the scala tympani
Describe the membranous borders of the scala media.
Reissner’s membrane and the basilar membrane (contains the hair cells) both connect to the bony lip of the labyrinth
