exam 4: CN VIII (36) Flashcards
The ear allows for the transformation of sound pressure waves into
electrical energy
The external ear captures sound (longitudinal) waves and transmits this energy to the middle ear via the ___________
tympanic membrane
The_____________ of the middle ear convert these pressure waves into mechanical energy.
ossicles (small bones)
Vibrations at the oval window by the stapes produces pressure waves within the _____________
perilymph (fluid) of the inner ear.
Movement of the perilymph displaces the membranes (tectorial, basement) affiliated with the cochlear duct, activating _______________
mechanically-gated ion channels of receptor (hair) cells.
___________ release neurotransmitter onto dendrites of cochlear neurons, transducing
the stimulus into an electrical impulse within cochlear neurons.
Hair cells
Movements of the head in various orientations activates ____________
mechanically-gated ion channels of receptor (hair) cells
Release of neurotransmitter by hair cells stimulates firing of electrical impulses by
vestibular neurons
Rotational movements of the head results in movement of fluids (perilymph, endolymph) within ______________stimulating hair cells affiliated with specialized organs _________
semicircular canals and ducts
crista ampullaris within the ducts
Translational movements of the head are detected by specialized organs _____________ that contain _______________________
macula utriculi, macula sacculi) that contain otoliths (ear stones)
External (outer) ear parts
▪ Pinna (a.k.a., auricle)
▪ Ear canal
Main divisions of the ear
1) External (outer) ear
2) Middle ear
3) Inner ear
what are the parts of the ear canal
▪ Vertical part
▪ Horizontal part– External acoustic meatus
Middle ear is housed in _____________
tympanic part of temporal bone
Parts of the Middle ear (3)
▪ Tympanic membrane (ear drum)
▪ Tympanic bulla (tympanic cavity)
▪ Auditory ossicles with associated muscles and
ligaments
Middle ear communicates with the _____________
nasopharynx via the auditory
tube
Inner ear housed in what part of the skull
petrous part of temporal bone
parts of the Inner ear
▪ Osseous labyrinth
▪ Membranous labyrinth
Auditory tube opens rostrally into the
nasopharynx = pharyngeal opening of the auditory tube
importance of the Auditory tube
Equalization of pressure; drainage of middle ear fluids
importance of the Tympanic bulla
▪ Hypo-expansion of middle ear cavity
▪ Divided in the cat
Bony promontory is a ventral expansion of the
petrous temporal bone
Tympanic plexus lies over its surface
Bony promontory
Ossicles (3 parts)
malleus, incus, stapes
middle ear components
▪ Auditory tube
▪ Tympanic bulla
▪ Bony promontory
▪ Ossicles (malleus, incus, stapes)
Passageway of communication between nasopharynx (external environment) and middle ear cavity.
auditory tube
primary function of auditory tube
equalize air pressure between middle ear and atmosphere
T/F auditory tube is normally open
false; Normally closed, opens when muscles connected to it contract
▪ Major contributor: tensor veli palatini muscle
auditory tube is important for drainage of
Drainage outlet for middle ear fluids
Clinical Connections of auditory tube:
Obstructions of auditory tube causes _________
increased pressure in middle ear cavity. Painful!
Clinical Connections of auditory tube:
Middle ear infections (otitis media) can cause swelling and blockage of _________
blockage of auditory tube with resultant effusion
Auditory tube:
T/F Polyps (middle ear, nasopharyngeal) are more likely to develop in cats
true
can there be obstruction of auditory tube.
YES
The tympanic bulla is divided into 2 compartments in the cat:
list them
▪ Ventromedial (larger compartment)
▪ Dorsolateral (smaller compartment)
identify the white and clear arrow
T/F bony promontory is affiliated with lots of nerves
true
Aggressive surgical curettage, middle ear polyps, and middle ear effusion can affect the nerves coursing through the _________
middle ear
Horner syndrome
what axons are associated
Sympathetic post-ganglionic axons
Chorda tympani nerve of CN VII:
hypogeusia/ageusia =
decreased/loss of taste
Tympanic plexus of CN IX:
hypogeusia/ageusia; decreased production of ______________
saliva via parotid salivary gland
the “handle” of the “hammer” is
embedded in the tympanic membrane
what is the handle and hammer referring to
The manubrium (“handle”) of the malleus (“hammer”)
Vibrations of the tympanic membrane, due to sound pressure waves, move the __________
malleus
The tympanic membrane has inner and
outer laminae and the__________ is
embedded between these.
manubrium
Middle ear ossicles:
Contraction of the_________________
dampens the movement of the malleus.
tensor tympani muscle
what is muscle is being pointed to
tensor tympani muscle
identify
the tympanic bulla
what kind of joints connect the middle ear
ossicles
Diarthrotic (synovial) joints
Movement of the malleus will, in turn, result in the movement of the ___ and ___
incus and stapes
Contraction of the _________ dampens the movement of the stapes at the oval window
stapedial muscle
▪ Arthritis – __________ hearing impairment
conductive
weakened or loss of middle ear reflexes
Myasthenia gravis
Caverns and tunnels within petrous temporal bone.
Osseous Labyrinth
Osseous Labyrinth and Membranous Labyrinth make up the _______
inner ear
Epithelial membrane sac within the osseous labyrinth.
Membranous Labyrinth
Regions of the osseous labyrinth include( 3)
▪ Vestibule (with vestibular, or oval, window)
▪ Cochlea (with cochlear, or round, window)
▪ Semicircular canals with ampullae
osseous labryinth contain (perilymph/endolymph)
▪ Contains perilymph
perilymph is similar to what kind of fluid
▪ Similar to CSF and extracellular fluid
▪ Low in K+ (~7 mM); high in Na+ (~140 mM)
The receptor organs of the inner ear are
components of the______________
membranous labyrinth
what is the Organ of hearing
Cochlear duct
what are the vestibular organs
▪ Ampullae of semicircular ducts
▪ Utriculus
▪ Saccule
membranous labyrinth contains (endolymph/ perilymph)
endolymph
endolymph is similar to what fluid
▪ Similar to intracellular fluid
▪ High in K+ (~150 mM); low in Na+ (~1 mM
Excavated space within the petrous temporal
bone
osseous cochlea
_____________ is centrally located within the space(osseous cochlea)
The bony modiolus (shaped kind of like a
screw)
The organ of hearing (a.k.a., organ of Corti) is a component of the ______________
membranous labyrinth.
Membranous cochlea:
▪ Extends from the “shelves” of the _____________
modiolus
Membranous cochlea:
▪ Contains specialized sensory cells (hair cells) that are ____________ activated
mechanically (mechanoreceptors)
Membranous cochlea:
mechanoreceptors release neurotransmitter onto what kind of neurons
bipolar (SSA) neurons
hair transduction:
Cell bodies of cochlear SSA neurons
are grouped within_____________
spiral ganglia
spiral ganglia (sensory/motor)
sensory
Axons from the spiral ganglia pass
through the ___________and extend to the ____________where they synapse in cochlear nuclei.
internal acoustic meatus and extend to the brainstem (myelencephalon)
identify
spiral ganglia
Vestibular transduction:
Hair cells are located in specialized organs of the semicircular ducts (cristae ampullares) and ___________________________
vestibule
(macula utriculi, macula sacculi)
Vestibular transduction:
Afferent neurons from these sensory organs form the vestibular portion of CN _____
CN VIII
Vestibular transduction:
Cell bodies of these vestibular SSA neurons are located in the _____________
Vestibular ganglia
Vestibular transduction:
Axons from the vestibular ganglia pass through the internal acoustic meatus and synapse in the vestibular nuclei of the ________
medulla oblongata (myelencephalon)
comprised of sensory neuron fibers from
vestibular organs (maculae; cristae ampullares); neuron cell bodies are in vestibular ganglia
Vestibular n.
comprised of sensory fibers from the organ of Corti; neuron cell bodies are in spiral ganglia
Cochlear n.
Vestibulocochlear nerve (CN VIII) leaves the petrous temporal bone via the ____________
internal acoustic meatus
sensory innervation of the ear (4)
▪ Cochlear n. of CN VIII
▪ Vestibular n. of CN VIII
▪ Facial n.
▪ Mandibular nerve of CN V
Cochlear n. of CN VIII function
▪ Hearing (SSA)
Vestibular n. of CN VIII function
▪ Balance (SSA)
Facial n. function for the ear
Concave aspect of pinna; large portion
of ear canal (GSA)
Mandibular nerve of CN V functions
Base of ear; small portion of ear canal
(GSA
Motor Innervation of the ear
▪ Facial n. (GSE to auricular mm.)
what would lesions of CN VII look like (6)
▪ Hearing loss
▪ Disorientation
▪ Nausea, loss of appetite
▪ Vestibular ataxia
▪ Head tilt, head turn, circling and/or leaning
towards the side of the lesion
▪ Resting nystagmus (involuntary eye movements); horizontal fast phase away from the side of the lesion
The external ear is supported by
the ___________ cartilage
auricular
what is the proximal and distal end of the auricular cartilage
▪ Proximal end of this cartilage =
vertical and horizontal ear canals
▪ Distal end of this cartilage = pinna
The shape of the pinna is dependent upon
composition of the fibroelastic auricular cartilage
T/F The collagen/elastin composition varies among species and breeds
true
The size and shape of the pinna determines which ____________ optimally and may also
help with ___________
sound frequencies are collected
noise reduction
what kind of ear is this
Non-erect
(Lop-eared)
what kind of ear is this
Erect
(V-shaped)
what kind of ear is this
Semi-erect
(Cocked)
the auricle( convex and concave) is covered by __________ which extends into the ear canal
hairy skin with glands (modified sweat glands) that produce cerumen is found within the ear canal
most common tumor of ear is known as
Ceruminous gland adenomas
Dermatologic disease can lead to ______ in the ear canal
otitis externa
the visible portion of the external ear has several regions that provide important surgical landmarks
list some
▪ Helix
▪ Scapha
▪ Anthelix
▪ Tragus
▪ Antitragus
▪ Tragohelicine incisure
▪ Intertragic incisure
▪ Cutaneous marginal pouch
from top to bottom
apex
Cutaneous marginal pouch
in addition to the auricular cartilage, what are the other 2 cartilages affiliated with the ear
annular and scutiform cartilage
the annular cartilage connects the cartilaginous meatus of the horizontal canal with the
bony external acoustic meatus
the _____________ serves as an attachment site for auricular muscle
scutiform cartilage
scutiform cartilage: what is its shape
A flat, boot-shaped cartilage
scutiform cartilage:
where is it located
Located medial and rostral to the base of
the auricle
scutiform cartilage:
what does it aid in
Aids in the redirection of the pull of some
of the auricular muscles.
the extensive movement of the auricle is permitted by the attachment of a ____________
complex group of auricular muscles
▪ Rostral Auricular Group
▪ Caudal Auricular Group
Motor innervation to the external ear is by CN ___
sensory innervation is by CN __,__,__
Motor: CN VII
Sensory: CN V, VII, II
what nerve is motor to external ear
Motor (CN VII)
▪ Auriculopalpebral n.
▪ Rostral auricular n.
▪ Caudal auricular n
what nerves are sensory to the external ear
Sensory (CN VII):
▪ Internal auricular n. (middle, caudal,
lateral brr.)
Sensory (CN V):
▪ Auriculotemporal n.
▪ Rostral auricular br. (there is a minimal
contribution of fibers from the vagus n. to
this branch)
zones of cutaneous innervation of the ear
nerves of the cervical plexus also supply ___________innervation to the external ear
cutaneous (sensory) innervation
▪ Great auricular n.
Ventral branch of C2
▪ Greater (a.k.a., major) occipital n.
Dorsal branch of C2
The second cervical nerve (C2) supplies
sensory innervation to the ________ surface of the external ear
convex
whereas the facial nerve supplies sensory innervation to the_______surface of
the external ear.
concave
auricular sensory zones of CN II
Great auricular n.
Ventral branch of C2
Greater (a.k.a., major) occipital n.
Dorsal branch of C2
