Canine CN VIII Flashcards
The ear allows for the transofrmation of sound pressure waves into what?
electrical energy
The external ear captures longitudinal sound waves and transmits this energy to the middle ear via?
the tympanic membrane
The ossicles (small bones) of the middle ear convert pressure waves into?
mechanical energy
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 affiliated with the cochlear duct, which activates what?
mechanically gated ion channels of receptor hair cells
Hair cells release neurotransmitter onto dendrites of cochlear neurons, transducing the stimulus into what?
an electrical impulse within cochlear neurons
Movements of the head in various orientations activates what?
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 within semicircular canals and ducts, stimulating what?
hair cells affiliated with specialized organs within the ducts
Translational movements of the head are detected by specalized organs that contain what?
otoliths
What are the specialized organs of the ear that detect translational movements?
- macula utriculi
- macula sacculi
What are the specialized organs of the ear within the ducts that are affiliated with hair cells?
crista ampullaris
The external ear includes what structures?
- pinna (auricle)
- ear canal (vertical and horizontal)
Where is the external acoustic meatus found?
horizontal part of ear canal
The middle ear includes what structures?
- tympanic membrane
- tympanic bulla
- auditory ossicles with associated muscles and ligaments
Where is the middle ear housed?
in tympanic part of temporal bone
The midde ear communicates with the nasopharynx via?
the auditory tube
The inner ear includes what structures?
- osseous labyrinth
- membranous labyrinth
The inner ear is housed where?
in petrous part of temporal bone
What middle ear component is divided in the cat?
tympanic bulla
The auditory tube is important for what?
- equalization of pressure
- drainage of middle ear fluids
What lies over the surface of the bony promontory of the middle ear?
tympanic plexus
The auditory tube opens rostrally into the nasopharynx. This opening is called what?
pharyngeal opening of the auitory tube
What are the three types of ossicles found in the middle ear?
- malleus
- incus
- stapes
What is the primary function of the auditory tube?
equalize air pressure between middle ear and atmosphere
What muscle is the major contributor to opening the auditory tube?
tensor veli palantini muscle
What is the passageway of communication between nasopharynx and middle ear cavity?
auditory tube
The tympanic bulla is divided into what two compartments in the cat?
- ventromedial (larger compartment)
- dorsolateral (smaller compartment)
What component of the middle ear is affiliated with lots of nerves?
bony promontory
The manubrium of the malleus is embedded where?
in the tympanic membrane
Vibrations of the tympanic membrane, due to sound pressure waves, do what?
move the malleus
Contraction of what muscle dampens the movement of the malleus?
tensor tympani muscle
What joints connect the middle ear ossicles?
diarthrotic (synovial) joints
Movement of the malleus will, in turn, result in the movement of what?
the incus and stapes
Contraction of what muscle dampens the movement of the stapes at the oval window?
stapedial muscle
What are the regions of the osseous labyrinth?
- vestibule (with vestibular, or oval, window)
- cochlea (with cochlear, or round, window)
- semicircular canals with ampullae
Perilymph of the osseous labyrinth is similar to what?
CSF and extracellular fluid
What structure refers to the caverns and tunnels within petrous temporal bone of the inner ear?
osseous labyrinth
The receptor organs of the inner ear are components of what?
the membranous labyrinth
What is the organ of hearing?
cochlear duct
What are the vestibular organs?
- ampullae of semicircular ducts
- utriculus
- saccule
The membranous labyrinth contains endolymph, which is similar to what?
intraceullar fluid
What is the excavated space within the patrous temporal bone?
osseous cochlea
What structure is centrally located within the osseous cochlea?
bony modiolus
Cell bodies of cochlear special somatic afferent (SSA) neurons are grouped within what?
spiral ganglia
Axona from the spiral ganglia pass through the internal acoustic meatus and extend to the brainstem where they synapse where?
in cochlear nuclei
What nerve is comprosed of sensory nuron fibers from vestibular organs and whose neuron cell bodies are in vestibular ganglia?
vestibular nerve
What nerve is comprised of sensory fibers from the prgan of corti and whose neuron cell bodies are in spiral ganglia?
cochlear nerve
What nerve leaves the petrous tempiral bone via the internal acoustic meatus?
vestibulocochlear nerve CN VIII
What nerves provide sensory innervation of the ear?
- cochlear nerve
- vestibular nerve
- facial nerve
- mandibular nerve
What nerve provides motor innervation of the ear?
- facial nerve
What would a lesion of CN VIII look like?
- 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; horizontal fast phase away from the side of the lesion
The external ear is supprted by what?
auricular cartilage
The shape of the pinna is dependent upon the composition of what?
the fibroelastic auricular cartilage
What determines which sound frequencies are collected optimally and may also help with noise reduction?
size and shape of the pinna
Modified hairy skin with glands that produce what are found within the ear canal?
cerumen
What cartilage serves as an attachment site for auricular muscles?
scutiform cartilage
Scutiform cartilage is located where?
medial and rostral to the base of the auricle
What nerves provide motor innervation to the external ear?
CN VII
- auriculopalpebral nerve (rostral auricular nerve)
- caudal auricular nerve
What nerves provide sensory innervation to the external ear?
CN VII
- internal auricular nerve
CN V
- auriculotemporal nerve (rostral auricular branch)
What nerves of the cervical plexus also supply cutaneous (sensory) innervation to the external ear?
- great auricular nerve
- greater occipital nerve
The second cervical nerve (C2) supplies sensory innervation to the _____ surface of the external ear; whereas the facial nerve supplies sensory innervation to the ____ surface of the external ear.
convex, concave
