Lecture 79 Flashcards
Hearing and equilibrium is borth transduced in inner ear. ___________ CN?
vestibulocochlear nerve (CN VIII)
passageways in petrous temporal bone
Bony labyrinth
connective tissue tubes within bony labyrinth
Membranous labyrinth
Membranous labyrinth: Filled with endolymph (blue fluid): similar to intracellular fluid, ___________ in K+
HIGH
Membranous labyrinth: Floating in perilymph (green fluid): similar to cerebrospinal fluid ___________ in K+
LOW
___________ is high in K+
endolymph
___________ is low on K+
Perilymph
organ of hearing
Cochlea
dorsal chamber
Scala vestibuli
Scala vestibuli is filled with ___________
perilymph
Scala vestibuli: Begins at ___________ and spirals to apex
Oval window
Ventral chamber
Scala tympani
scala tympani is filled with
perilymph
Scala tympani begins at apex and ends at ___________ (secondary tympanic membrane)
round window
___________ triangular middle chamber
Scala media
scala media is filled with
endolymph (K+ rich)
Stereocilia of hair cells of Organ of Corti are embedded in the ___________
tectorial membrane
Transducers of vibration “hair cells” on them (mechanoreceptors)
Organ of corti
Transduction: Inner hair cells contain ___________ at their tips and tip link proteins that connect them
ion channels
Transduction:
When the basilar membrane moves up,hair cells are pushed into ___________ and their tips are tilted,pulling tip links
tectorial membrane
Transduction: Tip links pull open ion channel allowing K+ to diffuse into the hair cell and ___________
depolarize it
Transduction: Hair cells releases neurotransmitter from their base, exciting the ___________
cochlear branch of CN VIII
conditions interfere with transmission of vibrations to inner ear
Conductive deafness
examples of conduction deafness
Damaged tympanic membrane, Otitis media, Tumors, polyps, Other causes of middle ear effusions (fluid)
death of hair cells, CNVIII, or any CNS system elements concerned with hearing
Sensorineural (nerve) deafness
Examples of sensorineural deafness
Genetic (congenital), Geriatric (age-related), Acquired (infections, trauma, loud noises, tumor)
Auditory pathway: Cochlear n. ___________ order neuron
1st order neuron
Auditory pathway: ___________ in medulla
Cochlear nuclei
Auditory pathway: ___________ (dorsal nucleus of the trapezoid body (superiorolivary nucleus) to the Decussate to the DNTB or lateral lemniscus)
2nd order neurons
Auditory pathway: Caudal colliculus
tectospinal tract
Auditory Pathway: Medial geniculate nucleus
primary auditory cortex (temporal lobe)
Olfaction and Gustation: Receptors are
chemoreceptors
Olfaction and Gustation: Transduce chemical signals into
electric signals
Olfaction and Gustation: ___________ cell is primary afferent neuron itself
Olfactory receptor cell
___________ is a specialized epithelial cell (‘sense organ’) thattransduces chemical signals and then sends electrical signals to aprimary afferent neuron
Gustatory receptor
During sniffing it brings odorants into
Olfactory areas (unidirectional laminar flow)
Olfactory receptors only lineolfactory epithelium on
ethmoturbinates
Rest of turbinate lining is made up of respiratory epithelium means ___________
No olfactory capability
Olfactory receptor cells
primaryafferent neuron (Bipolar)
Odorant molecules bind to receptors located on ___________ that protrude into the nasal cavity
cilia
Olfactory epithelium contains 3 cells which are
olfactory receptor cells, supporting cells and basal cells
Olfactory transduction: First, Odorant binds ___________ on olfactory receptor cell
GPCR
Olfactory transduction: Then the G-protein subunit activates ___________ which converts ATP to cAMP (acyclic nucleotide
adenylyl cyclase
Olfactory transduction: Third step, cAMP opens Ca, K, Na channels. There is an EFFLUX OF?
CL-
Olfactory transduction: CL- efflux causes membrane depolarization and the ___________
Action potential generated in olfactory neuron’s axon
1st order neuron throughcribiform plate to ___________
olfactory bulb
Olfactory bulb ___________ process, filter, and enhance transmission of specific odorants
interneurons
2nd order neuron = ___________ (Axons project to cerebrum)
Mitral cell
Olfactory pathway: ___________ path to olfactory cortex(piriform lobe)
Direct
Olfactory pathway: Transmission through thalamus is ___________
not required
Connected to the nasal and the oral cavity via the nasopalatine ducts (NPD); Pheromones are introduced to the NPD through inhalation in some species and through liquid/mucus in others; VNO fibers to accessory olfactory bulb and then on to the olfactory cortex
Vomeronasal organ
___________ is the sensory organ for taste?
Taste buds
___________ are found on the gustatory papillae of the tongue
Circumvallate (Vallate); Foliate; Fungiform
Taste buds are the ___________ for taste
sensory organs
Taste receptor cells have microvilli that contain the taste ___________
chemoreceptors
For bitter, sweet or savory tatse the receptor cell is
depolarized
For sour or salty taste the receptor cell is also depolarized because
Chemicals bind and directly openionotropic epithelial sodium channelsto allow H+ or Na+ to enter,respectively
for bitter, sweet and savory they bind to GPCRs and this increases IP3 and DAG and opens
TRP channels
sour and salty taste enters through membrane Na channels (___________)and cause depolarization
ENaC
Primary afferent axons of these first order taste neurons are in cranial nerves ___________
IX, VII, and X
Afferent axons enter the brainstem and reach second order neurons in the
solitary nucleusof the medulla
Second order neurons send axonal projections to ___________ in the thalamus
third order neurons
Third order neurons project to the ___________ of the temporal lobe
taste cortex
