Olfaction, Taste, Hearing & Equilibrium Flashcards
the auditory part of the labyrinth
cochlea
otolith organs and the semicircular canals
form the vestibular part of the labyrinth.
a perception of sound energy
Hearing
Hearing involves two aspects:
identification of the sounds (what?) and their localization (where?).
The specialized receptors for sound are located in the _______ inner ear.
fluid-filled
The inside of the tympanic membrane is exposed to the atmospheric pressure through the ______ ______, which connects middle ear to the pharynx.
Eustachian tube
________ opens the Eustachian tube and allows the pressure on the both sides of the tympanic membrane to equalize
Yawning
transfers the vibratory movements of the tympanic membrane to the fluid of the inner ear.
The middle ear
structures of the middle ear amplify the force of sound waves, resulting in _______ forces at the oval window
pressure
Cochlea is divided into three compartments
scala media (endolymph), scala vestibular and scala tympani (perilymph).
Basilar membrane bears the ______ of ______, the sense organ of hearing
organ of Corti
•Protruding from surface of each hair cell are about 100 hairs, known as
stereocilia
The stereocilia are mechanically embedded in the
tectorial membrane
has a high [K+]
Endolymph
displacement of stereo cilia toward the kinocilium open ________ cation channel.
K+ entry causes depolarization of hair cell membrane.
Leads to ____ entering, and _________ of neurotransmitter = depolization of auditory neuron
nonsleective
Ca
exocytosis
Afferent fibers from spiral ganglion form, which joins vestibular nerve to become the vestibulocochlear nerve (VIII)
the auditory (cochlear) nerve.
Sends information to other cortical processing areas: e.g. Wernicke’s area (understanding of written and spoken language)
Auditory cortex
processes of acoustic signals to
distinguish if they are speech, music, or noise.
Wernicke’s area
Occurs due to blockage of the ear canal with earwax, rupture of the tympanic membrane, middle ear infections with fluid accumulation, bony adhesions between the stapes and the oval window.
conductive deafness
The defect can lie in the organ of Corti or the auditory nerves or, rarely, in the ascending auditory pathways or auditory cortex.
sensorineural deafnessa
a degenerative, age-related process that occurs as hair cells “wear out” with use.
Neural presbycusis
Decreased number of hair cells, loss of spiral ganglion, formation of reactive oxygen species
Amynoglycoside antibiotics
Decreased number of hair cells, changes in mitochondrial function, direct cell death
Chemotherapeutic agents
Reduction in endocochlear potential
Chemotherapeutic agents, diuretics, and aminoglycosides
Disruption of endocochlear fluid homeostasis, disruption of endolymph homeostasis
Diuretics
Decreased cochlear blood flow due to inhibition of prostaglandin synthesis
Quinine and salicylates
Activation of NMDA receptors has been implicated in tinnitus induction
Quinine and salicylates
although used alone cause only temporary hearing loss, they potentiate the toxicity of other ototoxic agents
Diuretics
hearing loss is generally reversible and usually occurs only with high doses
Quinine and salicylates
these drugs can cause permanent hearing loss
Amynoglycoside antibiotics
may occur as a result of disorders in the middle or inner ear or along the central neuronal pathways.
Tinnitus
treament of tinnitus
ignore sounds
•Provides information essential for the sense of equilibrium and for coordinating head movements with eye and postural movements
Vestibular system
Vestibular system consists of two sets of structures
semicircular canals and the otolith organs
provide information about the position of the head relative to the gravity and detect changes in the rate of linear motionOtolith organs
Otolith organs
detect rotational and angular acceleration or deceleration of the head, such as when starting or stopping spinning, or turning the head.
The semicircular canals
Superior, horizontal and posterior canals hair cells are located in a swelling called the
ampulla.
The cilia of the hair cells project into a gelatinous mass called the _______.
Movements cause generation of receptor potentials in the hair cells
cupula
the sensation that either the body or the environment are moving, when actually both are stationary = spinning sensation
Vertigo
a sensation of lightheaded-
ness, faintness, or unsteadiness
Dizziness
the most common cause of pathologic vertigo
Vestibular dysfunction
Spatial orientation and posture are controlled by three sensory systems:
vestibular, visual and somatosensory; a mismatch between any of these can result in vertigo.
an abnormality of the inner ear causing vertigo or severe dizziness, tinnitus, fluctuating hearing loss, nystagmus, and the sensation of pressure or pain in the affected ear
Ménière disease
Ménière disease treatment
There is no cure, but the symptoms can be controlled by reducing the fluid retention through dietary changes (low-salt or salt-free diet, no caffeine, no alcohol) or with diuretics.
Nausea and vomiting are caused by stimulation of the
vomiting center in the medulla
Drugs used to prevent motion sickness suppress signals between vestibular nuclei and the vomiting center. They target
muscarinic and histaminic (H1) synaptic receptors
a belladonna alkaloid, which acts by blocking cholinergic transmission from the vestibular nuclei to higher centers in the CNS.
Scopolamine
primarily a H1-antagonist, but also has an antimuscarinic effect
•Dramamine (dimenhydrinate)
an antihistaminic agent (marketed as “Dramamine II”) less likely to cause drowsiness.
•Meclizine
•Axons of the olfactory sensory neurons enter ______ _____, where they synapse with second-order neurons
olfactory bulb
From olfactory bulb the information is transmitted to higher brain structures including the (3)
piriform cortex, hippocampus and amygdala
can result from nasal congestion, damage to the olfactory nerves, tumors (neuroblastomas, meningiomas), infections, overuse of nasal vasoconstrictors, smoking.
Anosmia and hyposmia
_________ disease can also damage the olfactory nerves
alzheimers
a homeopathic intranasal substance marketed to alleviate cold symptoms, has been implicated in olfactory dysfunction
Zicam
Taste receptors are located on projections from the surface of the tongue called
papillae
Each papillae has numerous ______, which open onto the surface of the tongue at a small depression called the _______
taste buds
taste pore
•Each taste bud contains approximately 100 taste receptor cells with
microvilli.
Sour taste is caused by
acids, which contain free H+.
______ substances use intracellular second messengers: binding of glucose » cAMP production» depolarization of the receptor cell membrane.
sweet
receptors use
more than one transduction mechanism depending on the tastant: direct binding to K+ channel and changes in second messengers.
bitterness
taste is elicited by activation of ionotropic glutamate receptor, which mediates depolarization.
Umami taste
