10-26
Receptors are exteroceptors because respond to chemicals in external environment
Interoceptors respond to chemicals in internal environment
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Detects sweet, sour, salty, bitter, & amino acids (umami)
Taste receptor cells are modified epithelial cells◦ 50-100 are in each
taste bud Each bud can
respond to all categories of tastants
Fig 10.7
10-28
Salty & sour do not have receptors; act by passing through channels
Fig 10.8
10-29
Sweet & bitter have receptors; act thru G-proteins
Fig10.8
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Olfactory apparatus consists of receptor cells, supporting cells, & basal cells ◦ Receptor cells are
bipolar neurons that send axons to olfactory bulb
◦ Basal cells are stem cells that produce new receptor cells every 1-2 months
◦ Supporting cells contain detoxifying enzymes
Fig 10.9
10-32
Odor molecules bind to receptors & act through G-proteins
Olfactory receptor gene family is huge
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10-34
Sound waves funneled by pinna (auricle) into external auditory meatus
External auditory meatus channels sound waves to tympanic membrane
Fig 10.1710-47
Malleus (hammer) is attached to tympanic membrane◦ Carries vibrations to incus (anvil)◦ Stapes (stirrup) receives vibrations from incus, transmits to
oval window
Fig 10.18
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Stapedius muscle, attached to stapes, provides protection from loud noises ◦ Can contract & dampen large vibrations◦ Prevents nerve damage in cochlea
10-50
Fig 10.18
Consists of a tube wound 3 turns & tapered so looks like snail shell
Fig 10.19
10-51
Tube is divided into 3 fluid-filled chambers◦ Scala
vestibuli, cochlear duct, scala tympani
Fig 10.19
10-52
Oval window attached to scala vestibuli (at base of cochlea)
Vibrations at oval window induce pressure waves in perilymph fluid of scala vestibuli
Scalas vestibuli & tympani are continuous at apex◦ So waves in vestibuli pass to tympani & displace
round window (at base of cochlea) Necessary because fluids are incompressible & waves would
not be possible without round window
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Low frequencies can travel all way thru vestibuli & back in tympani
As frequencies increase they travel less before passing directly thru vestibular & basilar membranes to tympani
Fig 10.20
10-54
High frequencies produce maximum stimulation of Spiral Organ closer to base of cochlea & lower frequencies stimulate closer to apex
Fig 10.2010-55
Is where sound is transduced
Sensory hair cells located on the basilar membrane ◦ 1 row of inner cells
extend length of basilar membrane
◦ Multiple rows of outer hair cells are embedded in tectorial membrane
Fig 10.22
10-56
Pressure waves moving thru cochlear duct create shearing forces between basilar & tectorial membranes, moving & bending stereocilia◦ Causing ion channels to open, depolarizing hair cells◦ The greater the displacement, the greater the amount
of NT released & APs produced
10-57
Info from 8th nerve goes to medulla, then to inferior colliculus, then to thalamus, & on to auditory cortex
Fig 10.23
10-58
Neurons in different regions of cochlea stimulate neurons in corresponding areas of auditory cortex◦ Each area of
cortex represents different part of cochlea & thus a different pitch
Fig 10.24
10-59
Conduction deafness occurs when transmission of sound waves to oval window is impaired◦ Impacts all frequencies◦ Helped by hearing aids
Sensorineural (perceptive) deafness is impaired transmission of nerve impulses◦ Often impacts some pitches more than others◦ Helped by cochlear implants
Which stimulate fibers of 8th in response to sounds
10-60
Provides sense of equilibrium◦ =orientation to
gravity Vestibular
apparatus & cochlea form inner ear
V. apparatus consists of otolith organs (utricle & saccule) & semicircular canals
Fig 10.11 10-35
Provide information about rotational acceleration
Project in 3 different planes
Each contains a semicircular duct
At base is crista ampullaris where sensory hair cells are located
Fig 10.12
10-42
Utricle and saccule provide info about linear acceleration
Semicircular canals, oriented in 3 planes, give sense of angular acceleration
Fig 10.12
10-37
Hair cells are receptors for equilibrium◦ Each contains 20-50 hair-like extensions called
stereocilia 1 of these is a kinocilium Fig 10.13
10-38
When stereocilia are bent toward kinocilium, hair cell depolarizes & releases NT that stimulates 8th nerve
When bent away from kinocilium, hair cell hyperpolarizes◦ In this way, frequency of APs in hair cells carries information
about movement Fig 10.13
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Have a macula containing hair cells◦ Hair cells embedded in gelatinous otolithic membrane
Which contains calcium carbonate crystals (=otoliths) that resist change in movement
Fig 10.14
10-40
Utricle sensitive to horizontal acceleration◦ Hairs pushed
backward during forward acceleration
Saccule sensitive to vertical acceleration
Hairs pushed upward when person descends
Fig 10.14
10-41
Provide information about rotational acceleration
Project in 3 different planes
Each contains a semicircular duct
At base is crista ampullaris where sensory hair cells are located
Fig 10.12
10-42
Hair cell processes are embedded in cupula of crista ampullaris
When endolymph moves cupula moves◦ Sensory processes
bend in opposite direction of angular acceleration
Fig 10.15
10-43
Fig 10.16
10-44
Vestibular nystagmus is involuntary oscillations of eyes that occurs when spinning person stops ◦ Eyes continue to move in direction opposite to spin,
then jerk rapidly back to midline Vertigo is loss of equilibrium
◦ Natural response of vestibular apparatus◦ Pathologically, may be caused by anything that alters
firing rate of 8th nerve Often caused by viral infection
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