CHAPTER 15 THE SPECIAL SENSES

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THE SPECIAL SENSES Overview

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Which of these is NOT a special sense? 1) 2) 3) 4) 5)

touch sight taste smell hearing

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THE SPECIAL SENSES VISION

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Figure 15.1b The eye and associated accessory structures.

Levator palpebrae superioris muscle Orbicularis oculi muscle Eyebrow Tarsal plate Palpebral conjunctiva Tarsal glands Cornea Palpebral fissure

Eyelashes Bulbar conjunctiva Conjunctival sac

Orbicularis oculi muscle (b) Lateral view; some structures shown in sagittal section Copyright © 2010 Pearson Education, Inc.

Figure 15.2 The lacrimal apparatus.

Lacrimal sac Lacrimal gland Excretory ducts of lacrimal glands Lacrimal punctum Lacrimal canaliculus

Nasolacrimal duct Inferior meatus of nasal cavity Nostril

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Figure 15.3a Extrinsic eye muscles.

Superior oblique muscle Superior oblique tendon Superior rectus muscle Lateral rectus muscle

Inferior rectus Inferior oblique muscle muscle (a) Lateral view of the right eye Copyright © 2010 Pearson Education, Inc.

Figure 15.3b Extrinsic eye muscles.

Trochlea Superior oblique muscle Superior oblique tendon Superior rectus muscle

Axis at center of eye Inferior rectus muscle

Medial rectus muscle Lateral rectus muscle Common tendinous ring (b) Superior view of the right eye Copyright © 2010 Pearson Education, Inc.

Figure 15.4a Internal structure of the eye (sagittal section).

Ora serrata Ciliary body Ciliary zonule (suspensory ligament) Cornea Iris Pupil Anterior pole Anterior segment (contains aqueous humor) Lens Scleral venous sinus Posterior segment (contains vitreous humor) (a) Diagrammatic view. The vitreous humor is illustrated only in the bottom part of the eyeball. Copyright © 2010 Pearson Education, Inc.

Sclera Choroid Retina Macula lutea Fovea centralis Posterior pole Optic nerve

Central artery and vein of the retina Optic disc (blind spot)

Figure 15.4b Internal structure of the eye (sagittal section).

Ciliary body Ciliary processes Iris Margin of pupil Anterior segment Lens Cornea Ciliary zonule (suspensory ligament)

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Vitreous humor in posterior segment Retina Choroid Sclera Fovea centralis Optic disc Optic nerve

(b) Photograph of the human eye.

Which layer of the eye contains photoreceptors? 1) sclera 2) choroid 3) retina

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Quiz Q4: Which nerve controls the muscles that move the eyeball? 1) 2) 3) 4)

Vagus nerve Phrenic nerve Oculomotor nerve Sciatic nerve

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Quiz Q5: True or false: Tears are produced In the medial corner of the eye. 1) True 2) False

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Figure 15.5 Pupil dilation and constriction, anterior view.

Parasympathetic +

Sphincter pupillae muscle contraction decreases pupil size.

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Sympathetic +

Iris (two muscles) • Sphincter pupillae • Dilator pupillae

Dilator pupillae muscle contraction increases pupil size.

Figure 15.6a Microscopic anatomy of the retina.

Pathway of light

Neural layer of retina

Pigmented layer of retina Choroid Sclera

Optic disc

Central artery and vein of retina

Optic nerve

(a) Posterior aspect of the eyeball Copyright © 2010 Pearson Education, Inc.

Figure 15.6b Microscopic anatomy of the retina.

Ganglion cells

Bipolar cells

Amacrine cell

Photoreceptors • Rod • Cone

Horizontal cell Pathway of signal output Pigmented layer of retina Pathway of light (b) Cells of the neural layer of the retina Copyright © 2010 Pearson Education, Inc.

Figure 15.6c Microscopic anatomy of the retina.

Nuclei of ganglion cells

Outer segments of rods and cones

Nuclei Axons of Nuclei of of bipolar ganglion rods and cells cells cones (c) Photomicrograph of retina Copyright © 2010 Pearson Education, Inc.

Choroid

Pigmented layer of retina

A neuron which receives information from a rod or cone and passes it to another neuron is called a… 1) 2) 3) 4) 5)

Photoreceptor Retina cell Bipolar cell Ganglion cell Optic nerve cell

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Figure 15.7 Part of the posterior wall (fundus) of the right eye as seen with an ophthalmoscope.

Central artery and vein emerging from the optic disc

Macula lutea Optic disc Retina

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Figure 15.8 Circulation of aqueous humor.

Cornea

Lens

Iris Lens epithelium Lens

Cornea Corneal epithelium Corneal endothelium Aqueous humor Anterior Anterior segment chamber (contains Posterior aqueous chamber 3 humor) Scleral venous sinus 1 Aqueous humor is Cornealformed by filtration scleral junction

2

from the capillaries in the ciliary processes. Bulbar 2 Aqueous humor flows from the conjunctiva posterior chamber through the pupil Sclera into the anterior chamber. Some also flows through the vitreous humor (not shown). 3 Aqueous humor is reabsorbed into the venous blood by the scleral venous sinus. Copyright © 2010 Pearson Education, Inc.

Posterior segment (contains vitreous humor) Ciliary zonule (suspensory ligament) 1

Ciliary processes Ciliary muscle

Ciliary body

Figure 15.9 Photograph of a cataract.

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Figure 15.10 The electromagnetic spectrum and photoreceptor sensitivities.

Gamma rays

X rays

UV

Infrared

MicroRadio waves waves

(a)

Light absorption (pervent of maximum)

Visible light

(b) Copyright © 2010 Pearson Education, Inc.

Blue cones (420 nm)

Green Red cones cones Rods (500 nm) (530 nm) (560 nm)

Wavelength (nm)

Figure 15.11 Refraction.

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Figure 15.12 Bending of light by a convex lens.

Point sources

Focal points

(a) Focusing of two points of light.

(b) The image is inverted—upside down and reversed. Copyright © 2010 Pearson Education, Inc.

Figure 15.13a Focusing for distant and close vision.

Sympathetic activation

Nearly parallel rays from distant object Lens

Ciliary zonule Ciliary muscle

Inverted image

(a) Lens is flattened for distant vision. Sympathetic input relaxes the ciliary muscle, tightening the ciliary zonule, and flattening the lens. Copyright © 2010 Pearson Education, Inc.

Figure 15.13c Focusing for distant and close vision.

View Ciliary muscle Lens Ciliary zonule (suspensory ligament) (c) The ciliary muscle and ciliary zonule are arranged sphincterlike around the lens. (Anterior segment as viewed from within the eye.) Copyright © 2010 Pearson Education, Inc.

Figure 15.13b Focusing for distant and close vision.

Parasympathetic activation

Divergent rays from close object

Inverted image

(b) Lens bulges for close vision. Parasympathetic input contracts the ciliary muscle, loosening the ciliary zonule, allowing the lens to bulge. Copyright © 2010 Pearson Education, Inc.

Figure 15.14 Problems of refraction (1 of 3).

Emmetropic eye (normal) Focal plane

Focal point is on retina.

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Figure 15.14 Problems of refraction (2 of 3).

Myopic eye (nearsighted)

Eyeball too long

Uncorrected Focal point is in front of retina.

Corrected Copyright © 2010 Pearson Education, Inc.

Concave lens moves focal point further back.

Figure 15.14 Problems of refraction (3 of 3).

Hyperopic eye (farsighted)

Eyeball too short

Uncorrected Focal point is behind retina.

Corrected Copyright © 2010 Pearson Education, Inc.

Convex lens moves focal point forward.

An image of an object is presented ________ on the retina. 1) 2) 3) 4)

Upside down and mirror image Upside down and reversed Right side up and mirror image Right side up and reversed

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A myopic person cannot see distant images well because… 1) 2) 3) 4)

Their eyeball is too long Their eyeball is too short Their eyeball is too wide Their eyeball is too narrow

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Figure 15.15a Photoreceptors of the retina.

Process of bipolar cell Synaptic terminals

Rod cell body

Rod cell body

Cone cell body

Nuclei

Outer fiber

Mitochondria

(a) The outer segments of rods and cones are embedded in the pigmented layer of the retina. Copyright © 2010 Pearson Education, Inc.

Pigmented layer Outer segment

Inner segment

Inner fibers

Connecting cilia Apical microvillus

Melanin granules

Discs containing visual pigments Discs being phagocytized Pigment cell nucleus Basal lamina (border with choroid)

Figure 15.15b Photoreceptors of the retina.

Rod discs

Visual pigment consists of • Retinal • Opsin (b) Rhodopsin, the visual pigment in rods, is embedded in

the membrane that forms discs in the outer segment.

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Figure 15.16 The formation and breakdown of rhodopsin.

11-cis-retinal

1 Bleaching of

2H+

Oxidation Vitamin A

11-cis-retinal

Rhodopsin

Reduction 2H+

2 Regeneration

of the pigment: Enzymes slowly convert all-trans retinal to its 11-cis form in the pigmented epithelium; requires ATP.

Dark

Light

Opsin and All-trans-retinal

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the pigment: Light absorption by rhodopsin triggers a rapid series of steps in which retinal changes shape (11-cis to all-trans) and eventually releases from opsin.

All-trans-retinal

Figure 15.17 Events of phototransduction.

1

Light (photons) activates visual pigment. Visual pigment

Phosphodiesterase (PDE) All-trans-retinal

Light

Open cGMP-gated cation channel

11-cis-retinal Transducin (a G protein) 2

Visual pigment activates transducin (G protein).

3

Transducin activates phosphodiester ase (PDE).

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4

PDE converts cGMP into GMP, causing cGMP levels to fall.

5

Closed cGMP-gated cation channel

As cGMP levels fall, cGMP-gated cation channels close, resulting in hyperpolarization.

Figure 15.18 Signal transmission in the retina (1 of 2).

In the dark 1 cGMP-gated channels open, allowing cation influx; the photoreceptor depolarizes.

Na+ Ca2+

Photoreceptor cell (rod)

2 Voltage-gated Ca2+ channels open in synaptic terminals. 3 Neurotransmitter is released continuously.

Ca2+

4 Neurotransmitter causes IPSPs in bipolar cell; hyperpolarization results. 5 Hyperpolarization closes voltage-gated Ca2+ channels, inhibiting neurotransmitter release.

6 No EPSPs occur in ganglion cell. 7 No action potentials occur along the optic nerve. Copyright © 2010 Pearson Education, Inc.

Bipolar cell

Ganglion cell

Figure 15.18 Signal transmission in the retina (2 of 2).

In the light 1 cGMP-gated channels are closed, so cation influx stops; the photoreceptor hyperpolarizes.

Light

Photoreceptor cell (rod)

2 Voltage-gated Ca2+

channels close in synaptic terminals.

3 No neurotransmitter is released. 4 Lack of IPSPs in bipolar cell results in depolarization. 5 Depolarization opens voltage-gated Ca2+ channels; neurotransmitter is released.

Bipolar cell Ca2+

Ganglion cell Copyright © 2010 Pearson Education, Inc.

6 EPSPs occur in ganglion cell.

7 Action potentials propagate along the optic nerve.

The protein responsible for detecting light in rods is… 1) 2) 3) 4)

Vitamin A photoreceptor 11-cis-retinal rhodopsin

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True or False: Photoreceptors generate action potentials when they are stimulated by light. 1) True 2) False

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Figure 15.19a Visual pathway to the brain and visual fields, inferior view.

Fixation point

Right eye Suprachiasmatic nucleus Pretectal nucleus Lateral geniculate nucleus of thalamus Superior colliculus

Left eye Optic nerve Optic chiasma Optic tract

Uncrossed (ipsilateral) fiber Crossed (contralateral) fiber Optic radiation

Occipital lobe (primary visual cortex) (a) The visual fields of the two eyes overlap considerably. Note that fibers from the lateral portion of each retinal field do not cross at the optic chiasma. Copyright © 2010 Pearson Education, Inc.

Figure 15.19b Visual pathway to the brain and visual fields, inferior view.

Optic nerve

Optic chiasma Optic tract Lateral geniculate nucleus

Superior colliculus (sectioned)

Optic radiation

Corpus callosum (b) Photograph of human brain, with the right side dissected to reveal internal structures. Copyright © 2010 Pearson Education, Inc.

Which of the following structures is not involved in the processing of visual information? 1) 2) 3) 4)

Retina Thalamus Medulla oblongata Visual cortex in occipital lobe

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THE SPECIAL SENSES OLFACTION (SMELL)

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Figure 15.21a Olfactory receptors.

Olfactory epithelium

Olfactory tract Olfactory bulb

Nasal conchae

(a) Copyright © 2010 Pearson Education, Inc.

Route of inhaled air

Figure 15.21b Olfactory receptors.

Olfactory tract

Mitral cell (output cell) Glomeruli Olfactory bulb

Cribriform plate of ethmoid bone Filaments of olfactory nerve Olfactory gland

Lamina propria connective tissue Axon Basal cell Olfactory receptor cell

Olfactory epithelium

Supporting cell

Mucus (b) Copyright © 2010 Pearson Education, Inc.

Dendrite Olfactory cilia Route of inhaled air containing odor molecules

Figure 15.22 Olfactory transduction process.

1

Odorant binds to its receptor. Odorant

Adenylate cyclase

G protein (Golf)

Open cAMP-gated cation channel

Receptor GDP

2

Receptor activates G protein (Golf).

3

G protein activates adenylate cyclase.

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4

Adenylate cyclase converts ATP to cAMP.

5 cAMP opens a

cation channel allowing Na+ and Ca2+ influx and causing depolarization.

THE SPECIAL SENSES GUSTATION (TASTE)

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Figure 15.23 Location and structure of taste buds on the tongue.

Foliate papillae Epiglottis

Connective tissue Taste fibers of cranial nerve

Gustatory hair

Palatine tonsil Lingual tonsil Circumvallate papilla

Fungiform papillae (a) Taste buds are associated with fungiform, foliate, and circumvallate (vallate) papillae. Copyright © 2010 Pearson Education, Inc.

Stratified Basal Gustatory Taste squamous cells (taste) cells pore epithelium of tongue

Taste bud (b) Enlarged section of a circumvallate papilla.

(c) Enlarged view of a taste bud.

Figure 15.23a Location and structure of taste buds on the tongue.

Epiglottis Palatine tonsil Lingual tonsil Foliate papillae

Fungiform papillae (a) Taste buds are associated with fungiform, foliate, and circumvallate (vallate) papillae. Copyright © 2010 Pearson Education, Inc.

Figure 15.23b Location and structure of taste buds on the tongue.

Circumvallate papilla

Taste bud

(b) Enlarged section of a circumvallate papilla. Copyright © 2010 Pearson Education, Inc.

Figure 15.23c Location and structure of taste buds on the tongue.

Connective tissue Taste fibers of cranial nerve

Gustatory hair

Basal Gustatory Taste cells (taste) cells pore

Stratified squamous epithelium of tongue

(c) Enlarged view of a taste bud. Copyright © 2010 Pearson Education, Inc.

Figure 15.24 The gustatory pathway.

Gustatory cortex (in insula)

Thalamic nucleus (ventral posteromedial nucleus) Pons

Solitary nucleus in medulla oblongata Facial nerve (VII) Glossopharyngeal nerve (IX)

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Vagus nerve (X)

Gustation and olfaction use what kind of sensory receptors? 1) 2) 3) 4) 5)

Mechanoreceptors Chemoreceptors Photoreceptors Nociceptors Thermoreceptors

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THE SPECIAL SENSES HEARING & EQUILIBRIUM (BALANCE)

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Figure 15.25a Structure of the ear.

External ear

Middle Internal ear ear (labyrinth)

Auricle (pinna) Helix

Lobule

External acoustic meatus

(a) The three regions of the ear Copyright © 2010 Pearson Education, Inc.

Tympanic Pharyngotympanic membrane (auditory) tube

Figure 15.25b Structure of the ear.

Oval window (deep to stapes) Entrance to mastoid antrum in the epitympanic recess

Auditory ossicles

Malleus (hammer) Incu (anvil) Stapes (stirrup)

Tympanic membrane

Semicircular canals

Vestibule Vestibular nerve Cochlear nerve

Cochlea Round window

(b) Middle and internal ear Copyright © 2010 Pearson Education, Inc.

Pharyngotympanic (auditory) tube

Figure 15.26 The three auditory ossicles and associated skeletal muscles.

Malleus

Superior

Epitympanic recess Incus

Lateral Anterior View

Pharyngotympanic tube Tensor tympani muscle Copyright © 2010 Pearson Education, Inc.

Tympanic membrane (medial view)

Stapes

Stapedius muscle

The separation between the outer ear and inner ear is the… 1) 2) 3) 4)

Auricle Incus Oval window Tympanic membrane

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The spiral-shaped structure in the inner ear which contains receptors for hearing is the… 1) 2) 3) 4)

vestibule macula cochlea pharyngotympanic tube

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Figure 15.27 Membranous labyrinth of the internal ear.

Superior vestibular ganglion Inferior vestibular ganglion Temporal bone

Semicircular ducts in semicircular canals

Facial nerve Vestibular nerve

Anterior

Posterior Lateral Cochlear nerve Maculae

Cristae ampullares in the membranous ampullae Utricle in vestibule Saccule in vestibule

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Stapes in oval window

Spiral organ (of Corti) Cochlear duct in cochlea Round window

Figure 15.28a Anatomy of the cochlea.

Modiolus

Cochlear nerve, division of the vestibulocochlear nerve (VIII) Spiral ganglion

Osseous spiral lamina Vestibular membrane Cochlear duct (scala media) (a)

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Helicotrema

Figure 15.28b Anatomy of the cochlea.

Vestibular membrane Tectorial membrane Cochlear duct (scala media; contains endolymph)

Osseous spiral lamina

Scala vestibuli (contains perilymph)

Stria vascularis

Spiral organ (of Corti) Basilar membrane

(b) Copyright © 2010 Pearson Education, Inc.

Scala tympani (contains perilymph)

Spiral ganglion

Figure 15.28c Anatomy of the cochlea.

Tectorial membrane

Inner hair cell

Hairs (stereocilia)

Afferent nerve fibers

Outer hair cells

Supporting cells Fibers of cochlear nerve

(c) Copyright © 2010 Pearson Education, Inc.

Basilar membrane

Figure 15.28d Anatomy of the cochlea.

Inner hair cell

Outer hair cell

(d) Copyright © 2010 Pearson Education, Inc.

True or false: The organ of Corti senses sound waves when the tectorial membrane vibrates. 1) True 2) False

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The actual sensory receptor of hearing is the…

1) 2) 3) 4)

the cochlea hair cell the basilar membrane the tympanic membrane

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Air pressure

Figure 15.29 Sound: source and propagation.

Wavelength

Area of high pressure (compressed molecules) Area of low pressure (rarefaction) Crest

Trough Distance

Amplitude (a) A struck tuning fork alternately compresses and rarefies the air molecules around it, creating alternate zones of high and low pressure.

(b) Sound waves radiate outward in all directions. Copyright © 2010 Pearson Education, Inc.

Figure 15.30 Frequency and amplitude of sound waves.

Pressure

High frequency (short wavelength) = high pitch Low frequency (long wavelength) = low pitch

Time (s) (a) Frequency is perceived as pitch.

Pressure

High amplitude = loud Low amplitude = soft

Time (s) (b) Amplitude (size or intensity) is perceived as loudness. Copyright © 2010 Pearson Education, Inc.

Figure 15.30a Frequency and amplitude of sound waves.

Pressure

High frequency (short wavelength) = high pitch Low frequency (long wavelength) = low pitch

Time (s) (a) Frequency is perceived as pitch.

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Figure 15.30b Frequency and amplitude of sound waves.

Pressure

High amplitude = loud Low amplitude = soft

Time (s) (b) Amplitude (size or intensity) is perceived as loudness. Copyright © 2010 Pearson Education, Inc.

The “pitch” of a sound is determined by…

1) amplitude of a sound wave 2) frequency of a sound wave

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Figure 15.31a Pathway of sound waves and resonance of the basilar membrane.

Auditory ossicles Malleus Incus Stapes

Cochlear nerve Scala vestibuli Oval window Helicotrema

2

3

Scala tympani Cochlear duct Basilar membrane

1

Tympanic Round membrane window (a) Route of sound waves through the ear 1 Sound waves vibrate

3 Pressure waves created by

the tympanic membrane.

the stapes pushing on the oval window move through fluid in the scala vestibuli.

2 Auditory ossicles vibrate.

Pressure is amplified. Copyright © 2010 Pearson Education, Inc.

Sounds with frequencies below hearing travel through the helicotrema and do not excite hair cells. Sounds in the hearing range go through the cochlear duct, vibrating the basilar membrane and deflecting hairs on inner hair cells.

Figure 15.31b Pathway of sound waves and resonance of the basilar membrane.

Basilar membrane

High-frequency sounds displace the basilar membrane near the base.

Medium-frequency sounds displace the basilar membrane near the middle.

Low-frequency sounds displace the basilar membrane near the apex.

(b) Different sound frequencies cross the basilar membrane at different locations.

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Fibers of basilar membrane Apex (long, floppy fibers)

Base (short, stiff fibers)

Frequency (Hz)

Figure 15.32 Photo of cochlear hair cell with its precise array of stereocilia.

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“Resonance” refers to…

1) Something really making sense 2) The vestibule and cochlea vibrating at the same time and same frequency 3) The response of fibers of a particular length vibration with sound waves of a particular frequency. 4) Fibers of a particular length vibrating with sound waves of a particular amplitude. Copyright © 2010 Pearson Education, Inc.

Figure 15.33 The auditory pathway.

Medial geniculate nucleus of thalamus

Primary auditory cortex in temporal lobe Inferior colliculus Lateral lemniscus Superior olivary nucleus (pons-medulla junction)

Midbrain

Cochlear nuclei

Vibrations

Medulla

Vestibulocochlear nerve Vibrations

Spiral ganglion of cochlear nerve Bipolar cell Spiral organ (of Corti)

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Which of these structures is NOT involved in carrying information from the vestibulocochlear nerve? 1) 2) 3) 4)

thalamus Auditory cortex pons Medulla oblongata

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Figure 15.34 Structure of a macula.

Kinocilium

Stereocilia

Otoliths Otolithic membrane Hair bundle

Macula of utricle Macula of saccule

Hair cells

Supporting cells Vestibular nerve fibers Copyright © 2010 Pearson Education, Inc.

Figure 15.35 The effect of gravitational pull on a macula receptor cell in the utricle.

Otolithic membrane Kinocilium Stereocilia

Hyperpolarization Receptor potential Nerve impulses generated in vestibular fiber

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Depolarization When hairs bend toward the kinocilium, the hair cell depolarizes, exciting the nerve fiber, which generates more frequent action potentials.

When hairs bend away from the kinocilium, the hair cell hyperpolarizes, inhibiting the nerve fiber, and decreasing the action potential frequency.

Figure 15.36a–b Location, structure, and function of a crista ampullaris in the internal ear.

Cupula Crista ampullaris

Endolymph

Hair bundle (kinocilium plus stereocilia) Hair cell Crista Membranous ampullaris labyrinth Fibers of vestibular nerve (a) Anatomy of a crista ampullaris in a semicircular canal

Cupula

(b) Scanning electron micrograph of a crista ampullaris (200x) Copyright © 2010 Pearson Education, Inc.

Supporting cell

Figure 15.36c Location, structure, and function of a crista ampullaris in the internal ear.

Section of ampulla, filled with endolymph Cupula

Fibers of vestibular nerve

At rest, the cupula stands upright. (c) Movement of the cupula during rotational acceleration and deceleration Copyright © 2010 Pearson Education, Inc.

Flow of endolymph

During rotational acceleration, endolymph moves inside the semicircular canals in the direction opposite the rotation (it lags behind due to inertia). Endolymph flow bends the cupula and excites the hair cells.

As rotational movement slows, endolymph keeps moving in the direction of the rotation, bending the cupula in the opposite direction from acceleration and inhibiting the hair cells.

Rotational movement is detected by…

1) Macula in utricle 2) Macula in saccule 3) Cupula & crista ampullaris attached to semicircular canals 4) All of the above

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Figure 15.37 Pathways of the balance and orientation system.

Input: Information about the body’s position in space comes from three main sources and is fed into two major processing areas in the central nervous system.

Cerebellum

Somatic receptors (from skin, muscle and joints)

Visual receptors

Vestibular receptors

Vestibular nuclei (in brain stem)

Central nervous system processing

Oculomotor control (cranial nerve nuclei III, IV, VI)

Spinal motor control (cranial nerve XI nuclei and vestibulospinal tracts)

(eye movements)

(neck movements)

Output: Fast reflexive control of the muscles serving the eye and neck, limb, and trunk are provided by the outputs of the central nervous system. Copyright © 2010 Pearson Education, Inc.