HW page 9: Matching Eye Disorders

PreLab 5

HOMEWORK DUE IN LAB 5

Hearing and Equilibrium

THE SPECIAL SENSES

The organ of hearing and equilibrium

Cranial nerve VIII - Vestibulocochlear

Regions

External ear

Middle ear

Internal ear (labyrinth)

THE EAR

Figure 15.25a

External

acoustic

meatus

Auricle

(pinna)

(a) The three regions of the ear

Helix

Lobule

Pharyngotympanic

(auditory) tube

Tympanic

membrane

External

ear

Middle

ear

Internal ear

(labyrinth)

Copyright © 2010 Pearson Education, Inc. Figure 15.26

Pharyngotym-

panic tube

Tensor

tympani

muscle

Tympanic

membrane

(medial view)

Stapes

Malleus

View

Superior

Anterior

Lateral

Incus Epitympanic

recess

Stapedius

muscle

Middle Ear

Auditory tube

Connects the middle ear to the nasopharynx

Equalizes pressure

Opens during swallowing and yawning

Otitis media

MIDDLE EAR

Contains functional organs for hearing & equilibrium

Bony labyrinth

Membranous labyrinth

INNER EAR

Figure 15.27

Anterior

Semicircular

ducts in

semicircular

canals

Posterior

Lateral

Cristae ampullares

in the membranous

ampullae

Utricle in

vestibule

Saccule in

vestibule Stapes in

oval window

Temporal bone

Facial nerve

Vestibular

nerve

Superior vestibular ganglion

Inferior vestibular ganglion

Cochlear

nerve

Maculae

Spiral organ

(of Corti) Cochlear

duct

in cochlea

Round

window

Three distinct regions

Vestibule

Gravity

Head position

Linear acceleration and deceleration

Semicircular canals

Angular acceleration and deceleration

Cochlea

Vibration

INNER EAR - BONY LABYRINTH

Figure 15.27

Anterior

Semicircular

ducts in

semicircular

canals

Posterior

Lateral

Cristae ampullares

in the membranous

ampullae

Utricle in

vestibule

Saccule in

vestibule Stapes in

oval window

Temporal bone

Facial nerve

Vestibular

nerve

Superior vestibular ganglion

Inferior vestibular ganglion

Cochlear

nerve

Maculae

Spiral organ

(of Corti) Cochlear

duct

in cochlea

Round

window

The cochlea

A spiral, conical, bony chamber Vestibular canal (scala vestibuli)

Cochlear duct (scala media)

Tympanic canal (scala tympani)

INNER EAR

Figure 15.28a

(a) Helicotrema

Modiolus Cochlear nerve, division of the vestibulocochlear nerve (VIII)

Cochlear duct

(scala media)

Spiral ganglion

Osseous spiral lamina

Vestibular membrane

Cavity of the cochlea is divided into 3 chambers

Vestibular canal (scala vestibuli)

Vestibular membrane

Cochlear duct (scala media)

Basilar membrane supporting Organ of Corti

Tympanic canal (scala tympani)

INNER EAR

Copyright © 2010 Pearson Education, Inc. Figure 15.28b

(b)

Cochlear duct (scala media; contains endolymph)

Tectorial membrane

Vestibular membrane

Scala vestibuli (contains perilymph)

Scala tympani

(contains

perilymph) Basilar

membrane

Spiral organ

(of Corti)

Stria

vascularis

Spiral

ganglion

Osseous spiral lamina

Figure 15.28c

(c)

Tectorial membrane Inner hair cell

Outer hair cells

Hairs (stereocilia) Afferent nerve

fibers

Basilar

membrane

Fibers of cochlear nerve

Supporting cells

Organ of Corti

Transduction of sound

Mechanical energy in middle ear

Fluid pressure wave in inner ear

Nerve impulse

PHYSIOLOGY OF HEARING

Sounds set up vibrations in air that beat against the eardrum

that pushes a chain of tiny bones that press fluid in the

internal ear against membranes that set up shearing forces

that pull on the tiny hair cells that stimulate nearby neurons

that give rise to the impulses that travel to the brain – and

you hear.

(This is from your textbook)

PHYSIOLOGY OF HEARING IN A NUTSHELL

Figure 15.29

Area of

high pressure

(compressed

molecules)

Crest

Trough

Distance Amplitude

Area of

low pressure

(rarefaction)

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.

Wavelength

Air p

re

ssu

re

Copyright © 2010 Pearson Education, Inc. Figure 15.30

Time (s)

(a) Frequency is perceived as pitch.

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

(b) Amplitude (size or intensity) is perceived as loudness.

High amplitude = loud Low amplitude = soft

Time (s)

Pre

ssu

re

P

re

ssu

re

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

5 Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

5

6

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

5

6

7

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

5

6

7 8

8

Scala

vestibuli

Cochlear duct

(contains endolymph)

Scala

tympani

Perilymph

Basilar

membrane

Cochlea

Sound waves

Helicotrema Stapes vibrating

in oval window Malleus Incus

External auditory

canal

Tympanic

membrane

Secondary tympanic

membrane vibrating

in round window Auditory tube

Vestibular membrane

Middle ear

Tectorial membrane

Spiral organ

(organ of Corti)

1 2

3 4

5

6

7 8

8

9

Copyright © 2010 Pearson Education, Inc. Figure 15.31a

Scala tympani

Cochlear duct

Basilar

membrane

1 Sound waves vibrate

the tympanic membrane.

2 Auditory ossicles vibrate.

Pressure is amplified.

3 Pressure waves created by

the stapes pushing on the oval

window move through fluid in

the scala vestibuli.

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.

Malleus Incus

Auditory ossicles

Stapes

Oval

window

Scala vestibuli

Helicotrema

Cochlear nerve

3 2

1

Round

window

Tympanic

membrane (a) Route of sound waves through the ear

Copyright © 2010 Pearson Education, Inc. Figure 15.31b

Fibers of basilar membrane

(b) Different sound frequencies cross the

basilar membrane at different locations.

Medium-frequency sounds displace

the basilar membrane near the middle.

Low-frequency sounds displace the

basilar membrane near the apex.

Base

(short,

stiff

fibers)

Frequency (Hz)

Apex

(long,

floppy

fibers)

Basilar membrane

High-frequency sounds displace

the basilar membrane near the base.

Copyright © 2010 Pearson Education, Inc. Figure 15.28c

(c)

Tectorial membrane Inner hair cell

Outer hair cells

Hairs (stereocilia) Afferent nerve

fibers

Basilar

membrane

Fibers of cochlear nerve

Supporting cells

Figure 15.33

Medial geniculate

nucleus of thalamus

Primary auditory

cortex in temporal lobe

Inferior colliculus

Lateral lemniscus

Superior olivary nucleus

(pons-medulla junction)

Spiral organ (of Corti)

Bipolar cell

Spiral ganglion of cochlear nerve

Vestibulocochlear nerve

Medulla

Midbrain

Cochlear nuclei

Vibrations

Vibrations

Timing comparison

Side nearest sound detects sound first

Comparison of volume

High pitched = blocked by head

Low pitched = curve around head

LOCALIZATION OF SOUND

Conductive deafness Interference in movement of middle ear bones

Impacted earwax, perforated eardrum or otosclerosis of the ossicles

Sensorineural deafness Damage to the neural structures

Aging, prolonged exposure to loud sounds

ABNORMALITIES OF HEARING

Otitis media

ABNORMALITIES OF HEARING

Otosclerosis

ABNORMALITIES OF HEARING

Meniere’s Disease

ABNORMALITIES OF HEARING

Tinnitus

ABNORMALITIES OF HEARING

Information about position and movement of head

Vestibular apparatus

Utricle

Saccule

Semi-circular canals

PHYSIOLOGY OF EQUILIBRIUM

Vesibule

Figure 15.34

Macula of

saccule

Otoliths

Hair bundle

Kinocilium

Stereocilia Otolithic

membrane

Vestibular

nerve fibers

Hair cells

Supporting

cells

Macula of

utricle

Vestibular Apparatus

Maculae are

perpendicular

to one another

Macula

Utricle

Horizontal movements

Tilting the head side to side

Saccule

Vertical movements

VESTIBULE

Crista ampullaris

Sensory receptor for dynamic equilibrium

One in the ampulla of each semicircular canal

Major stimuli are rotatory movements

SEMI-CIRCULAR CANALS

Copyright © 2010 Pearson Education, Inc. Figure 15.36a–b

Fibers of vestibular nerve

Hair bundle (kinocilium

plus stereocilia)

Hair cell

Supporting

cell

Membranous

labyrinth

Crista

ampullaris

Crista

ampullaris

Endolymph

Cupula

Cupula

(a) Anatomy of a crista ampullaris in a

semicircular canal

(b) Scanning electron

micrograph of a

crista ampullaris

(200x)

Conflicts between eye movements and equilibrium

Nystagmus

Slow component

Fast component

MOTION SICKNESS