PPT 2 Senses 16 2 Hearing and Equilibrium hearing a response to vibrating air molecules equilibrium the sense of motion body orientation and balance both senses reside in the inner ear ID: 774679
Download Presentation The PPT/PDF document " Sense of Hearing and Equilibrium and Si..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Sense of Hearing and Equilibrium and Sight
PPT #2 Senses
Slide216-2
Hearing and Equilibrium
hearing –
a response to vibrating air molecules
equilibrium
– the sense of motion, body orientation, and balance
both senses reside in the
inner ear
, a maze of fluid-filled passages and sensory cells
fluid is set in motion and how the sensory cells convert this motion into an informative pattern of action potentials
Slide316-3
The Nature of Sound
sound – any audible vibration of moleculesa vibrating object pushes on air moleculesin turn push on other air moleculesair molecules hitting eardrum cause it to vibration
Outer ear
Middle ear
Inner ear
Helix
Stapes
Incus
Malleus
Ossicles:
Auricle
Lobule
Semicircular ducts
Cochlear nerve
Cochlea
Round window
Auditory tube
Oval window
Vestibular nerve
Vestibule
Tympanic cavity
Tensor tympani
muscle
Tympanic
membrane
Auditory
canal
Figure 16.11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide416-4
Pitch and Loudness
pitch – our sense of whether a sound is ‘high’ or ‘low’determined by the frequency - cycles/sec – cps or hertz, Hzhuman hearing range is 20 Hz - 20,000 Hz (cycles/sec)speech is 1500-5000 where hearing is most sensitivehearing loss with age is 250 to 2,050 Hzloudness – the perception of sound energy, intensity, or amplitude of the vibrationexpressed in decibels (dB)prolonged exposure to sounds > 90dB can cause damageCan you hear me now????? Try this…http://onlinetonegenerator.com/hearingtest.html
Figure 16.9
Frequency (hertz)
Loudness (decibels)
Threshold of hearing
All sound
Music
Speech
Threshold of pain
0
20
40
60
80
100
120
20
50
100
200
500
1,000
2,000
5,000
10,000
20,000
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide5Slide6Anatomy of Ear
ear has three sections outer, middle, and inner earfirst two are concerned only with the transmission of sound to the inner earinner ear – vibrations converted to nerve signals
16-6
Outer ear
Middle ear
Inner ear
Helix
Stapes
Incus
Malleus
Ossicles:
Auricle
Lobule
Semicircular ducts
Cochlear nerve
Cochlea
Round window
Auditory tube
Oval window
Vestibular nerve
Vestibule
Tympanic cavity
Tensor tympani
muscle
Tympanic
membrane
Auditory
canal
Figure 16.11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide7Outer Ear
Only two structures
Actual “ear” that we see is the
pinna
Opens to a tube called
auditory cannal
Both are designed to collect logitudinal compression and rarefaction waves
Slide816-8
Anatomy of Middle Ear
Figure 16.11
Outer ear
Middle ear
Inner ear
Helix
Stapes
Incus
Malleus
Ossicles:
Auricle
Lobule
Semicircular ducts
Cochlear nerve
Cochlea
Round window
Auditory tube
Oval window
Vestibular nerve
Vestibule
Tympanic cavity
Tensor tympani
muscle
Tympanic
membrane
Auditory
canal
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide916-9
Middle Ear
middle ear
- located in the air-filled tympanic cavity in temporal bone
tympanic membrane (eardrum
) – closes the inner end of the auditory canal
separates it from the middle ear
vibrates
freely in response to sound
innervated by sensory branches of the
vagus
and trigeminal nerves
highly sensitive to pain
tympanic cavity
contains
auditory
ossicles
auditory (
eustachian
) tube
connects middle ear cavity to nasopharynx
equalizes air pressure on both sides of tympanic membrane
normally flattened and closed and swallowing and yawning opens it
allows throat infections to spread to the middle ear
auditory
ossicles
bones…
3 smallest in your body
malleus
- attached to inner surface of tympanic membrane
incus
- articulates in between malleus and stapes
stapes
- footplate rests on oval window – inner ear begins
Slide1016-10
Middle-Ear Infection
Otitis media
(middle ear infection) is common in children
auditory tube is short and horizontal
infections easily spread from throat to tympanic cavity and mastoid air cells
Slide11(a)
Temporal
bone
16-
11
Anatomy of Inner Ear
Figure 16.12a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide1216-12
Inner (Internal) Ear
bony labyrinth - passageways in temporal bonemembranous labyrinth - fleshy tubes lining the bony labyrinthfilled with endolymph - similar to intracellular fluidfloating in perilymph - similar to cerebrospinal fluid
Figure 16.12c
Scala vestibuli
Scala tympani
Cochlear duct
Utricle
Ampulla
Semicircular canal
Posterior
Anterior
Semicircular ducts:
Dura mater
Saccule
Lateral
(c)
Endolymphatic
sac
Vestibule:
Secondary tympanic membrane
in round window
Stapes
in oval window
Tympanic
membrane
Temporal bone
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide13Inner Ear
Actual center where sound waves are processed
Has fluid filled chambers called
semicircular canals
, responsible for spatial orientation
The
cochlea
is the hearing
center
Connected to
auditory nerve
, which relays info to
auditory complex
in cerebrum
Slide1416-14
Details of Inner Ear
labyrinth - vestibule and three semicircular ductscochlea - organ of hearing 2.5 coils around an screwlike axis of spongy bone, the modiolus – threads of the screw form a spiral platform that supports the fleshy tube of the cochlea
Figure 16.12b
(b)
Cochlear nerve
Facial nerve
Saccule
Utricle
Cochlea
Posterior
Lateral
Anterior
Semicircular ducts:
Ampullae
Spiral ganglion
of cochlea
Vestibular
ganglion
Endolymphatic
sac
Vestibular nerve
Vestibule:
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide1516-15
Physiology of Hearing - Middle Ear
tympanic
membrane and tympanic space
ossicles
and their muscles have a protective function
lessen the transfer of energy to the inner ear
middle
ear muscles also help to coordinate speech with hearing
dampens the sound of your own speech
Slide1616-16
Stimulation of Cochlear Hair Cells
vibration of ossicles causes vibration of basilar membrane under hair cellsas often as 20,000 times per secondhair cells move with basilar membranehttps://www.youtube.com/watch?v=0jyxhozq89g
Figure 16.15
Outer ear
Middle ear
Inner ear
Air
Fluid
Malleus
Incus
Stapes
Tympanic
membrane
Auditory
tube
Oval
window
Basilar
membrane
Secondary
tympanic
membrane
(in round
window)
Sound
wave
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide1716-17
Deafness
deafness
– hearing loss
conductive deafness -
conditions interfere with transmission of vibrations to inner ear
damaged tympanic membrane, otitis media, blockage of auditory canal, and otosclerosis
otosclerosis
- fusion of auditory ossicles that prevents their free vibration
sensorineural (nerve) deafness
- death of hair cells or any nervous system elements concerned with hearing
factory workers, musicians and construction workers
Slide18(b)
Cochlear nerve
Facial nerve
Saccule
Utricle
Cochlea
Posterior
Lateral
Anterior
Semicircular ducts:
Ampullae
Spiral ganglion
of cochlea
Vestibular
ganglion
Endolymphatic
sac
Vestibular nerve
Vestibule:
16-
18
Innervation of Internal Ear
vestibular ganglia
-
visible lump in vestibular nerve
spiral ganglia
- buried in modiolus of cochlea
Figure 16.12b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide1916-19
Auditory Projection Pathway
sensory fibers begin at the
bases of the hair cells
somas form the
spiral ganglion
around the
modiolus
axons lead away from the cochlea as the
cochlear nerve
joins with the vestibular nerve to form the
vestibulocochlear nerve
, Cranial Nerve VIII
each ear sends nerve fibers to both sides of the
pons…..
end
in cochlear nuclei
Slide2016-20
Auditory Projection Pathway
fibers ascend to the inferior colliculi of the midbrain
helps to locate the origin of the sound, processes fluctuation in pitch, and mediate the startle response and rapid head turning in response to loud noise
third-order neurons begin in the inferior colliculi and lead to the thalamus
fourth-order neurons complete the pathway from thalamus to primary auditory complex
involves four neurons instead of three unlike most sensory pathways
primary auditory cortex lies in the superior margin of the temporal lobe
site of conscious perception of sound
Slide2116-21
Auditory Pathway
Figure 16.18a
Tympanic reflex
Cranial nerve VIII
Cochlear tuning
Cochlea
(a)
Primary
auditory
cortex
Temporal
lobe of
cerebrum
Medial
geniculate
nucleus of
thalamus
Auditory
reflex (head
turning)
Neck
muscles
Inferior colliculus
of midbrain
Superior olivarynucleus of pons
Cranial nervesV3 and VII
Tensor tympani andstapedius muscles
Cochlear nucleiof pons
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide22Thalamus
Cochlea
(b)
Cochlear nucleus
Medulla oblongata
Inferior colliculus
Cranial
nerve VIII
Primary auditory
cortex
Superior olivary
nucleus
16-
22
Auditory Processing Centers
Figure 16.18b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide2316-23
Equilibrium
equilibrium
– coordination, balance, and orientation in three-dimensional space
vestibular apparatus
– constitutes receptors for equilibrium
three semicircular ducts
detect only angular acceleration
two chambers
anterior saccule and posterior utricle
responsible for static equilibrium and linear acceleration
static equilibrium
– the perception of the orientation of the head when the body is stationary
dynamic equilibrium
- perception of motion or acceleration
linear acceleration
-
change in velocity in a straight line (elevator)
angular acceleration
-
change in rate of rotation (car turns a corner
)
https://www.youtube.com/watch?v=YMIMvBa8XGs
Slide24Sense of sight
Slide25Frontal bone
Cornea
Tarsal plate
Conjunctiva
(a)
Tarsal glands
Levator palpebrae
superioris muscle
Orbicularis
oculi muscle
Superior rectus
muscle
Lateral rectus
muscle
Inferior rectus
muscle
16-
25
Conjunctiva
conjunctiva
– a transparent mucous membrane that lines eyelids and covers anterior surface of eyeball, except cornea
richly innervated and vascular (heals quickly)
secretes a thin mucous film that prevents the eyeball from drying
Figure 16.23a
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide2616-26
Anatomy of the Eyeball
three principal components of the eyeballthree layers (tunics) that form the wall of the eyeballoptical component – admits and focuses lightneural component – the retina and optic nerve
Sclera
Choroid
Retina
Macula lutea
Optic nerve
Fovea centralis
Vitreous body
Pupil
Cornea
Iris
Ciliary body
Ora serrata
Lens
Hyaloid canal
Optic disc
(blind spot)
Central artery
and vein
of retina
Suspensory
ligament
Anterior
chamber
Posterior
chamber
Figure 16.25
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide2716-27
Tunics(Layers) of the Eyeball
tunica
fibrosa
– outer fibrous layer
sclera
– dense, collagenous white of the eye
cornea
- transparent area of sclera that admits light into eye
tunica
vasculosa
(uvea) – middle vascular layer
choroid
– highly vascular, deeply pigmented layer behind retina
ciliary body
– extension of choroid that forms a muscular ring around lens
supports lens and iris
secretes aqueous humor
iris
- colored diaphragm controlling size of pupil, its central opening
melanin in
chromatophores
of iris - brown or black eye color
reduced melanin – blue, green, or gray color
tunica
interna
- retina and beginning of optic nerve
Slide2816-28
Optical Components
transparent elements that admit light rays, refract (bend) them, and focus images on the retina
cornea
transparent cover on anterior surface of eyeball
aqueous humor
serous fluid posterior to cornea, anterior to lens
produced
and reabsorbed at same rate
lens
lens fibers
– flattened, tightly compressed, transparent cells that form lens
changes
shape to help focus light
Slide29Iris
Lens
Anterior chamber
Cornea
Ciliary body:
Scleral
venous sinus
Ciliary
process
Ciliary
muscle
Posterior
chamber
Vitreous
body
16-
29
Aqueous Humor
released by ciliary body into posterior chamber, passes through pupil into anterior chamber - reabsorbed into canal of
Schlemm
Figure 16.26
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide3016-30
Neural Components
Figure 16.28a
(a)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
© Lisa Klancher
Slide3116-31
Neural Components
includes retina and optic nerve
retina
-
made of neurons and photo receptors
forms as an outgrowth of the diencephalon
attached to the rest of the eye only at optic disc and at
ora
serrata
(optic
blinnd
spot)!!
pressed against rear of eyeball by vitreous humor
detached retina causes blurry areas in field of vision and leads to blindness
examine retina with
opthalmoscope
macula
lutea
– patch of cells on visual axis of eye
fovea
centralis
– pit in center of macula
lutea
blood vessels
of the retina
Slide32Fovea centralis
Optic disc
(b)
Venule
Arteriole
Macula lutea
16-
32
Ophthalmoscopic Exam of Eye
macula lutea
- cells on visual axis of eye (3 mm)
fovea centralis
- center of macula; finely detailed images due to packed receptor cells
direct evaluation of blood vessels
Figure 16.28b
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide3316-33
Test for Blind Spot
optic disk - blind spot optic nerve exits posterior surface of eyeballno receptor cells at that locationblind spot - use test illustration aboveclose eye, stare at X and red dot disappearsvisual filling - brain fills in green bar across blind spot area
Figure 16.29
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide3416-34
Formation of an Image
light passes through lens to form tiny inverted image on retina
conversion of light energy into action potentials occurs in the retina
neural components of the retina from the rear of the eye forward
photoreceptor cells – absorb light and generate a chemical or electrical signal
rods, cones, and certain ganglion cells
only rods and cones produce visual images
bipolar cells – synapse with rods and cones and are first-order neurons of the visual pathway
ganglion cells – largest neurons in the retina and are the second-order neurons of the visual pathway
Slide3516-35
Generating Visual Signals
Figure 16.38
1
1
2
3
4
5
2
3
4
5
Rod cell
Bipolar cell
Ganglion cell
Rhodopsin
absorbs light
(a) In the dark
(b) In the light
Rhodopsin
absorbs no light
Rod cell releases
glutamate
Bipolar cell
inhibited
No synaptic
activity here
No signal in
optic nerve fiber
Glutamate
secretion
ceases
Bipolar cell
no longer
inhibited
Bipolar cell
releases
neurotransmitter
Signal inoptic nerve fiber
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide3616-36
Photoreceptor Cells
light absorbing cells derived from same stem cells as ependymal cells of the brainrod cells (night - scotopic vision or monochromatic vision)cone cells (color, photopic, or day vision)
Figure 16.35b
Stalk
Mitochondria
Nucleus
Rod
Cone
(b)
Outer
segment
Inner
segment
Cell
body
Synaptic
vesicles
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide3716-37
Generating Optic Nerve Signals
in dark, rods steadily release the neurotransmitter, glutamate from basal end of cell
when rods absorb light, glutamate secretion ceases
bipolar cells sensitive to these on and off pulses of glutamate secretion
some bipolar cells inhibited by glutamate and excited when secretion stops
these cells excited by rising light intensities
other bipolar cells are excited by glutamate and respond when light intensity drops
when bipolar cells detect fluctuations in light intensity, they stimulate ganglion cells directly or indirectly
ganglion cells are the only retinal cells that produce action potentials
ganglion cells respond to the bipolar cells with rising and falling firing frequencies
via optic nerve, these changes provide visual signals to the brain
Slide3816-38
Visual Projection Pathway
bipolar cells of retina are
first-order neurons
retinal ganglion cells are
second-order neurons
whose axons form optic nerve
two optic nerves combine to form
optic chiasm
half the fibers cross over to the opposite
sides
of the brain
to
form
optic tracts
right cerebral hemisphere sees objects in the left visual field because their images fall on the right half of each retina
each side of brain sees what is on
the side
where it has motor control over limbs
Slide39Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Optic tract
Left eye
Right eye
Optic radiation
Uncrossed
(ipsilateral)
fiber
Crossed
(contralateral)
fiber
Occipital lobe
(visual cortex)
Fixation
point
Optic
nerve
Optic
chiasm
Pretectal
nucleus
Lateral
geniculate
nucleus of
thalamus
Superior
colliculus
16-
39
Visual Projection Pathway
Figure 16.43
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide4016-40
Visual Information Processing
primary visual cortex
is connected by association tracts to
visual association areas
in parietal and temporal lobes which process retinal data from occipital lobes
object location, motion, color, shape, boundaries
store visual memories (recognize printed words)
Slide4116-41
Innervation of Extrinsic Eye Muscles
superior, inferior, medial and lateral rectus muscles move the eye up, down, medially & laterallysuperior and inferior oblique mm. turn the “twelve o’clock pole” of each eye toward or away from the noseorbital fat – surrounds sides and back of eye, cushions eye and allows free movement, protects blood vessels, and nerves
Figure 16.24c
(c) Frontal view
Oculomotor nerve (III)
Trochlear nerve (IV)
Abducens nerve (VI)
Superior
oblique
muscle
Lateral
rectus
muscle
Levator palpebrae
superioris muscle
Superior rectus
muscle
Medial rectus
muscle
Inferior rectus
muscle
Inferior oblique
muscle
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Slide4216-42
Extrinsic Eyes Muscles
6 muscles attached to exterior surface of eyeballsuperior, inferior, lateral, and medial rectus muscles, superior and inferior oblique musclesinnervated by cranial nerves III, IV and VI
Figure 16.24a
Figure 16.24b
(a) Lateral view
Superior oblique
Muscles:
Superior rectus
Lateral rectus
Medial rectus
Inferior oblique
Inferior rectus
Trochlea
Optic nerve
(b) Superior view
Muscles:
Medial rectus
Trochlea
Superior rectus
Inferior rectus
Muscles:
Superior oblique
Levator palpebrae
superioris (cut)
Superior oblique
tendon
Lateral rectus
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.