chapter 18 218/martini ppt... · introduction •sensory information arrives at the cns...
TRANSCRIPT
Lecture Presentation by
Steven Bassett
Southeast Community College
Chapter 18
The Nervous
System
General and
Special Senses
© 2015 Pearson Education, Inc.
Introduction
• Every plasmalemma functions as a receptor for
the cell
• Plasmalemma has receptors specific for:
• Chemical stimuli
• Electrical stimuli
• Mechanical stimuli
• Not all plasmalemmae have the same receptor
sites
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Introduction
• Sensory information arrives at the CNS
• Information is “picked up” by sensory receptors
• Sensory receptors are the interface between the
nervous system and the internal and external
environment
© 2015 Pearson Education, Inc.
Introduction
• Categories of Senses
• General senses
• Refers to temperature, pain, touch, pressure,
vibration, and proprioception
• Special senses
• Refers to smell, taste, balance, hearing, and vision
• Special sense receptors are located in complex
sense organs
• Examples are: eyes, ears, and taste buds
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Receptors
• Each receptor has a characteristic sensitivity
• This leads to receptor specificity
• Specificity is due to the structure of the receptor
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Receptors
• Examples of Specificity
• Free nerve endings are the simplest receptors
• These respond to a variety of stimuli
• Receptors of the retina
• Very specific and only respond to light
• The area monitored by the receptor cell is the
receptive field
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Receptors
• Receptive Fields
• Large receptive fields have receptors spread far
apart, which makes it difficult to localize a stimulus
• Small receptive fields have receptors close
together, which makes it easy to localize a
stimulus
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Figure 18.1 Receptors and Receptive Fields
© 2015 Pearson Education, Inc.
Receptive
field 1Receptive
field 2
Receptors
• Interpretation of Sensory Information
• Information is relayed from the receptor to
a specific neuron in the CNS
• Each pathway carries information concerning a
specific sensation
• The identity of the active neuron indicates:
• Location of the stimulus
• Nature of the stimulus
© 2015 Pearson Education, Inc.
Interpretation of Sensory Information
• Classification of Receptors
• Tonic receptors
• Always active
• Photoreceptors of the eye and receptors that
constantly monitor body position
• Phasic receptors
• Normally inactive but become active when
necessary (for short periods of time)
• Touch and pressure receptors of the skin (for
example)
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Receptors
• Central Processing and Adaptation
• Adaptation
• Reduction in sensitivity due to a constant stimulus
• Peripheral adaptation
• Receptors respond strongly at first and then
decline
• Central adaptation
• Adaptation within the CNS
• Consciously aware of a stimulus, which quickly
disappears
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The General Senses
• Classification of the General Senses
• One classification scheme:
• Exteroceptors
• Provide information about the external environment
• Proprioceptors
• Provide information about the position of the body
• Interoceptors
• Provide information about the inside of the body
© 2015 Pearson Education, Inc.
The General Senses
• Classification of the General Senses
• Another classification scheme:
• Nociceptors
• Respond to the sensation of pain
• Thermoreceptors
• Respond to changes in temperature
• Mechanoreceptors
• Activated by physical distortion of cell membranes
• Chemoreceptors
• Monitor the chemical composition of body fluids
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The General Senses
• Nociceptors
• Known as pain receptors
• Associated with free nerve endings and large
receptor fields
• This makes it difficult to “pinpoint” the location of
the origin of the pain
• There are three types
• Receptors sensitive to extreme temperatures
• Receptors sensitive to mechanical damage
• Receptors sensitive to chemicals
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The General Senses
• Nociceptors
• Fast pain
• Sensations reach the CNS fast
• Associated with pricking pain or cuts
• Slow pain
• Sensations reach the CNS slowly
• Associated with burns or aching pains
• Referred pain
• Sensations reach the spinal cord via the dorsal
roots
• Some visceral organ pain sensations may reach
the spinal cord via the same dorsal root
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Figure 18.2 Referred Pain
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Liver and
gallbladder
Heart
Stomach
Small
intestine
Appendix
Colon
Ureters
The General Senses
• Thermoreceptors
• Found in the dermis, skeletal muscles, liver, and
hypothalamus
• Cold receptors are more numerous than hot
receptors
• Exist as free nerve endings
• These are phasic receptors
• These are very active when the temperature
changes, but quickly adapt to a stable temperature
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The General Senses
• Mechanoreceptors
• Receptors that are sensitive to stretch,
compression, twisting, or distortion of the
plasmalemmae
• There are three types
• Tactile receptors
• Baroreceptors
• Proprioceptors
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The General Senses
• Mechanoreceptors
• Tactile receptors
• Provide sensations of touch, pressure, and
vibrations
• Unencapsulated tactile receptors
• Free nerve endings, tactile disc, and root hair
plexus
• Encapsulated tactile receptors
• Tactile corpuscle, Ruffini corpuscle, and
lamellated corpuscle
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The General Senses
• Mechanoreceptors
• Unencapsulated tactile receptors
• Free nerve endings are common in the dermis
• Tactile discs are in the stratum basale layer
• Root hair plexus monitors distortions and
movements of the body surface
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Figure 18.3a Tactile Receptors in the Skin
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Hair Merkel cells and
tactile discsTactile
corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Free nerve endings.a
Figure 18.3b Tactile Receptors in the Skin
© 2015 Pearson Education, Inc.
Hair Merkel cells and
tactile discsTactile
corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Merkel cells
Tactile disc
Merkel cells and
tactile discs.b
Figure 18.3c Tactile Receptors in the Skin
© 2015 Pearson Education, Inc.
Hair Merkel cells and
tactile discsTactile
corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Free nerve endings
of root hair plexus.
c
The General Senses
• Mechanoreceptors
• Encapsulated tactile receptors
• Tactile corpuscle
• Common on eyelids, lips, fingertips, nipples, and
genitalia
• Ruffini corpuscle
• In the dermis, sensitive to pressure and distortion
• Lamellated corpuscle
• Consists of concentric cellular layers / sensitive to
vibrations
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Figure 18.3d Tactile Receptors in the Skin
© 2015 Pearson Education, Inc.
Hair Merkel cells and
tactile discsTactile
corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Tactile
corpuscle Epidermis
Dermis
Capsule
Accessory
cells
Dendrites
Sensory
nerve fiber
Tactile corpuscle; the capsule
boundary in the micrograph is
indicated by a dashed line.
d
Tactile corpuscle LM x 550
Figure 18.3e Tactile Receptors in the Skin
© 2015 Pearson Education, Inc.
Hair Merkel cells and
tactile discs
Tactile
corpuscleFree nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Capsule
Dendrites
Collagen
fibers
Sensory
nerve fiber
Ruffini corpuscle.e
Figure 18.3f Tactile Receptors in the Skin
© 2015 Pearson Education, Inc.
Hair Merkel cells and
tactile discsTactile
corpuscle
Free nerve
ending
Ruffini corpuscle
Lamellated corpuscle
Root hair plexus
Sensory
nerves
Dermis
Dendritic process
Accessory cells
(specialized fibrocytes)
Concentric layers (lamellae)
of collagen fibers
separated by fluid
Lamellated corpuscle
Concentric layers
(lamellae) of
collagen fibers
separated by fluid
Dendritic
process
Lamellated corpuscle.
LM x 125
f
The General Senses
• Mechanoreceptors
• Baroreceptors
• Stretch receptors that monitor changes in the
stretch of organs
• Location:
• Stomach
• Small intestine
• Urinary bladder
• Carotid artery
• Lungs
• Large intestine
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Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions
© 2015 Pearson Education, Inc.
Baroreceptors
Baroreceptors of Carotid
Sinus and Aortic Sinus
Provide information on blood
pressure to cardiovascular and
respiratory control centers
Baroreceptors of Lung
Provide information on lung
stretching to respiratory rhythmicity
centers for control of respiratory rate
Baroreceptors of Digestive Tract
Provide information on volume of
tract segments, trigger reflex
movement of materials along tract
Baroreceptors of Colon
Provide information on volume of
fecal material in colon, trigger
defecation reflex
Baroreceptors of Bladder Wall
Provide information on volume of
urinary bladder, trigger urinary reflex
The General Senses
• Mechanoreceptors
• Proprioceptors
• Monitor the position of joints
• Monitor tension in the tendons and ligaments
• Golgi tendon organs are the receptors in the
tendons
• Monitor the length of muscle fibers upon
contraction
• Muscle spindles are receptors in the muscles
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The General Senses
• Chemoreceptors
• Detect small changes in the concentration of
chemicals
• Respond to water-soluble or lipid-soluble
compounds
• Found in respiratory centers of the:
• Medulla oblongata
• Carotid arteries
• Aortic arch
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Figure 18.5 Chemoreceptors
© 2015 Pearson Education, Inc.
Chemoreceptors
Sensitive to changes in pH
and PCO2in cerebrospinal fluid
Chemoreceptors In and
Near Respiratory Centers
of Medulla Oblongata
Sensitive to changes in pH,
PCO2, and PO2
in blood
Chemoreceptors
of Carotid Bodies
Sensitive to changes in pH,
PCO2, and PO2
in blood
Chemoreceptors
of Aortic Bodies
Via cranial
nerve X
Via cranial
nerve IX
Trigger reflexive
adjustments in
depth and rate of
respiration
Trigger reflexive
adjustments in
respiratory and
cardiovascular
activity
Chemoreceptive neurons Blood vessel
Carotid body LM x 1500
Olfaction (Smell)
• Olfaction
• The olfactory epithelium consists of:
• Olfactory receptors
• Supporting cells
• Basal cells
• Olfactory glands
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Figure 18.6a The Olfactory Organs
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Olfactory
epithelium
Olfactory Pathway
Olfactory
nerve
fibers (N I)
Olfactory
bulb
Olfactory
tract
Central
nervous
system
Cribriform
plate
Superior
nasal
concha
Olfactory
epithelium
The distribution of the olfactory receptors on
the left side of the nasal septum is shown by
the shading.
a
Figure 18.6b The Olfactory Organs
© 2015 Pearson Education, Inc.
Regenerative basal cell;
divides to replace worn-
out olfactory receptor cellsOlfactory
gland
To
olfactory
bulb
Olfactory
nerve fibers
Developing
olfactory
receptor cell
Supporting cell
Mucous layer
Olfactory cilia;
surfaces contain
receptor proteins
Cribriform
plate
Lamina
propria
Olfactory
epithelium
Substance being smelled
A detailed view of the olfactory epithelium.b
Olfactory
receptor cell
Knob
Olfaction (Smell)
• Olfactory Pathways
• Axons leave the olfactory epithelium
• Pass through the cribriform foramina
• Synapse on neurons in the olfactory bulbs
• Impulses travel to the brain via CN I
• Arrive at the cerebral cortex, hypothalamus, and
limbic system
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Figure 18.6a The Olfactory Organs
© 2015 Pearson Education, Inc.
Olfactory
epithelium
Olfactory Pathway
Olfactory
nerve
fibers (N I)
Olfactory
bulb
Olfactory
tract
Central
nervous
system
Cribriform
plate
Superior
nasal
concha
Olfactory
epithelium
The distribution of the olfactory receptors on
the left side of the nasal septum is shown by
the shading.
a
Olfaction (Smell)
• Olfactory Discrimination
• The epithelial receptors have different sensitivities
and we therefore “detect” different smells
• Olfactory receptors can be replaced
• The replacement activity declines with age
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Gustation (Taste)
• Gustation
• The tongue consists of papillae
• Papillae consist of taste buds
• There are three types of papillae
• Filiform
• Fungiform
• Circumvallate
• Taste buds consist of gustatory cells
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Figure 18.7ab Gustatory Reception
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Water receptors
(pharynx) Umami
Sour
Bitter
Salty
Sweet
Taste
buds
Circumvallate papilla
Fungiform papilla
Filiform papillae
Gustatory receptors are
found in taste buds that
form pockets in the
epithelium of the fungiform
and circumvallate papillae.
Papillae on the surface
of the tongue.
a
b
Gustation (Taste)
• Gustatory Receptors
• Taste buds consist of gustatory cells
• Each gustatory cell has a slender microvilli that
extends through the taste pore into the
surrounding fluid
• Dissolved chemicals contact the microvilli
• This provides a stimulus that changes the
transmembrane potential of the gustatory cell
• Information goes to the brain for the interpretation
of taste
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Gustation (Taste)
• Gustatory Pathways
• Dissolved chemicals contact the taste hairs
(microvilli)
• Impulses go from the gustatory cell through CN
VII, IX, and X
• Synapse in the nucleus solitarius of the medulla
oblongata
• Synapse in the medial lemniscus
• Synapse in the thalamus
• Information arrives at the gustatory cortex
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Figure 18.8 Gustatory Pathways
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Gustatory
cortex
Thalamic
nucleus
Medial
lemniscus
Nucleus
solitarius
Vagus nerve
(N X)
Facial nerve
(N VII)
Glossopharyngeal
nerve (N IX)
Gustation (Taste)
• Gustatory Discrimination
• We begin life with more than 10,000 taste buds
• The number declines rapidly by age 50
• Coupled with the decline in olfactory receptors,
taste diminishes as we age
• Threshold level is low for gustatory cells
responsible for unpleasant stimuli
• Threshold level is high for gustatory cells
responsible for pleasant stimuli
© 2015 Pearson Education, Inc.
Gustation (Taste)
• Gustatory Discrimination
• The are four (possibly six) primary tastes
sensations
• Sweet
• Salty
• Sour
• Bitter
• Umami
• Taste that is characteristic of beef and chicken broth
• Water
• Located mainly in the pharynx region
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Equilibrium and Hearing
• Equilibrium and Hearing
• Structures of the ear are involved in balance and
hearing
• The ear is subdivided into three regions
• External ear
• Middle ear
• Inner ear
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Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Equilibrium and Hearing
• The External Ear
• Consists of:
• Auricle (pinna)
• External acoustic meatus
• Tympanic membrane
• Ceruminous glands
• Produces cerumen (earwax)
© 2015 Pearson Education, Inc.
Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Equilibrium and Hearing
• The Middle Ear
• Consists of:
• Tympanic cavity
• Auditory ossicles
• Malleus, incus, and stapes
• Auditory tube (pharyngotympanic tube)
• Muscles:
• Tensor tympani
• Stapedius
© 2015 Pearson Education, Inc.
Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Figure 18.10a The Middle Ear
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Auditory tube
Auditory ossicles
Tympanic membrane
External acoustic
meatus
Tympanic cavity
(middle ear)
Inner ear
Inferior view of the right temporal bone
drawn, as if transparent, to show the
location of the middle and inner ear
a
Figure 18.10b The Middle Ear
© 2015 Pearson Education, Inc.
Stabilizing
ligament
Chorda tympani
nerve (cut), a
branch of N VII
External acoustic
meatus
Tympanic cavity
(middle ear)
Tympanic membrane
(tympanum)
Structures within the middle ear cavity
Temporal bone
(petrous part)
Malleus
Incus
Base of stapes
at oval window
Tensor tympani
muscle
Stapes
Round window
Auditory tube
Stapedius
muscle
b
Figure 18.10c The Middle Ear
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Incus
Malleus
Points of
attachment
to tympanic
membrane
Stapes
Base
of stapes
The isolated auditory ossiclesc
Figure 18.10d The Middle Ear
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The tympanic membrane and auditory ossicles as
seen through a fiber-optic tube inserted along the
auditory canal and into the middle ear cavity
Malleus
Tendon of tensor
tympani muscle
Malleus attached
to tympanic
membrane
Inner surface
of tympanic
membrane
Incus
Base of
stapes at
oval window
Stapes
Stapedius
muscle
d
Equilibrium and Hearing
• The Inner Ear
• Consists of:
• Receptors housed in membranous labyrinth (within
the bony labyrinth)
• Bony labyrinth
• Vestibule
• Semicircular canals
• Cochlea
• Utricle
• Saccule
© 2015 Pearson Education, Inc.
Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Figure 18.12a Semicircular Canals and Ducts
© 2015 Pearson Education, Inc.
Semicircular
canal
Semicircular
ducts
Anterior
Lateral
Posterior VestibuleCristae within ampullae
Maculae
Endolymphatic sac
Membranous
labyrinth
Bony labyrinth
Cochlea
Utricle
Saccule
Vestibular duct
Cochlear duct
Tympanic
ductOrgan of
CortiAnterior view of the bony
labyrinth cut away to show the
semicircular canals and the
enclosed semicircular ducts of
the membranous labyrinth.
a
KEY
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• The vestibular complex is the part of inner ear that
provides equilibrium sensations by detecting
rotation, gravity, and acceleration
• Consists of:
• Semicircular canals
• Utricle
• Saccule
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Figure 18.12a Semicircular Canals and Ducts
© 2015 Pearson Education, Inc.
Semicircular
canal
Semicircular
ducts
Anterior
Lateral
Posterior VestibuleCristae within ampullae
Maculae
Endolymphatic sac
Membranous
labyrinth
Bony labyrinth
Cochlea
Utricle
Saccule
Vestibular duct
Cochlear duct
Tympanic
ductOrgan of
CortiAnterior view of the bony
labyrinth cut away to show the
semicircular canals and the
enclosed semicircular ducts of
the membranous labyrinth.
a
KEY
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• The semicircular canals
• Each semicircular canal encases a duct
• The beginning of each duct is the ampulla
• Within each ampulla is a crista with hair cells
• Each hair cell contains a kinocilium and stereocilia
• These are embedded in gelatinous material called
the cupula
• The movement of the body causes movement of
fluid in the canal, which in turn causes movement
of the cupula and hair cells, which the brain detects
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• When you rotate your head:
• The endolymph in the semicircular canals begins to
move
• This causes the bending of the kinocilium and
stereocilia
• This bending causes depolarization of the
associated sensory nerve
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• When you rotate your head:
• When you rotate your head to the right, the hair
cells are bending to the left (due to movement of
the endolymph)
• When you move in a circle and then stop abruptly,
the endolymph moves back and forth causing the
hair cells to bend back and forth resulting in
confusing signals, thus dizziness
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• The utricle and saccule
• The utricle and saccule are connected to the
ampulla and to each other and to the fluid within
the cochlea
• Hair cells of the utricle and saccule are in clusters
called maculae
• Hair cells are embedded in gelatinous material
consisting of statoconia (calcium carbonate
crystals)
• Gelatinous material and statoconia collectively are
called an otolith
© 2015 Pearson Education, Inc.
Figure 18.14 The Function of the Semicircular Ducts, Part II
© 2015 Pearson Education, Inc.
Anterior semicircular
duct for “yes”
Lateral
semicircular
duct for “no”
Posterior semicircular
duct for “tilting head”
A superior view showing
the planes of sensitivity for
the semicircular ducts
Location and orientation of
the membranous labyrinth
within the petrous parts of
the temporal bones
a b
Figure 18.13a The Function of the Semicircular Ducts, Part I
© 2015 Pearson Education, Inc.
Anterior
Semicircular ducts
Posterior
Lateral
Ampulla
Vestibular branch (N VIII)
Cochlea
Endolymphatic sac
Endolymphatic duct
Maculae
Saccule
Anterior view of the
maculae and semicircular
ducts of the right side.
a
Utricle
Figure 18.13ab The Function of the Semicircular Ducts, Part I
© 2015 Pearson Education, Inc.
Anterior
Semicircular ducts
Posterior
Lateral
Ampulla
Vestibular branch (N VIII)
Cochlea
Endolymphatic sac
Endolymphatic duct
Maculae
Saccule
Anterior view of the
maculae and semicircular
ducts of the right side.
Cupula
Ampulla
filled with
endolymph
Hair cells
Crista
Supporting cells
Sensory nerve
A section through the ampulla of a semicircular duct.
a
b
Utricle
Figure 18.13b The Function of the Semicircular Ducts, Part I
© 2015 Pearson Education, Inc.
Cupula
Ampulla
filled with
endolymph
Hair cells
Crista
Supporting cells
Sensory nerve
A section through the ampulla of a semicircular duct.b
Figure 18.13c The Function of the Semicircular Ducts, Part I
© 2015 Pearson Education, Inc.
Direction of
duct rotation
Direction of
duct rotationDirection of relative
endolymph movement
Semicircular duct
Cupula
At rest
Endolymph movement along the length of the duct
moves the cupula and stimulates the hair cells.
c
Figure 18.13d The Function of the Semicircular Ducts, Part I
© 2015 Pearson Education, Inc.
Displacement in
this direction
stimulates hair cell
Displacement in
this direction
inhibits hair cell
StereociliaKinocilium
Hair cell
Supporting
cell
Sensory
nerve
ending
Structure of a typical hair cell showing details revealed
by electron microscopy. Bending the stereocilia toward
the kinocilium depolarizes the cell and stimulates the
sensory neuron. Displacement in the opposite
direction inhibits the sensory neuron.
d
Equilibrium and Hearing
• The Vestibular Complex and Equilibrium
• When you move up or down (elevator movement):
• Otoliths rest on top of the maculae
• When moving upward, the otoliths press down on
the macular surface
• When moving downward, the otoliths lift off the
macular surface
• When you tilt side to side:
• When tilting to one side, the otoliths shift to one
side of the macular surface
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Figure 18.15a The Maculae of the Vestibule
© 2015 Pearson Education, Inc.
Otolith
Gelatinous
material
Statoconia
Hair cells
Nerve fibers
Detailed structure of a
sensory macula
a
Figure 18.15ab The Maculae of the Vestibule
© 2015 Pearson Education, Inc.
Statoconia
Otolith
Gelatinous
material
Statoconia
Hair cells
Nerve fibers
Otolith
A scanning electron micrograph
showing the crystalline structure
of otoliths
Detailed structure of a
sensory maculaa
b
Figure 18.15c The Maculae of the Vestibule
© 2015 Pearson Education, Inc.
Head in Neutral Position Head Tilted Posteriorly
GravityGravity
Receptor
output
increases
Otolith moves
“downhill,”
distorting hair
cell processes
Diagrammatic view of changes in otolith position during tilting of the headc
1 2
Equilibrium and Hearing
• Pathways for Vestibular Sensations
• Sensory fibers form the vestibular branch of the
vestibulocochlear nerve
• Synapse within the vestibular nuclei
• Located between the pons and medulla oblongata
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Figure 18.16 Neural Pathways for Equilibrium Sensations
© 2015 Pearson Education, Inc.
Semicircular
canalsVestibular
ganglion
Red nucleus
N III
N IV
Vestibular
branch
Vestibule
Cochlear
branch
Vestibulocochlear
nerve (N VIII)
Vestibular
nucleusN VI
N XI
To
cerebellum
To superior colliculus and
relay to cerebral cortex
Vestibulospinal
tracts
Equilibrium and Hearing
• Pathways for Vestibular Sensations
• The vestibular nuclei:
• Integrate sensory information from each side of the
head
• Sends information to:
• Cerebellum
• Cerebral cortex
• Motor nuclei within the brain stem and spinal cord
• Cranial nerves involved are:
• III, IV, VI, and XI
© 2015 Pearson Education, Inc.
Figure 18.16 Neural Pathways for Equilibrium Sensations
© 2015 Pearson Education, Inc.
Semicircular
canalsVestibular
ganglion
Red nucleus
N III
N IV
Vestibular
branch
Vestibule
Cochlear
branch
Vestibulocochlear
nerve (N VIII)
Vestibular
nucleusN VI
N XI
To
cerebellum
To superior colliculus and
relay to cerebral cortex
Vestibulospinal
tracts
Equilibrium and Hearing
• Hearing
• The cochlea:
• Consists of “snail-shaped” spirals
• Spirals coil around a central area called the
modiolus
• Within the modiolus are sensory neurons
• The sensory neurons are associated with CN VIII
• Organ of Corti
© 2015 Pearson Education, Inc.
Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Equilibrium and Hearing
• The Cochlea (continued)
• Each spiral consists of three layers
• Scala vestibuli (vestibular duct): consists of
perilymph
• Scala tympani (tympanic duct): consists of
perilymph
• Scala media (cochlear duct): consists of
endolymph / this layer is between the scala
vestibuli and scala tympani
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• The Cochlea (continued)
• There is a basilar membrane between each layer
• The scala vestibuli and scala tympani are
connected at the apical end of the cochlea
• Sense organs rest on the basilar membrane within
the scala media
© 2015 Pearson Education, Inc.
Figure 18.17a The Cochlea and Organ of Corti
© 2015 Pearson Education, Inc.
Round window
Stapes at
oval window
Cochlear duct
Vestibular duct
Tympanic duct
Cochlear
branch
Vestibular
branch
Vestibulocochlear
nerve (N VIII)
Structure of the
cochlea in partial
section
Semicircular
canals
From oval window
to tip of spiral
From tip of spiral
to round window
KEY
a
Figure 18.17b The Cochlea and Organ of Corti
© 2015 Pearson Education, Inc.
Apical turn
Vestibular
membrane
Tectorial membrane
Basilar membrane
Middle turn
Vestibular duct (scala
vestibuli—contains perilymph)
Organ of Corti
Cochlear duct (scala
media—contains endolymph)
Basal turn
Tympanic duct (scala
tympani—contains perilymph)
Temporal bone (petrous part)
Cochlear branchVestibulocochlear
nerve (N VIII)
To round
window
From
oval
window
Modiolus
Spiral
ganglion
Structure of the cochlea within the temporal
bone showing the turns of the vestibular duct,
cochlear duct, and tympanic duct
b
Equilibrium and Hearing
• The Cochlea
• The Organ of Corti
• Also known as the spiral organ
• Rests on the basilar membrane between the scala
media and the scala tympani
• Hair cells are in contact with an overlying tectorial
membrane
• This membrane is attached to the lining of the scala
media
• Sound waves ultimately cause a distortion of the
tectorial membrane, thus stimulating the organ of
Corti
© 2015 Pearson Education, Inc.
Figure 18.17b The Cochlea and Organ of Corti
© 2015 Pearson Education, Inc.
Apical turn
Vestibular
membrane
Tectorial membrane
Basilar membrane
Middle turn
Vestibular duct (scala
vestibuli—contains perilymph)
Organ of Corti
Cochlear duct (scala
media—contains endolymph)
Basal turn
Tympanic duct (scala
tympani—contains perilymph)
Temporal bone (petrous part)
Cochlear branchVestibulocochlear
nerve (N VIII)
To round
window
From
oval
window
Modiolus
Spiral
ganglion
Structure of the cochlea within the temporal
bone showing the turns of the vestibular duct,
cochlear duct, and tympanic duct
b
Figure 18.17d The Cochlea and Organ of Corti
© 2015 Pearson Education, Inc.
Bony cochlear wall
Vestibular duct
Vestibular membrane
Cochlear duct
Tectorial membrane
Basilar membrane
Tympanic duct
Organ of Corti
Spiral
ganglion
Cochlear branch
of N VIIIThree-dimensional section showing the
detail of the cochlear chambers, tectorial
membrane, and organ of Corti
d
Figure 18.17e The Cochlea and Organ of Corti
© 2015 Pearson Education, Inc.
Tectorial membrane
Outer
hair cell
Basilar membrane Inner hair cell Nerve fibers
Diagrammatic and histological sections through the
receptor hair cell complex of the organ of Corti
Cochlear duct (scala media)
Vestibular membrane
Tectorial membrane
Tympanic duct
(scala tympani)Basilar
membrane
Hair cells
of organ
of Corti
Spiral ganglion
cells of
cochlear nerve
Organ of Corti LM x 125e
Equilibrium and Hearing
• Sound Detection
• Sound waves enter the external acoustic meatus
• The tympanic membrane vibrates
• Causes the vibration of the ossicles
• The stapes vibrates against the oval window of the
scala tympani
• Perilymph begins to move
© 2015 Pearson Education, Inc.
Figure 18.9 Anatomy of the Ear
© 2015 Pearson Education, Inc.
External Ear Middle Ear Inner Ear
Elastic
cartilages
Auricle
Auditory ossicles
Oval
windowSemicircular canals
Petrous part of
temporal bone
Facial nerve (N VII)
Vestibulocochlear
nerve (N VIII)
Bony labyrinth
of inner ear
Cochlea
Tympanic
cavity
External acoustic
meatus
Tympanic
membrane
Round
window
Vestibule
Auditory tube
To
nasopharynx
Equilibrium and Hearing
• Sound Detection
• As the perilymph moves:
• Pressure is put on the scala media
• This pressure distorts the hair cells of the organ of
Corti
• This distortion depolarizes the neurons
• Nerve signals are sent to the brain via CN VIII
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• Auditory Pathways
• Stimulation of hair cells in the cochlea
• Sensory neurons carry the sound information from
N VIII to the cochlear nuclei
• Information travels to the inferior colliculi of the
midbrain
© 2015 Pearson Education, Inc.
Equilibrium and Hearing
• Auditory Pathways (continued)
• The inferior colliculi causes the rotation of the
head in the direction of the sound
• Information goes to the medial geniculate nucleus
• Information goes to the auditory cortex of the
temporal lobe
© 2015 Pearson Education, Inc.
Figure 18.18 Pathways for Auditory Sensations
© 2015 Pearson Education, Inc.
Stimulation of hair cells at a specific
location along the basilar membrane
activates sensory neurons.
Projection fibers then deliver the
information to specific locations within
the auditory cortex of the temporal lobe.
Ascending acoustic information goes
to the medial geniculate nucleus.
The inferior colliculi direct a variety of
unconscious motor responses to sounds.
To ipsilateral
auditory
cortex
Cochlea
Low-frequency
sounds
High-frequency
sounds
Vestibular
branch
To reticular formation and
motor nuclei of cranial nerves
Superior olivary nucleus
Vestibulocochlear
nerve (N VIII)
Cochlear nucleus
Sensory neurons carry the sound
information in the cochlear branch
of the vestibulocochlear nerve
(N VIII) to the cochlear nuclei.
Information ascends from the cochlear
nuclei to the inferior colliculi of the midbrain.
Motor output to spinal cord
through the tectospinal tracts
First-order neuron
Second-order neuron
Third-order neuron
Fourth-order neuron
3
5
2
1
KEY
4
6
Low-frequency
sounds
High-
frequency
sounds
Thalamus
Vision
• Accessory Structures of the Eye
• Palpebrae (eyelids)
• Medial and lateral canthus
• Connect the eyelids at the corners of the eye
• Palpebral fissure
• Area between the eyelid
• Eyelashes
• Contain root hair plexus, which triggers the blinking
reflex
© 2015 Pearson Education, Inc.
Vision
• Accessory Structures of the Eye (continued)
• Conjunctiva
• Epithelial lining of the eyelid
• Glands
• Glands of Zeis, tarsal glands, lacrimal gland,
lacrimal caruncle
© 2015 Pearson Education, Inc.
Figure 18.19a Accessory Structures of the Eye, Part I
© 2015 Pearson Education, Inc.
Eyelashes
Palpebra
Palpebral
fissure
Medial
canthus
Lacrimal
caruncle
Lateral
canthus
Sclera
Corneal
limbus
Pupil
Superficial anatomy of the right eye and its accessory structuresa
Figure 18.19b Accessory Structures of the Eye, Part I
© 2015 Pearson Education, Inc.
Lacrimal gland
(orbital portion)
Tarsal plates
Tendon of superior
oblique muscle
Levator palpebrae
superioris muscle
Orbital fat
Palpebral fissure
Lacrimal sac
Orbicularis
oculi (cut)
Diagrammatic representation of a superficial dissection of the right orbitb
Figure 18.19c Accessory Structures of the Eye, Part I
© 2015 Pearson Education, Inc.
Tendon of superior
oblique muscle
Lacrimal punctum
Superior lacrimal
canaliculus
Medial canthus
Inferior lacrimal
canaliculus
Lacrimal sac
Nasolacrimal duct
Inferior nasal
concha
Opening of
nasolacrimal duct
Superior
rectus muscle
Lacrimal
gland ducts
Lacrimal gland
Lateral canthus
Lower eyelid
Inferior
rectus muscle
Inferior
oblique muscle
Diagrammatic representation of a deeper dissection of the right eye
showing its position within the orbit and its relationship to accessory
structures, especially the lacrimal apparatus
c
Vision
• Accessory Structures of the Eye
• Eyelids
• Also known as palpebrae
• Connected at the corners called medial and lateral
canthus
• Eyelashes are along the palpebral borders
• Eyelashes are associated with sebaceous glands
• Tarsal glands are located along the inner lining of
the eyelids
• They secrete lipid products that prevent the eyelids
from sticking together
© 2015 Pearson Education, Inc.
Vision
• Accessory Structures of the Eye
• Eyelids
• Conjunctiva
• Covers the inside lining of the eyelids and the
outside lining of the eye
• Fluid production helps prevent these layers from
becoming dry
• Palpebral conjunctiva (Inner lining of the eyelids)
• Ocular conjunctiva (Outer lining of the eyelids)
© 2015 Pearson Education, Inc.
Figure 18.19a Accessory Structures of the Eye, Part I
© 2015 Pearson Education, Inc.
Eyelashes
Palpebra
Palpebral
fissure
Medial
canthus
Lacrimal
caruncle
Lateral
canthus
Sclera
Corneal
limbus
Pupil
Superficial anatomy of the right eye and its accessory structuresa
Vision
• Accessory Structures of the Eye
• Eyelids
• All of the glands are for protection or lubrication
• Glands of Zeis: sebaceous glands / associated
with eyelashes
• Tarsal glands: secrete a lipid-rich product / keeps
the eyelids from sticking together / located along
the inner margin of the eyelids
• Lacrimal glands: produce tears / located at the
superior, lateral portion of the eye
• Lacrimal caruncle glands: produce thick
secretions / located within the canthus areas
© 2015 Pearson Education, Inc.
Vision
• Accessory Structures of the Eye
• Eyelids
• An infection of the tarsal gland may result in a cyst
• An infection of any of the other glands may result in
a sty
© 2015 Pearson Education, Inc.
Vision
• Accessory Structures of the Eye
• The Lacrimal Apparatus
• Produces, distributes, and removes tears
• The lacrimal apparatus consists of:
• Lacrimal glands (produce tears)
• Lacrimal canaliculi
• Lacrimal sac
• Nasolacrimal duct
© 2015 Pearson Education, Inc.
Figure 18.19c Accessory Structures of the Eye, Part I
© 2015 Pearson Education, Inc.
Tendon of superior
oblique muscle
Lacrimal punctum
Superior lacrimal
canaliculus
Medial canthus
Inferior lacrimal
canaliculus
Lacrimal sac
Nasolacrimal duct
Inferior nasal
concha
Opening of
nasolacrimal duct
Superior
rectus muscle
Lacrimal
gland ducts
Lacrimal gland
Lateral canthus
Lower eyelid
Inferior
rectus muscle
Inferior
oblique muscle
Diagrammatic representation of a deeper dissection of the right eye
showing its position within the orbit and its relationship to accessory
structures, especially the lacrimal apparatus
c
Vision
• Accessory Structures of the Eye
• The Lacrimal Apparatus
• Tears are produced by the lacrimal glands
• Flow over the ocular surface
• Flow into the nasolacrimal canal (foramen)
• This foramen enters into the nasal cavity
• Therefore, when you sob heavily, tears flow across
your eye and down your face and also through the
nasolacrimal canal into your nose and out, resulting
in a “runny” nose
© 2015 Pearson Education, Inc.
Vision
• The Eye
• Consist of:
• Sclera
• Cornea
• Pupil
• Iris
• Lens
• Anterior cavity
• Posterior cavity
• Three tunics:
• (1) fibrous tunic, (2) vascular tunic, and
(3) neural tunic
• Retina
© 2015 Pearson Education, Inc.
Figure 18.21b Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Posterior cavity
(Vitreous chamber filled
with the vitreous body)
Ora serrata Fornix
Palpebral conjunctiva
Ocular conjunctiva
Ciliary body
Anterior chamber
(filled with aqueous
humor)
Lens
Pupil
Cornea
Iris
Posterior chamber
(filled with aqueous
humor)
Corneal limbus
Suspensory
ligaments
Fovea
Central retinal
artery and vein
Optic nerve (N II)
Optic disc
Retina
Choroid
Sclera
Major anatomical landmarks and features
in a diagrammatic view of the left eyeb
Figure 18.21ab Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Fibrous
tunic
(sclera)
Vascular
tunic
(choroid)
Neural
tunic
(retina) Posterior cavity
(Vitreous chamber filled
with the vitreous body)
Ora serrata Fornix
Palpebral conjunctiva
Ocular conjunctiva
Ciliary body
Anterior chamber
(filled with aqueous
humor)
Lens
Pupil
Cornea
Iris
Posterior chamber
(filled with aqueous
humor)
Corneal limbus
Suspensory
ligaments
Fovea
Central retinal
artery and vein
Optic nerve (N II)
Optic disc
Retina
Choroid
Sclera
Major anatomical landmarks and features
in a diagrammatic view of the left eye
The three layers, or
tunics, of the eye
a
b
Vision
• The Eyes
• The Fibrous Tunic (outermost layer)
• Makes up the sclera and cornea
• The cornea is modified sclera
• Provides some degree of protection
• Provides attachment sites for extra-ocular muscles
• Contains structures associated with focusing
© 2015 Pearson Education, Inc.
Figure 18.22 The Lens and Chambers of the Eye
© 2015 Pearson Education, Inc.
Ciliary
body
Ciliary
processes
Posterior
cavity
Suspensory
ligaments
Sclera
Canal of Schlemm
Anterior chamber
Posterior chamber
Anterior cavity
Pupil
Iris
Pupillary sphincter
muscle
Pupillary dilator muscle
Cornea
Ciliary
muscle
Vascular tunic
Choroid
Ciliary body
Iris
Anterior cavity
Fibrous tunic
Cornea
Sclera
Posterior
cavity
Neural tunic
(retina)Neural layer
Pigmented layer
Its position is maintained by the suspensory
ligaments that attach the lens to the ciliary body.
The lens is suspended between the posterior cavity
and the posterior chamber of the anterior cavity.
a b
Lens
Vision
• The Eyes
• The Vascular Tunic (middle layer)
• Consists of blood vessels, lymphatics, and intrinsic
eye muscles
• Regulates the amount of light entering the eye
• Secretes and reabsorbs aqueous fluid (aqueous
humor)
• Controls the shape of the lens
• Includes the iris, ciliary body, and the choroid
© 2015 Pearson Education, Inc.
Figure 18.22 The Lens and Chambers of the Eye
© 2015 Pearson Education, Inc.
Ciliary
body
Ciliary
processes
Posterior
cavity
Suspensory
ligaments
Sclera
Canal of Schlemm
Anterior chamber
Posterior chamber
Anterior cavity
Pupil
Iris
Pupillary sphincter
muscle
Pupillary dilator muscle
Cornea
Ciliary
muscle
Vascular tunic
Choroid
Ciliary body
Iris
Anterior cavity
Fibrous tunic
Cornea
Sclera
Posterior
cavity
Neural tunic
(retina)Neural layer
Pigmented layer
Its position is maintained by the suspensory
ligaments that attach the lens to the ciliary body.
The lens is suspended between the posterior cavity
and the posterior chamber of the anterior cavity.
a b
Lens
Vision
• The Eyes
• The Vascular Tunic
• The iris
• Consists of blood vessels, pigment, and smooth
muscles
• The pigment creates the color of the eye
• The smooth muscles contract to change the
diameter of the pupil
© 2015 Pearson Education, Inc.
Vision
• The Eyes
• The Vascular Tunic
• The ciliary body
• The ciliary bodies consist of ciliary muscles
connected to suspensory ligaments, which are
connected to the lens
• The choroid
• Highly vascularized
• The innermost portion of the choroid attaches to the
outermost portion of the retina
© 2015 Pearson Education, Inc.
Vision
• The Eyes
• The Neural Tunic (inner layer)
• Also called the retina
• Made of two layers
• Pigmented layer—outer layer
• Neural layer—inner layer
• Retina cells
• Rods (night vision)
• Cones (color vision)
© 2015 Pearson Education, Inc.
Figure 18.22 The Lens and Chambers of the Eye
© 2015 Pearson Education, Inc.
Ciliary
body
Ciliary
processes
Posterior
cavity
Suspensory
ligaments
Sclera
Canal of Schlemm
Anterior chamber
Posterior chamber
Anterior cavity
Pupil
Iris
Pupillary sphincter
muscle
Pupillary dilator muscle
Cornea
Ciliary
muscle
Vascular tunic
Choroid
Ciliary body
Iris
Anterior cavity
Fibrous tunic
Cornea
Sclera
Posterior
cavity
Neural tunic
(retina)Neural layer
Pigmented layer
Its position is maintained by the suspensory
ligaments that attach the lens to the ciliary body.
The lens is suspended between the posterior cavity
and the posterior chamber of the anterior cavity.
a b
Lens
Figure 18.23a Retinal Organization
© 2015 Pearson Education, Inc.
Horizontal cell Cone Rod
Amacrine cell
Choroid
Pigmented
layer of retina
Rods and
cones
Bipolar cells
Ganglion cells
Nuclei of
ganglion cells
Nuclei of rods
and cones
Nuclei of
bipolar cells
The retina LM x 75
LIGHTHistological organization of the retina. Note that the photoreceptors are
located closest to the choroid rather than near the vitreous chamber.
a
Figure 18.23b Retinal Organization
© 2015 Pearson Education, Inc.
PIGMENT
EPITHELIUM
Melanin
granules
OUTER SEGMENT
Visual pigments in
membrane discs
Discs
Connecting
stalks
Mitochondria
Golgi
apparatus
Nuclei
Cone Rods
INNER SEGMENT
Location of major
organelles and
metabolic operations
such as photopigment
synthesis and
ATP production
Synapses with
bipolar cells
Diagrammatic view of the fine
structure of rods and cones, based
on data from electron microscopy.
Bipolar cell
LIGHTb
Vision
• The Eyes
• The Neural Tunic (inner layer)
• Retinal organization
• There are rods and cones all over the retina
• 100% cones in the fovea centralis area
• The best color vision is when an object is focused
on the fovea centralis
• 0% rods or cones in the optic disc area
• If an object is focused on this area, vision does not
occur
• Also known as the “blind spot”
© 2015 Pearson Education, Inc.
Vision
• The Chambers of the Eye
• Anterior cavity
• Anterior chamber
• Posterior chamber
• Filled with fluid called aqueous humor
• Posterior cavity
• Vitreous chamber
• Filled with fluid called vitreous body
© 2015 Pearson Education, Inc.
Figure 18.21a-d Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Fibrous
tunic
(sclera)
Vascular
tunic
(choroid)
Neural
tunic
(retina) Posterior cavity
(Vitreous chamber filled
with the vitreous body)
Ora serrata Fornix
Palpebral conjunctiva
Ocular conjunctiva
Ciliary body
Anterior chamber
(filled with aqueous
humor)
Lens
Pupil
Cornea
Iris
Posterior chamber
(filled with aqueous
humor)
Corneal limbus
Suspensory
ligaments
Fovea
Central retinal
artery and vein
Optic nerve (N II)
Optic disc
Retina
Choroid
Sclera
Major anatomical landmarks and features
in a diagrammatic view of the left eye
The three layers, or
tunics, of the eyea
b
Optic nerve
(N II)
Dura
mater
Retina Choroid Sclera
Ora serrata
Conjunctiva
Cornea
Lens
Anterior chamber
Iris
Posterior chamber
Suspensory
ligaments
Ciliary body
Pupillary
dilator muscles
(radial)
Constrictors
contract
Pupillary
constrictor
muscles
(sphincter)
Dilators contract
The action of pupillary muscles
and changes in pupillary diameter Sagittal section through the eye
Posterior
cavity
(vitreous
chamber)
c
d
Pupil
Vision
• The Chambers of the Eye
• Aqueous humor
• Secreted by cells at the ciliary body area
• Enters the posterior chamber (posterior of the iris)
• Flows through the pupil area
• Enters the anterior chamber
• Flows through the canal of Schlemm
• Enters into venous circulation
© 2015 Pearson Education, Inc.
Figure 18.24 The Circulation of Aqueous Humor
© 2015 Pearson Education, Inc.
Cornea
Pupil
Lens
Posterior cavity
(vitreous chamber)
Anterior chamber
Posterior chamber
Ciliary process
Suspensory
ligaments
Pigmented
epithelium
Anterior
cavity
Canal of Schlemm
Body of iris
Conjunctiva
Ciliary body
Sclera
Choroid
Retina
Vision
• The Chambers of the Eye
• Vitreous body
• Gelatinous material in the posterior chamber
• Supports the shape of the eye
• Supports the position of the lens
• Supports the position of the retina
• Aqueous humor can flow across the vitreous body
and over the retina
© 2015 Pearson Education, Inc.
Figure 18.21d Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Optic nerve
(N II)
Dura
mater
Retina Choroid Sclera
Ora serrata
Conjunctiva
Cornea
Anterior chamber
Posterior chamber
Suspensory
ligaments
Ciliary body
Sagittal section through the eye
Posterior
cavity
(vitreous
chamber)
d
Lens
Iris
Vision
• Aqueous Humor
• If this fluid cannot drain through the canal of
Schlemm, pressure builds up
• This is glaucoma
• Vitreous Body
• If this fluid is not of the right consistency, the
pressure is reduced against the retina
• The retina may detach from the posterior wall
(detached retina)
© 2015 Pearson Education, Inc.
Vision
• The Lens
• Focuses the image on the photoreceptors of the
retina
• Consists of concentric layers of cells
• Changes shape due to:
• Tension in suspensory ligaments
• Contraction and relaxation of ciliary muscles
© 2015 Pearson Education, Inc.
Figure 18.21b Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Posterior cavity
(Vitreous chamber filled
with the vitreous body)
Ora serrata Fornix
Palpebral conjunctiva
Ocular conjunctiva
Ciliary body
Anterior chamber
(filled with aqueous
humor)
Lens
Pupil
Cornea
Iris
Posterior chamber
(filled with aqueous
humor)
Corneal limbus
Suspensory
ligaments
Fovea
Central retinal
artery and vein
Optic nerve (N II)
Optic disc
Retina
Choroid
Sclera
Major anatomical landmarks and features
in a diagrammatic view of the left eyeb
Figure 18.24 The Circulation of Aqueous Humor
© 2015 Pearson Education, Inc.
Cornea
Pupil
Lens
Posterior cavity
(vitreous chamber)
Anterior chamber
Posterior chamber
Ciliary process
Suspensory
ligaments
Pigmented
epithelium
Anterior
cavity
Canal of Schlemm
Body of iris
Conjunctiva
Ciliary body
Sclera
Choroid
Retina
Vision
• Visual Pathways
• Light waves pass through the cornea
• Pass through the anterior chamber
• Pass through the pupil
• Pass through the posterior chamber
• Pass through the lens
• The lens focuses the image on some part of the
retina
• This creates a depolarization of the neural cells
• Signal is transmitted to the brain via CN II
© 2015 Pearson Education, Inc.
Figure 18.21e Sectional Anatomy of the Eye
© 2015 Pearson Education, Inc.
Visual axis
Edge of
pupil
Cornea
Iris
Suspensory ligament of lens
Corneal limbus
Conjunctiva
Lower eyelid
Lateral canthus
Sclera
Choroid
Retina
Posterior cavity
Lateral rectus muscle
Anterior cavity
Posterior
chamber
Anterior
chamber
Lens
Nose
Lacrimal punctum
Lacrimal caruncle
Medial canthus
Ciliary
processes
Ciliary body
Ora serrata
Fovea
Ethmoidal
labyrinth
Medial rectus
muscle
Optic disc
Optic nerve (N II)
Central artery
and vein
Section through the eyee
Orbital fat
Vision
• Visual Pathways
• The retina (continued)
• The cones require light to be stimulated (that’s why
we see color)
• At night (still has to be at least a small amount of
light), the cones deactivate and the rods begin to
be activated (that’s why we can see at night but we
can’t determine color at night)
© 2015 Pearson Education, Inc.
Vision
• Visual Pathways
• Cortical Integration
• Information arrives at the visual cortex of the
occipital lobes
• There is a crossover of information at the optic
chiasm region
© 2015 Pearson Education, Inc.
Figure 18.26 Anatomy of the Visual Pathways, Part II
© 2015 Pearson Education, Inc.
LEFT SIDE RIGHT SIDE
Left eye
onlyBinocular vision Right eye
only
Optic nerve (N II)
Optic chiasm
Optic tractOther hypothalamic
nuclei, pineal gland,
and reticular
formation
Suprachiasmatic
nucleus
Lateral
geniculate
nucleus
Lateral
geniculate
nucleus
Projection
fibers (optic
radiation)
Superior
colliculus
RIGHT CEREBRAL
HEMISPHERE
LEFT CEREBRAL
HEMISPHERE
Visual cortex of
cerebral hemispheres