chapter 18 218/martini ppt... · introduction •sensory information arrives at the cns...

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


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


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


Receptors

• Each receptor has a characteristic sensitivity

• This leads to receptor specificity

• Specificity is due to the structure of the receptor


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


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


Figure 18.1 Receptors and Receptive Fields


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


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)


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


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


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


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


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


Figure 18.2 Referred Pain


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


The General Senses


• Receptors that are sensitive to stretch,

compression, twisting, or distortion of the

plasmalemmae

• There are three types

• Tactile receptors

• Baroreceptors

• Proprioceptors


The General Senses


• 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


The General Senses


• 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


Figure 18.3a Tactile Receptors in the Skin


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




corpuscle

Free nerve

ending

Ruffini corpuscle


Root hair plexus

Sensory

nerves

Merkel cells

Tactile disc

Merkel cells and

tactile discs.b

Figure 18.3c Tactile Receptors in the Skin




corpuscle

Free nerve

ending

Ruffini corpuscle


Root hair plexus

Sensory

nerves

Free nerve endings

of root hair plexus.

c

The General Senses


• 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


Figure 18.3d Tactile Receptors in the Skin




corpuscle

Free nerve

ending

Ruffini 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



tactile discs

Tactile

corpuscleFree nerve

ending

Ruffini corpuscle


Root hair plexus

Sensory

nerves

Capsule

Dendrites

Collagen

fibers

Sensory

nerve fiber

Ruffini corpuscle.e

Figure 18.3f Tactile Receptors in the Skin




corpuscle

Free nerve

ending

Ruffini corpuscle


Root hair plexus

Sensory

nerves

Dermis

Dendritic process

Accessory cells

(specialized fibrocytes)

Concentric layers (lamellae)

of collagen fibers

separated by fluid


Concentric layers

(lamellae) of

collagen fibers

separated by fluid

Dendritic

process

Lamellated corpuscle.

LM x 125

f

The General Senses


• Baroreceptors

• Stretch receptors that monitor changes in the

stretch of organs

• Location:

• Stomach

• Small intestine

• Urinary bladder

• Carotid artery

• Lungs

• Large intestine


Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions


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


fecal material in colon, trigger

defecation reflex

Baroreceptors of Bladder Wall


urinary bladder, trigger urinary reflex

The General Senses


• 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


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


Figure 18.5 Chemoreceptors


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


Figure 18.6a The Olfactory Organs


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


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


Figure 18.6a The Olfactory Organs


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


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


Figure 18.7ab Gustatory Reception


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


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


Figure 18.8 Gustatory Pathways


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


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


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


Figure 18.9 Anatomy of the Ear


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


• The External Ear

• Consists of:

• Auricle (pinna)

• External acoustic meatus

• Tympanic membrane

• Ceruminous glands

• Produces cerumen (earwax)





Elastic

cartilages

Auricle

Auditory ossicles

Oval


Petrous part of

temporal bone


Vestibulocochlear

nerve (N VIII)

Bony labyrinth

of inner ear

Cochlea

Tympanic

cavity

External acoustic

meatus

Tympanic

membrane

Round

window

Vestibule

Auditory tube

To

nasopharynx


• The Middle Ear

• Consists of:

• Tympanic cavity

• Auditory ossicles

• Malleus, incus, and stapes

• Auditory tube (pharyngotympanic tube)

• Muscles:

• Tensor tympani

• Stapedius





Elastic

cartilages

Auricle

Auditory ossicles

Oval


Petrous part of

temporal bone


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


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


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


Incus

Malleus

Points of

attachment

to tympanic

membrane

Stapes

Base

of stapes

The isolated auditory ossiclesc

Figure 18.10d The Middle Ear


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


• The Inner Ear

• Consists of:

• Receptors housed in membranous labyrinth (within

the bony labyrinth)

• Bony labyrinth

• Vestibule

• Semicircular canals

• Cochlea

• Utricle

• Saccule





Elastic

cartilages

Auricle

Auditory ossicles

Oval


Petrous part of

temporal bone


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


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


• 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


Figure 18.12a Semicircular Canals and Ducts


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



• 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




• 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




• 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




• 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


Figure 18.14 The Function of the Semicircular Ducts, Part II


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


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


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


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


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


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



• 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


Figure 18.15a The Maculae of the Vestibule


Otolith

Gelatinous

material

Statoconia

Hair cells

Nerve fibers

Detailed structure of a

sensory macula

a

Figure 18.15ab The Maculae of the Vestibule


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


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


• 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


Figure 18.16 Neural Pathways for Equilibrium Sensations


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


• 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


Figure 18.16 Neural Pathways for Equilibrium Sensations


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


• 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





Elastic

cartilages

Auricle

Auditory ossicles

Oval


Petrous part of

temporal bone


Vestibulocochlear

nerve (N VIII)

Bony labyrinth

of inner ear

Cochlea

Tympanic

cavity

External acoustic

meatus

Tympanic

membrane

Round

window

Vestibule

Auditory tube

To

nasopharynx


• 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



• 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


Figure 18.17a The Cochlea and Organ of Corti


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


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


• 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


Figure 18.17b The Cochlea and Organ of Corti


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


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


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


• 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





Elastic

cartilages

Auricle

Auditory ossicles

Oval


Petrous part of

temporal bone


Vestibulocochlear

nerve (N VIII)

Bony labyrinth

of inner ear

Cochlea

Tympanic

cavity

External acoustic

meatus

Tympanic

membrane

Round

window

Vestibule

Auditory tube

To

nasopharynx


• 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



• 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



• 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


Figure 18.18 Pathways for Auditory Sensations


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


Vision

• Accessory Structures of the Eye (continued)

• Conjunctiva

• Epithelial lining of the eyelid

• Glands

• Glands of Zeis, tarsal glands, lacrimal gland,

lacrimal caruncle


Figure 18.19a Accessory Structures of the Eye, Part I


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


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


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


• 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


Vision


• 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)


Figure 18.19a Accessory Structures of the Eye, Part I


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


• 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


Vision


• 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


Vision


• The Lacrimal Apparatus

• Produces, distributes, and removes tears

• The lacrimal apparatus consists of:

• Lacrimal glands (produce tears)

• Lacrimal canaliculi

• Lacrimal sac

• Nasolacrimal duct


Figure 18.19c Accessory Structures of the Eye, Part I


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


• 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


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


Figure 18.21b Sectional Anatomy of the Eye


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


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


Fibrous

tunic

(sclera)

Vascular

tunic

(choroid)

Neural

tunic

(retina) Posterior cavity



Ora serrata Fornix


Ocular conjunctiva

Ciliary body

Anterior chamber


humor)

Lens

Pupil

Cornea

Iris

Posterior chamber


humor)

Corneal limbus

Suspensory

ligaments

Fovea

Central retinal

artery and vein

Optic nerve (N II)

Optic disc

Retina

Choroid

Sclera


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


Figure 18.22 The Lens and Chambers of the Eye


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




Ciliary

body

Ciliary

processes

Posterior

cavity

Suspensory

ligaments

Sclera

Canal of Schlemm

Anterior chamber

Posterior chamber

Anterior cavity

Pupil

Iris

Pupillary sphincter

muscle


Cornea

Ciliary

muscle

Vascular tunic

Choroid

Ciliary body

Iris

Anterior cavity

Fibrous tunic

Cornea

Sclera

Posterior

cavity

Neural tunic


Pigmented layer





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


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


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)




Ciliary

body

Ciliary

processes

Posterior

cavity

Suspensory

ligaments

Sclera

Canal of Schlemm

Anterior chamber

Posterior chamber

Anterior cavity

Pupil

Iris

Pupillary sphincter

muscle


Cornea

Ciliary

muscle

Vascular tunic

Choroid

Ciliary body

Iris

Anterior cavity

Fibrous tunic

Cornea

Sclera

Posterior

cavity

Neural tunic


Pigmented layer





a b

Lens

Figure 18.23a Retinal Organization


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


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”


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


Figure 18.21a-d Sectional Anatomy of the Eye


Fibrous

tunic

(sclera)

Vascular

tunic

(choroid)

Neural

tunic

(retina) Posterior cavity



Ora serrata Fornix


Ocular conjunctiva

Ciliary body

Anterior chamber


humor)

Lens

Pupil

Cornea

Iris

Posterior chamber


humor)

Corneal limbus

Suspensory

ligaments

Fovea

Central retinal

artery and vein

Optic nerve (N II)

Optic disc

Retina

Choroid

Sclera


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


• 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


Figure 18.24 The Circulation of Aqueous Humor


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


• 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


Figure 18.21d Sectional Anatomy of the Eye


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)


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


Figure 18.21b Sectional Anatomy of the Eye


Posterior cavity



Ora serrata Fornix


Ocular conjunctiva

Ciliary body

Anterior chamber


humor)

Lens

Pupil

Cornea

Iris

Posterior chamber


humor)

Corneal limbus

Suspensory

ligaments

Fovea

Central retinal

artery and vein

Optic nerve (N II)

Optic disc

Retina

Choroid

Sclera


in a diagrammatic view of the left eyeb

Figure 18.24 The Circulation of Aqueous Humor


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


Figure 18.21e Sectional Anatomy of the Eye


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)


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


Figure 18.26 Anatomy of the Visual Pathways, Part II


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

chapter 18 218/martini ppt... · introduction •sensory information arrives at the cns...

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