Figure 17-5b The Sectional Anatomy of the Eye. - PowerPoint Presentation

Slide1

Figure 17-5b The Sectional Anatomy of the Eye.

Posterior

cavity

Iris

Ciliary

body

Choroid

Cornea

Sclera

Neural part

Pigmented part

Anterior

cavity

Fibrous

layer

Vascular layer

(uvea)

Inner layer

(retina)

Horizontal section of right eye

bSlide2

Figure 17-5a The Sectional Anatomy of the Eye.

Fovea

Retina

Choroid

Sclera

Sagittal section of left eye

Corneal

limbus

Iris

Pupil

Cornea

Ora

serrata

Ocular conjunctiva

Eyelash

Lens

Fornix

Palpebral conjunctiva

Optic

nerve

aSlide3

Figure 17-6 The Pupillary Muscles.

Pupillary constrictor

(sphincter)

Pupil

Pupillary dilator

(radial)

The

pupillary dilator

muscles

extend radially

away from the edge of the pupil.

Contraction of these muscles

enlarges the pupil.

The pupillary constrictormuscles form a series ofconcentric circles around thepupil. When these sphinctermuscles contract, the diameterof the pupil decreases.

Increased light intensityIncreased parasympathetic stimulation

Decreased light intensity

Increased sympathetic stimulationSlide4

Figure 17-7a The Organization of the Retina (Part 1 of 2).

Amacrine

cell

Horizontal cell

Cone

Rod

Pigmented

part of retina

Rods and

cones

Bipolar cells

Ganglion cells

LIGHT

The cellular organization of the retina. The photoreceptors are closest to the choroid, rather than near the posterior cavity (vitreous chamber).

aSlide5

Figure 17-7b The Organization of the Retina.

The optic disc in diagrammatic sagittal section.

Optic disc

Neural part

of retina

Pigmented

part of retina

Central retinal vein

Central retinal artery

Optic nerve

Sclera

Choroid

bSlide6

17-3 The EyeHorizontal and

Amacrine Cells Facilitate or inhibit communication between photoreceptors and ganglion cellsAlter sensitivity of retinaOptic DiscCircular region just medial to foveaOrigin of optic nerveBlind spotSlide7

17-3 The EyeThe

LensLens fibersCells in interior of lensNo nuclei or organellesFilled with crystallins, which provide clarity and focusing power to lensCataractCondition in which lens has lost its transparencySlide8

17-3 The EyeLight

RefractionBending of light by cornea and lens Focal pointSpecific point of intersection on retinaFocal distanceDistance between center of lens and focal pointSlide9

Figure 17-10 Factors Affecting Focal Distance.

Focal distance

Close

source

Focal distance

Focal

point

Lens

Light

from

distant

source

(object)

Focal distance

The closer the light source,

the longer the focal distance

The rounder the lens,

the shorter the focal distance

b

c

aSlide10

17-3 The EyeLight Refraction of Lens

AccommodationShape of lens changes to focus image on retina AstigmatismCondition where light passing through cornea and lens is not refracted properly Visual image is distortedSlide11

Figure 17-11 Accommodation.

a

b

Lens rounded

For Distant Vision:

Ciliary

Muscle Relaxed, Lens Flattened

For Close Vision:

Ciliary

Muscle Contracted, Lens Rounded

Ciliary

muscle

contracted

Focal point

on fovea

Lens flattened

Ciliary

muscle

relaxedSlide12

17-3 The EyeLight Refraction of Lens

Image reversalVisual acuityClarity of vision“Normal” rating is 20/20Slide13

Figure 17-12a Image Formation.

a

Light from a point at the top

of an object is focused on

the lower retinal surface.Slide14

Figure 17-12b Image Formation.

b

Light from a point at the

bottom of an object is focused on the upper

retinal surface.Slide15

Figure 17-12c Image Formation.

c

Light rays projected from a vertical

object show why the image arrives

upside down. (Note that the image

is also reversed.)

Optic

nerveSlide16

Figure 17-12d Image Formation.

d

Light rays projected from a horizontal

object show why the image arrives with

a left and right reversal. The image also

arrives upside down. (As noted in the

text, these representations are not

drawn to scale.)

Optic

nerveSlide17

Figure 17-13 Refractive Problems (Part 1 of 5).

The eye has a fixed

focal distance and

focuses by varying theshape of the lens.

A camera lens has a

fixed size and shapeand focuses by varying

the distance to the film.Slide18

Figure 17-13 Refractive Problems (Part 2 of 5).

Emmetropia

(normal vision)Slide19

Figure 17-13 Refractive Problems (Part 3 of 5).

Myopia

(nearsightedness)

If the eyeball is too deep or the resting

curvature of the lens is too great, the

image of a distant object is projected

in front of the retina. Myopic people

see distant objects as blurry and out

of focus. Vision at close range will be

normal because the lens is able to

round as needed to focus the image

on the retina.

Myopic corrected witha diverging,concavelens

DiverginglensSlide20

Figure 17-13 Refractive Problems (Part 4 of 5).

Hyperopia

If the eyeball is too shallow or the lens

is too flat, hyperopia results. The

ciliary muscle must contract to focus

even a distant object on the retina.And at close range the lens cannot

provide enough refraction to focus animage on the retina. Older peoplebecome farsighted as their lenses lose

elasticity, a form of hyperopia calledpresbyopia (

presbys, old man).

(farsightedness)

Hyperopia

corrected with

a converging,convexlens

ConverginglensSlide21

Figure 17-13 Refractive Problems (Part 5 of 5).

Surgical Correction

Variable success at correcting myopia and

hyperopia has been achieved by surgery that

reshapes the cornea. In photorefractive

keratectomy (PRK) a computer-guidedlaser shapes the cornea to exact specifications.

The entire procedure can be done in less thana minute. A variation on PRK is called

LASIK(Laser-Assisted in-Situ Keratomileusis

). In thisprocedure the interior layers of the cornea arereshaped and then recovered by the flap of original

outer corneal epithelium. Roughly 70 percent of LASIKpatients achieve normal vision, and LASIK has become the most

common form of refractive surgery. Even after surgery, many patients still need reading glasses,and both immediate and long-term visual problems can occur.Slide22

17-4 Visual PhysiologyVisual Physiology

Rods Respond to almost any photon, regardless of energy contentCones Have characteristic ranges of sensitivitySlide23

17-4 Visual PhysiologyAnatomy of Rods and Cones

Outer segment with membranous discsInner segmentNarrow stalk connects outer segment to inner segmentSlide24

17-4 Visual PhysiologyAnatomy of Rods and Cones

Visual pigmentsIs where light absorption occursDerivatives of rhodopsin (opsin plus retinal)Retinal synthesized from vitamin ASlide25

Figure 17-14a Structure of Rods, Cones, and Rhodopsin Molecule.

In a cone, the discs are

infoldings

of

the plasma membrane, and the outer

segment tapers to a blunt point.

In a rod, each disc is an independent

entity, and the outer segment forms

an elongated cylinder.

Discs

Connecting

stalks

Mitochondria

Golgi

apparatus

Nuclei

Pigment Epithelium

The pigment epithelium

absorbs photons that are

not absorbed by visual

pigments. It also

phagocytizes old discsshed from the tip of theouter segment.

Melanin granules

Outer Segment

The outer segment of a

photoreceptor contains

flattened membranous

plates, or

discs

, that

contain the visual pigments.

Cone

Rods

Inner Segment

The inner segment contains

the photoreceptor’s major

organelles and is responsible

for all cell functions other

than photoreception. It also

releases neurotransmitters.

Each photoreceptor

synapses with a bipolar cell.

Bipolar cell

LIGHT

Structure of rods and cones

aSlide26
Slide27

17-4 Visual PhysiologyColor Vision

Integration of information from red, green, and blue conesColor blindnessInability to detect certain colorsSlide28

Figure 17-21 The Anatomy of the Ear.

Elastic cartilages

External Ear

Auricle

Middle Ear

Auditory

ossicles

Oval

window

Internal Ear

Semicircular canals

Petrous part of

temporal bone

Facial nerve (VII)

Vestibulocochlear

nerve (VIII)

Bony labyrinth

of internal ear

Cochlea

Auditory tube

To

nasopharynx

Vestibule

Round

window

Tympanic

cavity

External acoustic

meatus

Tympanic

membraneSlide29

Figure 17-22a The Middle Ear.

Temporal bone

(petrous part)

Stabilizing

ligaments

Branch of facial

nerve VII (cut)

External

acoustic meatus

Malleus

Incus

Stapes

Auditory

Ossicles

Muscles of

the Middle Ear

Oval window

Tensor tympani

muscle

Stapedius

muscle

Round window

Auditory tube

Tympanic cavity

(middle ear)

Tympanic

membrane

The structures of the middle ear

aSlide30

17-5 The EarVibration of Tympanic Membrane

Converts arriving sound waves into mechanical movementsAuditory ossicles conduct vibrations to inner earTensor tympani muscleStiffens tympanic membrane Stapedius muscleReduces movement of stapes at oval windowSlide31

17-5 The EarThe

Internal Ear Contains fluid called endolymph Bony labyrinth surrounds and protects membranous labyrinthSubdivided into:VestibuleSemicircular canals

CochleaSlide32

Figure 17-23b The Internal Ear.

b

Semicircular

canal

Semicircular ducts

Anterior

Lateral

Posterior

Vestibule

Utricle

Saccule

Vestibular duct

Cochlear duct

The bony and membranous labyrinths. Areas of

the membranous labyrinth containing sensory

receptors (cristae, maculae, and spiral organ) are

shown in purple.

Cristae within

ampullae

Maculae

Endolymphatic

sac

KEY

Membranous

labyrinth

Bony labyrinth

Cochlea

Spiral

organ

Tympanic

ductSlide33

17-5 The EarThe Internal Ear

VestibuleEncloses saccule and utricle Receptors provide sensations of gravity and linear accelerationSemicircular canalsContain semicircular ducts Receptors stimulated by rotation of headSlide34

17-5 The EarThe Internal Ear

CochleaContains cochlear duct (elongated portion of membranous labyrinth) Receptors provide sense of hearingSlide35

17-5 The EarThe Internal Ear

Round window Thin, membranous partitionSeparates perilymph from air spaces of middle earOval windowFormed of collagen fibersConnected to base of stapesSlide36

17-5 The EarStimuli and Location

Sense of gravity and accelerationFrom hair cells in vestibuleSense of rotationFrom semicircular canalsSense of soundFrom cochleaSlide37

17-5 The EarEquilibrium

Sensations provided by receptors of vestibular complexHair cellsBasic receptors of inner earProvide information about direction and strength of mechanical stimuliSlide38
Slide39

17-5 The EarThe

Semicircular Ducts Are continuous with utricleEach duct contains:Ampulla with gelatinous cupulaAssociated sensory receptorsStereocilia – resemble long microvilliAre on surface of hair cellKinocilium

– single large ciliumSlide40

Figure 17-24a The Semicircular Ducts.

a

Semicircular ducts

Anterior

Posterior

Lateral

Ampulla

Utricle

Vestibular branch (N VIII)

Cochlea

Endolymphatic

sac

Endolymphatic

duct

Maculae

Saccule

An anterior view of the right

semicircular ducts, the utricle,

and the

saccule

, showing the

locations of sensory receptors.Slide41

Figure 17-24b The Semicircular Ducts.

Ampulla

filled with

endolymph

Hair cells

Crista

ampullaris

Cupula

Supporting cells

Sensory nerve

A cross section through the ampulla of a semicircular duct.

bSlide42

Figure 17-24c The Semicircular Ducts.

Semicircular duct

Endolymph

movement along the length of the duct

moves the

cupula

and stimulates the hair cells.

c

Cupula

Direction of

duct rotation

Direction of relative

endolymph

movement

Direction of

duct rotation

At restSlide43

Figure 17-24d The Semicircular Ducts.

Displacement in

this direction

stimulates hair cell

Displacement in

this direction

inhibits hair cell

Kinocilium

Hair cell

Gelatinous

material

Stereocilia

Sensory nerve

ending

Supporting cell

A representative hair cell (receptor) from the

vestibular complex. Bending the

sterocilia

towardthe kinocilium depolarizes the cell and stimulatesthe sensory neuron. Displacement in the oppositedirection inhibits the sensory neuron.

dSlide44

17-5 The EarThe Utricle and

Saccule Provide equilibrium sensationsAre connected with the endolymphatic duct, which ends in endolymphatic sac Slide45

17-5 The EarThe Utricle and

Saccule MaculaeOval structures where hair cells cluster StatoconiaDensely packed calcium carbonate crystals on surface of gelatinous massOtolith (ear stone)  gelatinous matrix and statoconiaSlide46

Figure 17-25ab The

Saccule

and Utricle.

Endolymphatic

sac

Endolymphatic

duct

Utricle

Saccule

The location of

the maculae

a

Otoliths

Gelatinous layer

forming

otolithic

membrane

Hair cells

Nerve fibers

The structure of an individual macula

bSlide47

Figure 17-25c The

Saccule

and Utricle.Head in normal, upright position

Gravity

1

2

Receptor

output

increases

Head tilted posteriorly

Otolith

moves

“downhill,”

distorting hair

cell processes

Gravity

A diagrammatic view of

utricular macular functionwhen the head is held normally and then tiltedback

1

2

cSlide48

17-5 The EarHearing

Cochlear duct receptors Provide sense of hearingSlide49

Figure 17-27a The Cochlea.

Scala

vestibuli

Cochlear duct

Scala

tympani

Cochlear

branch

Vestibular

branch

Vestibulocochlear

nerve (VIII)

Round window

Stapes at

oval window

From oval window

to tip of spiral

From tip of spiral

to round window

KEY

Semicircular

canals

The structure of the cochlea

aSlide50

Figure 17-27b The Cochlea.

Vestibular

membrane

Tectorial

membrane

Basilar

membrane

From oval

window

To round

window

Diagrammatic and sectional views of the cochlear spiral

b

Temporal bone

(petrous part)

Scala

vestibuli

(contains perilymph)

Cochlear duct

(contains

endolymph

)

Spiral organ

Spiral ganglion

Scala

tympani

(contains perilymph)

Cochlear nerve

Vestibulocochlear

nerve (VIII)Slide51

Figure 17-28a The Spiral Organ.

Bony cochlear wall

Scala

vestibuli

Vestibular membrane

Cochlear duct

Tectorial membrane

Basilar membrane

Scala

tympani

Spiral organ

Spiral

ganglion

Cochlear branch

of N VIII

A three-dimensional section of the

cochlea, showing the compartments,

tectorial membrane, and spiral organ

aSlide52

Figure 17-28b The Spiral Organ (Part 1 of 2).

Tectorial membrane

Outer

hair cell

Basilar

membrane

Inner

hair cell

Nerve

fibers

Diagrammatic and sectional views of the receptor

hair cell complex of the spiral organ

bSlide53

Figure 17-28b The Spiral Organ (Part 2 of 2).

Cochlear duct

Vestibular membrane

Tectorial membrane

Scala

tympani

Basilar

membrane

Hair cells

of spiral

organ

Spiral ganglion

cells of

cochlear nerve

Spiral organ

LM

×

125

Diagrammatic and sectional views of the receptor

hair cell complex of the spiral organ

bSlide54

17-5 The EarAn Introduction to Sound

Pressure waves Consist of regions where air molecules are crowded together Adjacent zone where molecules are farther apart Sine wavesS-shaped curvesSlide55

17-5 The EarPressure Wave

WavelengthDistance between two adjacent wave troughsFrequencyNumber of waves that pass fixed reference point at given time Physicists use term cycles instead of wavesHertz (Hz) number of cycles per second (cps)Slide56

17-5 The EarPressure Wave

Pitch Our sensory response to frequencyAmplitudeIntensity of sound wave Sound energy is reported in decibelsSlide57

Figure 17-29a The Nature of Sound.

Wavelength

Tympanic

membrane

Air

molecules

Tuning

fork

Sound waves (here, generated by a tuning fork)

travel through the air as pressure waves.

aSlide58

Figure 17-30 Sound and Hearing (Part 1 of 2).

External

acoustic

meatus

Malleus

Incus

Stapes

Oval

window

Movement

of sound

waves

Tympanic

membrane

Round

window

1

2

3

Sound wavesarrive attympanicmembrane.

Movement ofthe tympanicmembrane causes

displacementof the auditoryossicles

Movement of

the stapes at

the oval window

establishes

pressure waves

in the perilymph

of the

scala

vestibuli

.

1

2

3Slide59

Figure 17-30 Sound and Hearing (Part 2 of 2).

5

4

6

4

5

6

Cochlear branch

of cranial nerve VIII

Scala

vestibuli

(contains perilymph)

Vestibular membrane

Cochlear duct

(contains

endolymph

)

Basilar membrane

Scala

tympani

(contains perilymph)

The pressure

waves distort

the basilar

membrane on

their way to the

round window

of the

scala

tympani.

Vibration of

the basilar

membrane

causes hair cells

to vibrate against

the tectorial

membrane.

Information about

the region and

the intensity of

stimulation is

relayed to the CNS

over the cochlear

branch of cranial

nerve VIII.Slide60
Slide61

17-5 The EarAuditory Pathways

Cochlear branchFormed by afferent fibers of spiral ganglion neuronsEnters medulla oblongata Synapses at dorsal and ventral cochlear nuclei Information crosses to opposite side of brainAscends to inferior colliculus of midbrainSlide62

17-5 The EarAuditory Pathways

Ascending auditory sensationsSynapse in medial geniculate nucleus of thalamusProjection fibers deliver information to auditory cortex of temporal lobeSlide63

Figure 17-32 Pathways for Auditory Sensations (Part 1 of 2).

Primary pathway

Secondary pathway

Motor output

KEY

Stimulation of hair cells at

a specific location along

the basilar membrane

activates sensory neurons.

Sensory neurons carry the

sound information in the

cochlear branch of the

vestibulocochlear

nerve

(VIII) to the cochlear

nucleus on that side.

Cochlea

Low-frequencysounds

High-frequencysounds

Vestibularbranch

Vestibulocochlearnerve (VIII)

1

2Slide64

Figure 17-32 Pathways for Auditory Sensations (Part 2 of 2).

Primary pathway

Secondary pathway

Motor output

KEY

3

4

5

6

Projection fibers then deliver

the information to specific

locations within the auditory

cortex of the temporal lobe.

Low-frequency

sounds

Ascending acoustic

information goes to the

medial geniculate nucleus.

The inferior

colliculi

direct a variety of

unconscious motor responses to sounds.

To reticular formation

and motor nuclei of

cranial nerves

Superior

olivary

nucleus

Information ascends from each cochlear

nucleus to the superior

olivary

nucleus of the

pons and the inferior

colliculi

of the midbrain.

High-

frequency

sounds

Thalamus

To

ipsilateral

auditory

cortex

Motor output

to spinal cord

through the

tectospinal

tractsSlide65

17-5 The EarHearing Range

From softest to loudest represents trillionfold increase in powerNever use full potential Young children have greatest rangeSlide66

Table 17-1 Intensity of Representative Sounds.Slide67

17-5 The EarEffects of Aging on the Ear

With age, damage accumulatesTympanic membrane gets less flexibleArticulations between ossicles stiffenRound window may begin to ossify