Chapter 12 Nervous System III - Senses

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 12Lecture

PowerPoint

2

2401Anatomy and Physiology I

Chapter 12

Susan [email protected]

Department of Biology

Paris Junior College

mailto:[email protected]

3

Hole’s Human Anatomyand Physiology

Twelfth Edition

Shier Butler Lewis

Chapter 12

Nervous System III: Senses


4

12.1: Introduction

• General senses• Receptors that are widely distributed throughout the body• Skin, various organs and joints

• Special senses• Specialized receptors confined to structures in the head • Eyes, ears, nose and mouth

5

12.2: Receptors, Sensation, and Perception

• Sensory receptors• Specialized cells or multicellular structures that collect information from the environment

• Stimulate neurons to send impulses along sensory (afferent) fibers to the brain

• Sensation• A feeling that occurs when brain becomes aware of sensory impulse

• Perception• A person’s view of the stimulus; the way the brain interprets the information

6

Pathways From Sensation to Perception (Example of an Apple)

7

Receptor Types• Chemoreceptors

• Respond to changes in chemical concentrations

• Pain receptors (nociceptors)• Respond to chemicals released during tissue damage

• Thermoreceptors• Respond to changes in temperature

• Mechanoreceptors• Respond to mechanical forces (touch, stretch, pressure)

• Photoreceptors• Respond to light

8

Sensory Impulses• Stimulation of receptor causes local change in its receptor potential

• A graded electrical current is generated that reflects intensity of stimulation

• If receptor is part of a neuron, the membrane potential may generate an action potential

• If receptor is not part of a neuron, the receptor potential must be transferred to a neuron to trigger an action potential

• Peripheral nerves transmit impulses to CNS where they are analyzed and interpreted in the brain

9

Sensations and Perception

• Projection• Process in which the brain projects the sensation back to the apparent source• It allows a person to pinpoint the region of stimulation

10

Sensory Adaptation• Ability to ignore unimportant stimuli

• Involves a decreased response to a particular stimulus from the receptors (peripheral adaptation) or along the CNS pathways leading to the cerebral cortex (central adaptation)

• Sensory impulses become less frequent and may cease

• Stronger stimulus is required to trigger impulses

11

12.3: General Senses

• Senses associated with skin, muscles, joints and viscera

• Three (3) groups:• Exteroceptive senses (exteroceptors)

• Senses associated with body surface such as touch, pressure, temperature, and pain

• Visceroceptive senses (interoceptors)• Senses associated with changes in the viscera such as blood pressure stretching blood vessels and ingestion of a meal

• Proprioceptive senses• Senses associated with changes in muscles and tendons such as at joints

12

Touch and Pressure Senses

Free nerve endings• Common in epithelial tissues• Simplest receptors• Sense itching

Tactile (Meissners) corpuscles• Abundant in hairless portions of skin and lips• Detect fine touch; distinguish between two points on the skin

Lamellated (Pacinian) corpuscles• Common in deeper subcutaneous tissues, tendons and ligaments• Detect heavy pressure and vibrations

13

Touch and Pressure Receptors

Epidermis

Dermis

(a)

(b)

(c)

Section ofskin

Free nerveendings

Epithelialcells

Sensory (afferent)nerve fiber

Epithelialcells

Tactile (Meissners) corpuscle(touch receptor)

Sensory (afferent) nerve fiber

Lamellated (Pacinian) corpuscle(pressure receptor)Connective tissuecells

Sensory (afferent) nerve fiber


© Ed Reschke

14

Temperature Senses• Warm receptors

• Sensitive to temperatures above 25oC (77o F)• Unresponsive to temperature above 45oC (113oF)

• Cold receptors• Sensitive to temperatures between 10oC (50oF) and 20oC (68oF)

• Pain receptors• Respond to temperatures below 10oC• Respond to temperatures above 45oC

15

Sense of Pain

• Free nerve endings

• Widely distributed

• Nervous tissue of brain lacks pain receptors

• Stimulated by tissue damage, chemical, mechanical forces, or extremes in temperature

• Adapt very little, if at all

16

Visceral Pain• Pain receptors are the only receptors in viscera whose stimulation produces sensations• Pain receptors respond differently to stimulation• Pain receptors are not well localized• Pain receptors may feel as if coming from some other part of the body• Known as referred pain…

17

Referred Pain• May occur due to sensory impulses from two regions following a common nerve pathway to brain

Appendix

Ureter

Lung and diaphragm

Heart

Stomach

Pancreas

Colon

Kidney

Urinary bladder

Liver andgallbladder

Smallintestine

Ovary(female)

Liver andgallbladder


18

Pain Nerve Pathways• Acute pain fibers

• A-delta fibers • Thin, myelinated• Conduct impulses rapidly• Associated with sharp pain• Well localized

• Chronic pain fibers• C fibers • Thin, unmyelinated• Conduct impulses more slowly• Associated with dull, aching pain• Difficult to pinpoint• Blocked by narcotics (controlled substances)• CCC (Chronic, C fibers, Controlled substances)

19

Regulation of Pain Impulses

• Thalamus • Allows person to be aware of pain

• Cerebral cortex • Judges intensity of pain • Locates source of pain• Produces emotional and motor responses to pain

• Pain inhibiting substances:• Enkephalins• Serotonin• Endorphins

20

12.1 Clinical Application

Treating Pain

21

Proprioception• Mechanoreceptors

• Send information to spinal cord and CNS about body position and length, and tension of muscles

• Main kinds of proprioceptors:• Pacinian corpuscles – in joints• Muscle spindles – in skeletal muscles*• Golgi tendon organs – in tendons*

*considered to be stretch receptors

22

Stretch Receptors

(a)

Muscle spindle Skeletal muscle fiber

Golgi tendon organ

Tendon

(b)


Sensory nerve endings


Connectivetissue sheath

Intrafusalfiber

Skeletal musclefiber


23

Visceral Senses

• Receptors in internal organs

• Convey information that includes the sense of fullness after eating a meal as well as the discomfort of intestinal gas and the pain that signals a heart attack

24

Summary of Receptors of the General Senses

25

12.4: Special Senses• Sensory receptors are within large, complex sensory organs in the head

• Smell in olfactory organs

• Taste in taste buds

• Hearing and equilibrium in ears

• Sight in eyes

26

Sense of Smell

• Olfactory receptors• Chemoreceptors• Respond to chemicals dissolved in liquids

• Olfactory organs• Contain olfactory receptors and supporting epithelial cells• Cover parts of nasal cavity, superior nasal conchae, and a portion of the nasal septum

27

Olfactory ReceptorsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nasal cavityCilia

(b)(a)

CribriformplateOlfactory area ofnasal cavity

Superior nasalconcha

Olfactorybulb

Olfactorytract

Nerve fibers withinthe olfactory bulb

Olfactoryreceptor cells

Columnarepithelial cells

Cribriformplate

28

Olfactory Nerve Pathways

• Once olfactory receptors are stimulated, nerve impulses travel through• Olfactory nerves olfactory bulbs olfactory tracts limbic system (for emotions) and olfactory cortex (for interpretation)

29

Olfactory Stimulation

• Olfactory code• Hypothesis • Odor that is stimulated by a distinct set of receptor cells and its associated receptor proteins

• Olfactory organs located high in the nasal cavity above the usual pathway of inhaled air• Olfactory receptors undergo sensory adaptation rapidly• Sense of smell drops by 50% within a second after stimulation

30


Mixed-Up Senses: Synesthesia

31

Sense of Taste• Taste buds

• Organs of taste• Located on papillae of tongue, roof of mouth, linings of cheeks and walls of pharynx

• Taste receptors• Chemoreceptors• Taste cells – modified epithelial cells that function as receptors• Taste hairs –microvilli that protrude from taste cells; sensitive parts of taste cells

32

Taste Receptors

Papillae

(a)

(b)

ConnectivetissueSensory (afferent)nerve fibers

Epitheliumof tongue

Supportingcell

Tastepore

Taste hair

Taste cell

Taste buds


33

Taste Sensations

• Four primary taste sensations• Sweet – stimulated by carbohydrates• Sour – stimulated by acids• Salty – stimulated by salts• Bitter – stimulated by many organic compounds

• Spicy foods activate pain receptors

34

Taste Nerve Pathways

• Sensory impulses from taste receptors travel along:• Cranial nerves VII, IX, and X to… • Medulla oblongata to…• Thalamus to… • Gustatory cortex (for interpretation)

35


Smell and Taste Disorders

36

Sense of Hearing

• Ear• Organ of hearing

• Three (3) sections:• External ear• Middle ear• Inner ear

37

External Ear• Auricle

• Collects sounds waves

• External auditory meatus• Lined with ceruminous glands• Carries sound to tympanic membrane• Terminates with tympanic membrane

• Tympanic membrane • Vibrates in response to sound waves


Round window

PharynxAuditory tube

Auricle

Oval window(under stapes)

CochleaMalleus

Incus Stapes

External acousticmeatus

Semicircularcanals

Vestibulocochlearnerve

Tympanic cavity

Tympanicmembrane

38

Middle Ear


Round window


Auricle


CochleaMalleus

Incus Stapes


Semicircularcanals


Tympanic cavity

Tympanicmembrane

• Tympanic cavity• Air-filled space intemporal bone

• Auditory ossicles• Vibrate in response to tympanic membrane• Malleus, incus and stapes• Hammer, anvil and stirrup

• Oval window • Opening in wall of tympanic cavity• Stapes vibrates against it to move fluids in inner ear

39

Auditory Tube


Round window


Auricle


CochleaMalleus

Incus Stapes


Semicircularcanals


Tympanic cavity

Tympanicmembrane

• Also known as the Eustachian tube • Connects middle ear to throat• Helps maintain equal pressure on both sides of tympanic membrane• Usually closed by valve-like flaps in throat

Inner Ear

• Complex system of labyrinths

• Osseous labyrinth • Bony canal in temporal bone• Filled with perilymph

• Membranous labyrinth• Tube within osseous labyrinth• Filled with endolymph

Cochlear nerve

Maculae

Utricle

(a)Cochlea

Saccule

Ampullae

Endolymph

PerilymphMembranous labyrinth

Bony labyrinth

Vestibular nerve

Scalavestibuli (cut)Scalatympani (cut)Cochlearduct (cut)containingendolymph

VestibuleOvalwindow

Roundwindow

Semicircularcanals

Bony labyrinth(contains perilymph)

Membranous labyrinth(contains endolymph)


40

Inner Ear

Cochlear nerve

Maculae

Utricle

(a)Cochlea

Saccule

Ampullae

Endolymph

PerilymphMembranous labyrinth

Bony labyrinth

Vestibular nerve

Scalavestibuli (cut)Scalatympani (cut)Cochlearduct (cut)containingendolymph

VestibuleOvalwindow

Roundwindow

Semicircularcanals

Bony labyrinth(contains perilymph)

Membranous labyrinth(contains endolymph)


41

• Three (3) parts of labyrinths:• Cochlea

• Functions in hearing• Semicircular canals

• Functions in equilibrium

• Vestibule• Functions in equilibrium

42

Cochlea

• Scala vestibuli• Upper compartment• Leads from oval window to apex of spiral• Part of bony labyrinth

• Scala tympani• Lower compartment• Extends from apex of the cochlea to round window• Part of bony labyrinth

Stapes vibrating inoval window

Scala vestibulifilled with perilymph

Vestibularmembrane

BasilarmembraneScala tympanifilled withperilymph

Round window

Helicotrema

Membranouslabyrinth

Cochlear ductfilled with endolymph


43

Cochlea

• Cochlear duct• Portion of membranous labyrinth in cochlea

• Vestibular membrane• Separates cochlear duct from scala vestibuli

• Basilar membrane• Separates cochlear duct from scala tympani

Spiral organ (organ of Corti)

Basilar membrane

(a)

Scala vestibuli(contains perilymph)Vestibular membrane

Cochlear duct(contains endolymph)

Scala tympani(contains perilymph)

Branch ofcochlearnerve


44


Getting a Cochlear Implant

45

Organ of Corti

• Group of hearing receptor cells (hair cells)• On upper surface of basilar membrane• Different frequencies of vibration move different parts of basilar membrane• Particular sound frequencies cause hairs of receptor cells to bend• Nerve impulse generated

Spiral organ (organ of Corti)

Hair cells

Basilar membrane

(a)

(b)

Scala vestibuli(contains perilymph)

Cochlear duct(contains endolymph)

Scala tympani(contains perilymph)

Branch ofcochlearnerve

Tectorialmembrane

Basilarmembrane

Supportingcells

Nervefibers

Branch ofcochlear nerve

Vestibular membrane


46

Organ of Corti

Cochlear duct

Scala tympani Hair cells

(a)

(b)

Basilarmembrane

Tectorial membrane


a: © John D. Cunningham/Visuals Unlimited; b: © Fred Hossler/Visuals Unlimited

47

Auditory Nerve Pathways

Midbrain

Pons

Thalamus

Auditory cortex(temporal lobe)

Medial geniculatebody of thalamus

Superiorolivarynucleus

Medullaoblongata


Cochlearnuclei


48


Hearing Loss

49

Summary of the Generation of Sensory Impulses from the Ear

50

Sense of Equilibrium

• Static equilibrium• Vestibule• Senses position of head when body is not moving

• Dynamic Equilibrium• Semicircular canals• Senses rotation and movement of head and body

51

Vestibule• Utricle

• Communicates with saccule and membranous portion of semicircular canals

• Saccule• Communicates with cochlear duct

• Macula• Hair cells of utricle and saccule

Saccule

UtricleCochlea

Maculae

Ampullae ofsemicircularcanals


Cochlearduct


Vestibule

Macula• Responds to changes in head position• Bending of hairs results in generation of nerve impulse

Hair cells

Sensory (afferent) nerve fiber Supporting cells

Otoliths

(a) Head upright (b) Head bent forward

Maculaof utricle

Hairs ofhair cells bend

Gelatinousmaterial sags

Gravitationalforce


52

53

Semicircular Canals• Three (3) canals at right angles• Ampulla

• Swelling of membranous labyrinth that communicates with the vestibule

• Crista ampullaris• Sensory organ of ampulla• Hair cells and supporting cells• Rapid turns of head or body stimulate hair cells

Saccule

Utricle Cochlea

Maculae

Ampullae ofsemicircularcanals


Cochlearduct


Vestibule

54

Crista Ampullaris

Hair cell

Supporting cells

Sensory (afferent) nerve fibers

Hairs

Cupula Cristaampullaris

(a) Head in still position

(b) Head rotating


(c)

Crista ampullaris

Semicircular canal

Endolymph

Ampulla


55

Sense of Sight

• Visual accessory organs• Eyelids• Lacrimal apparatus• Extrinsic eye muscles

Eyelid• Palpebra• Composed of four (4) layers:

• Skin• Muscle • Connective tissue• Conjunctiva

• Orbicularis oculi – closes eyelid• Levator palpebrae superioris – opens eyelid• Tarsal glands – secrete oil onto eyelashes• Conjunctiva – mucous membrane; lines eyelid and covers portion of eyeball

Eyelash

Cornea

Conjunctiva

Eyelid

Tendon of levatorpalpebrae superioris

Superiorrectus

Orbicularisoculi

Inferiorrectus

Tarsal glands


56

Lacrimal Apparatus• Lacrimal gland

• Lateral to eye• Secretes tears

• Canaliculi• Collect tears

• Lacrimal sac• Collects from canaliculi

• Nasolacrimal duct• Collects from lacrimal sac• Empties tears into nasal cavity

Lacrimal gland

Lacrimal sac

Superior andinferior canaliculi

Nasolacrimalduct


57

Extrinsic Eye Muscles

Inferior rectus Inferior oblique

Medialrectus

Superiorrectus

Superioroblique

Lateralrectus(cut)


• Superior rectus• Rotates eye up and medially

• Inferior rectus• Rotates eye down and medially

• Medial rectus• Rotates eye medially

58

Extrinsic Eye Muscles

Inferior rectus Inferior oblique

Medialrectus

Superiorrectus

Superioroblique

Lateralrectus(cut)


• Lateral rectus• Rotates eye laterally

• Superior oblique• Rotates eye down and laterally

• Inferior oblique• Rotates eye up and laterally

59

60

Structure of the Eye

• Hollow• Spherical• Wall has three (3) layers:

• Outer fibrous tunic• Middle vascular tunic• Inner nervous tunic

Ciliary bodyRetinaChoroid coatSclera

Fovea centralis

Optic nerve

LensIris

PupilCornea

Lateral rectus

Medial rectus

Optic discPosterior cavity

Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

61

Outer Tunic


Fovea centralis

Optic nerve

LensIris

PupilCornea

Lateral rectus

Medial rectus


Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

• Cornea• Anterior portion• Transparent• Light transmission• Light refraction

• Sclera• Posterior portion• Opaque• Protection

62

Middle Tunic


Fovea centralis

Optic nerve

LensIris

PupilCornea

Lateral rectus

Medial rectus


Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

• Iris • Anterior portion• Pigmented• Controls light intensity

• Ciliary body• Anterior portion• Pigmented• Holds lens• Moves lens for focusing

• Choroid coat• Provides blood supply• Pigments absorb extra light

63

Anterior Portion of Eye• Filled with aqueous humor

Conjunctiva

Iris

Lens

Ciliary processCiliary muscles

Sclera

Cornea Anterior chamber

Vitreoushumor

Suspensoryligaments

Posteriorchamber

Ciliarybody


64

Lens

Conjunctiva

Iris

Lens


Sclera

Cornea Anterior chamber

Vitreoushumor

Suspensoryligaments

Posteriorchamber

Ciliarybody


Transparent, Biconvex , Lies behind iris, Composed of lens fibers, Elastic, Held in place by suspensory ligaments of ciliary body

65

Ciliary Body• Forms internal ring around the front of the eye• Ciliary processes – radiating folds• Ciliary muscles – contract and relax to move lens

RetinaChoroid coat

Sclera

Lens

Ciliary processesof ciliary bodySuspensoryligaments


66

Accommodation• Changing of lens shape to view objects

(a)

Lens thick

Lens thin

(b)

Ciliary musclefibers contractedSuspensoryligaments relaxed

Ciliary musclefibers relaxed

Suspensoryligaments taut


67

Iris

Sympatheticmotor nervefiber

In dim light


Radially arrangedSmooth muscle fibersof the irisCircularly arrangedsmooth muscle fibersof the iris

Pupil

In normal light In bright light

Parasympatheticganglion

Parasympatheticmotor nerve fiber

• Composed of connective tissue and smooth muscle• Pupil is hole in iris• Dim light stimulates radial muscles and pupil dilates• Bright light stimulates circular muscles and pupil constricts

68

Aqueous Humor• Fluid in anterior cavity of eye• Secreted by epithelium on inner surface of the ciliary body• Provides nutrients• Maintains shape of anterior portion of eye• Leaves cavity through Canal of Schlemm

Sclera

Iris

Lens

Aqueous humor

Cornea

Vitreous humor



Posteriorchamber

Ciliarybody

Scleral venous sinus(canal of Schlemm)

Anteriorchamber

69

Inner Tunic

• Retina• Contains visual receptors• Continuous with optic nerve• Ends just behind margin of the ciliary body• Composed of several layers• Macula lutea – yellowish spot in retina• Fovea centralis – center of macula lutea; produces sharpest vision• Optic disc – blind spot; contains no visual receptors• Vitreous humor – thick gel that holds retina flat against choroid coat

70

Posterior Cavity• Contains vitreous humor – thick gel that holds retina flat against choroid coat


Fovea centralis

Optic nerve

LensIris

Pupil

Cornea

Lateral rectus

Medial rectus


Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

71

Major Groups of Retinal Neurons

• Receptor cells, bipolar cells, and ganglion cells - provide pathway for impulses triggered by photoreceptors to reach the optic nerve• Horizontal cells and amacrine cells – modify impulses

Sclera

Receptor cellsRodCone

RetinaBipolar neuron

Ganglion cell

Nerve fibers

Horizontal cell

Amacrine cell

Light waves

Retinal pigmentepithelium

Pigmentedchoroidcoat

Impulsesto opticnerve

Vitreous humor

Layer ofconnectingneurons


72

Layers of the Eye

73

Light Refraction• Refraction

• Bending of light• Occurs when light waves pass at an oblique angle into mediums of different densities

Light wave

Perpendicular line

Air

Glass

Refractedlight wave


74

Types of Lenses• Convex lenses cause light waves to converge

• Concave lenses cause light waves to diverge

Air

Glass

(a) (b)

Diverginglight waves

Convexsurface

Lightwave

Converginglight waves

Concavesurface


75

Focusing On Retina• As light enters eye, it is refracted by:

• Convex surface of cornea• Convex surface of lens

• Image focused on retina is upside down and reversed from left to right

Light waves

Object Cornea

Image

Retina


76

Visual Receptors• Rods

• Long, thin projections• Contain light sensitive pigment called rhodopsin• Hundred times more sensitive to light than cones• Provide vision in dim light• Produce colorless vision• Produce outlines of objects

• Cones• Short, blunt projections• Contain light sensitive pigments called erythrolabe, chlorolabe, and cyanolabe• Provide vision in bright light• Produce sharp images• Produce color vision

77

Rods and Cones

ConesRods

Rod

Cone

(c)

Many sensory (afferent)nerve fibers(b)

Single sensory (afferent) nerve fiber(a)

Retinal pigmentepithelium


c: © Frank S. Werblin, PhD.

78

12.6 Clinical ApplicationRefraction Disorders

• Concave lens corrects nearsightedness

• Convex lens corrects farsightedness

Light waves

Light waves

Light waves

CorneaLens

Retina

(a) Eye too long (myopia)

(b) Normal eye

(c) Eye too short (hyperopia)

Pointof focus

Pointof focus

Pointof focus

Light waves

Concave lens

Convex lens

(a)

(b)

Uncorrectedpoint of focus

Correctedpoint of focus

Uncorrectedpoint of focus

Correctedpoint of focus


79

Visual Pigments

• Rhodopsin• Light-sensitive pigment in rods• Decomposes in presence of light• Triggers a complex series of reactions that initiate nerve impulses• Impulses travel along optic nerve

• Pigments on cones• Each set contains different light-sensitive pigment• Each set is sensitive to different wavelengths• Color perceived depends on which sets of cones are stimulated• Erythrolabe – responds to red• Chlorolabe – responds to green• Cyanolabe – responds to blue

80

Rod Cells

Mitochondria

Nucleus

Discs ofmembranewithin cell

Synapticending


81

Stereoscopic Vision• Provides perception of distance and depth• Results from formation of two slightly different retinal images

Lightwaves

Right eyeLeft eye


82

Visual Nerve Pathway

Optic tract

Eye

Fibers fromnasal (medial) halfof each retinacrossing over

Visual cortex ofoccipital lobe

Lateralgeniculatebody ofthalamus

Opticchiasma

Opticnerve

Opticradiations


83

12.5: Lifespan Changes• Age related hearing loss due to:

• Damage of hair cells in organ of Corti• Degeneration of nerve pathways to the brain• Tinnitus

• Age-related visual problems include:• Dry eyes• Floaters (crystals in vitreous humor)• Loss of elasticity of lens• Glaucoma• Cataracts• Macular degeneration

84

Important Points in Chapter 12:Outcomes to be Assessed

12.1: Introduction

Explain the difference between general senses and special senses.

12.2: Receptors, Sensation, and Perception

Name the five types of receptors and state the function of each.

Explain how receptors stimulate sensory impulses.

Explain how a sensation is produced.

12.3: General Senses

Distinguish between general and special senses.

Describe the differences among receptors associated with the senses of touch, pressure, temperature, and pain.

Describe how the sensation of pain is produced.

85

Important Points in Chapter 12:Outcomes to be Assessed

Explain the importance of stretch receptors in muscles and tendons.

12.4: Special Senses

Explain the relationship between the senses of smell and taste.

Name the parts of the ear and the function of each part.

Distinguish between static and dynamic equilibrium.

Name the parts of the eye and the function of each part.

Explain how the eye refracts light.

Explain how the brain perceives depth and distance.

Draw a diagram of the visual nerve pathways.

86

Quiz 12Complete Quiz 12 now!

Read Chapter 13.

Education

Chapter 12 Nervous System III - Senses