General sensation Composed of sensory receptors throughout the body. –General senses Touch,...

General sensation• Composed of sensory receptors throughout the body.

– General senses• Touch, pressure, pain, heat, cold, stretch, vibration.

– Special senses • Vision, hearing, equilibrium, olfaction, taste.

• Relative to the source of the stimuli.– Exteroceptors– Interoceptors– Propioceptors (sketetal muscle). Conscious.

• General structure (histology, activity 1)– Modified dendrites.

• Free nerve endings• Merkel discs in epidermis• Hair follicle receptors• Meissner corpuscles: light touch• Ruffini corpuscles: deep pressure and stretching.• Pacinian corpuscles: pressure recptor.• Muscle spindles• Golgi tendon organs

• Receptor physiology– Act as signal transducers. Direct relationship between importance and number of clustering of the receptors;

punctuate distribution.

Special Senses

1. Vision

2. Olfaction

3. Taste

4. Hearing and equilibrium

1. Vision

• Organ: Eye ball• Accessory structures

– Lacrimal apparatus.• Lacrimal gland: secretes tears; solution of salts and lyzozyme.• Lacrimal canals• Nasolacrimal canal

– Eyelids (papebrae)– Medial and lateral canthus– Caruncle– Conjunctiva. Mucus membrane that lines inner surface of eyelids. Stratified

squamous and stratified cilindrical epithelium.– Eyelashes– Ciliary glands: lubricate eyeball– Tarsal glands: lubricate eyeball– 6 extrinsic eye muscles

• Activity 1

Human Anatomy and Physiology, 7eby Elaine Marieb & Katja Hoehn

Copyright © 2007 Pearson Education, Inc.,publishing as Benjamin Cummings.

The eye and associated accessory structures

(a)

Eyelashes

Sclera(covered byconjunctiva)

Site whereconjunctivamerges withcornea

Lateralcommissure(canthus)

Iris

Medialcommissure(canthus)

Lacrimalcaruncle

Eyelid

Eyelid

Eyebrow

PupilPalpebralfissure



The lacrimal apparatus

Lacrimal sacLacrimalgland

Excretory ductsof lacrimal gland

Lacrimal punctum

Lacrimal canaliculus

Nasolacrimal duct

Inferior meatusof nasal cavity

Nostril



The eye and associated accessory structures

(b)

Levator palpebraesuperioris muscle

Orbicularisoculi muscleEyebrow

Tarsal plate

PalpebralconjunctivaTarsalglands

Cornea

Palpebralfissure

Eyelashes

Bulbarconjunctiva

Conjunctivalsac

Orbicularisoculi muscle



Extrinsic eye muscles

(a) (b)

(c)

Opticnerve

Inferiorrectusmuscle

Inferiorobliquemuscle

Superior oblique muscle

Annular ring

Trochlea

Superior oblique tendon

Superior rectus muscle

Lateral rectus muscle

Conjunctiva

Axis atcenterof eye

Medialrectus muscle

Inferiorrectus muscle

Lateralrectus muscle

Lateral rectusMedial rectusSuperior rectusInferior rectusInferior obliqueSuperior oblique

Name Action

Moves eye laterallyMoves eye mediallyElevates eye and turns it mediallyDepresses eye and turns it mediallyElevates eye and turns it laterallyDepresses eye and turns it laterally

VI (abducens)III (oculomotor)III (oculomotor)III (oculomotor)III (oculomotor)IV (trochlear)

Controlling cranialnerve

Internal structure of the eye• Composed of 3 layers or tunics

– External• Cornea (transparent) and Sclera (white).

– Middle• Anterior

– Iris: radial smooth muscle (III ocoulomotor)– Uvea: vasculariazed. – Cilliar body(muscles) : control the curvature of the lens (cristaline).– Cilliary processes: secrete aqueous humor.

• Posterior– Choroid: dark pigment.

– Inner• Retina: sensory region

• Additional internal structures – Humor vitreous– Macula lutea (yellow spot): high cone density– Fovea centralis: area of maximum (very high amount of cones) sight acuity.– Sclera venous sins( Schlemm canal)– Ciliary zonule

• Activity 2 (eye dissection next class)



Internal structure of the eye (sagittal section)

(a)

Ora serrata

Ciliary body

Ciliary zonule(suspensoryligament)

Cornea

Iris

Anteriorpole

Pupil

Anteriorsegment(cavity)

Lens

Scleral venous sinus(Canal of Schlemm)

Posterior segment (cavity) (contains vitreous humor)

Optic nerve

Posterior pole

Fovea centralis

Macula lutea

Retina

Choroid

Sclera

Central arteryand vein of the retina

Optic disc(blind spot)



Circulation of aqueous humor

Sclera

Bulbarconjunctiva

Anterior ciliary vein

Scleral venous sinus

Posterior chamber

Anterior chamberAnteriorsegment

Limbus (corneal-scleral junction)

Cornea

Cornea

Corneal epithelium

Corneal endothelium

Aqueous humor

Iris

Lens

Lens epithelium

Lens

Posterior segmentcontaining vitreoushumor

Ciliary zonule(suspensoryligament)

Ciliaryprocesses

Ciliarymuscle

Ciliary body

ANTERIOR



Focusing for distant and close vision

(a) Lens is flattened for distant vision

(b) Lens bulges for close vision

(c) Anterior segment viewed from behind

Lens

Invertedimage

Ciliary zonule

Ciliary muscle

Nearly parallel raysfrom distant object

Sympathetic +

Divergent raysfrom close object

Invertedimage

Parasympathetic +

Ciliary muscle

Lens

Ciliary zonule(suspensory ligaments)

Histology of the retina

• Sensory tunic– Outer pigmented epithelial layer

– Inner neural layer. • Photoreceptors: cones or rods.

• Bipolar neurons

• Ganglion

• Axons of ganglions

• Activity 3



Photoreceptors of the retina

Process ofbipolar cell

Outerfiber

Apical microvillus

Discs containingvisual pigments

Inn

er s

egm

ent

Melaningranules

Pigment cellnucleus

Innerfibers

Rod cellbody

Cone cellbody

SynapticterminalsRod cellbody

Nuclei

Mitochondria

Connectingcilia

Ou

ter

seg

men

t

Pig

men

ted

lay

er

Basal lamina(border with choroid)

Retinal

Opsin

Discs beingphagocytized

(a)

(b)Li

ght

Lig

ht

Lig

ht



Visual fields of the eyes and visual pathway to the brain, inferior view

(a) (b)

Pretectalnucleus

Right eye Left eye

Fixationpoint

Opticradiation

Superiorcolliculus(sectioned)

Lateralgeniculatebody

Optic tractOptic chiasma

Uncrossed (ipsilateral) fiberCrossed (contralateral) fiber

Optic nerve

Lateral geniculatebody of thalamus

Superior colliculusOccipital lobe (visual cortex) Corpus callosum

Supra-chiasmaticnucleus

2. Olfaction

• Sensory structure:– Olfactory epithelium. Chemoreceptor.

• Olfactory receptor cell: bipolar neuron (I)

• Support cells: pseudo stratified ciliated epithelium.

• Basal cells.

• Activity 1



Olfactory receptors

Mitral cell

Olfactorygland

Olfactorytract

Olfactoryepithelium

Filaments of olfactory nerve

Cribriform plateof ethmoid bone

Lamina propria connective tissue

Basal cell

Supporting cell

Dendrite

Olfactory cilia

Glomeruli

Axon

Olfactory receptorcell

Mucus

Route of inhaledair containing odormolecules

Frontal lobeof cerebrum

Nasalconchae

Route ofinhaled air

Olfactoryepithelium

Olfactory tractOlfactorybulb

Red: support cell

Blue:bipolar neuron

Green:basal cell

Green:Bowman’s gland cell

3. Taste

• Sensory structure– Taste bud. Chemoreceptor. Mechanoreceptor. Thermo

receptor. • Basic tastes: sweet, sour, salt, bitter.• Types (location in figure)

– Fungiform papillae (mushrooms)– Circunvallate papilla (globes)– Filiform papilla

• Cell types– Gustatory (taste) cells: bipolar neurons.– Support cells

• Activity 2

Fg: fungiform papillae

Fl: filliform papillae

Weather’s Fucntional Histology



(a)(b)

(c)

(d)

Fungiformpapillae

Taste bud

Circumvallate papilla

Epiglottis

Palatine tonsil

Foliatepapillae

Lingual tonsil Basal cell

Taste fibersof cranialnerve

Connective tissue

Gustatoryreceptorcells

Tastepore

Gustatoryhair

Stratifiedsquamousepitheliumof tongue

Gustatory (taste) cells Tastepore

Connective tissue

Basal cells

Location and structure of taste buds on the tongue



The gustatory pathway

Gustatorycortex(in insula)

Thalamicnucleus(ventralposteriormedialnucleus)

Pons

Solitary nucleusin medulla oblongata

Facialnerve (VII)

Glosso-pharyngealnerve (IX)

Vagus(nerve X)

4. Hearing and balance

• Organ: Ear (sensory receptor for hearing and equilibrium).– Outer ear. Hearing

• Auricle• External acoustic meatus• Tympanic membrane• Ceruminous glands

– Middle ear. Hearing• Tympanic cavity

– Osicles» Malleus (hammer)» Incus (anvil)» Staples (stirrup). Connects with the oval window.

• Pharingotimpanic tube. Pressure equalization of middle ear and environment.– Inner ear

• Bony and membranous labyrinth– Cochlea: hearing– Vestible: equilibrium– 3 perpendicular semicircular canals: equilibrium



Structure of the ear

(a)

External(outer) ear Middle

ear

Internal(inner) ear(labryinth)

Pharyngotympanic(auditory) tube

Externalacousticmeatus

Auricle(pinna)

Helix

Lobule

Tympanic membrane

Middle ear

• Middle ear. Hearing– Tympanic cavity

• Osicles– Malleus (hammer)

– Incus (anvil)

– Staples (stirrup). Connects with the oval window.

• Pharingotimpanic tube. Pressure equalization of middle ear and environment.



Structure of the middle ear

(b)

Pharyngotympanic(auditory) tube

Auditoryossicles

Entrance to mastoid antrum in the epitympanic recess

Tympanicmembrane

Semicircularcanals

Cochlea

Cochlearnerve

Vestibularnerve

Oval window(deep to stapes)

Round window

Incus(anvil)

Malleus(hammer)

Stapes(stirrup)

Internaljugular vein

Vestibule

Externalacousticmeatus



The three auditory ossicles in the right middle ear

Pharyngotym-panic tube

Tensortympanimuscle

Tympanicmembrane(medial view)

Stapes

Malleus

Superior

Anterior

Incus Epitympanic recess

Stapediusmuscle

Inner ear

• Inner ear– Bony labyrinth

• Contains perilymph; similar composition to CSF since it is connected to the arachnoid space.

– Membranous labyrinth• Suspended in perilymph, contains endolymph.• Divisions:

– Cochlea: organ of Corti, hearing VIII.– Vestible:

» utricle and sacule. Macula; vertcial acceleration (equilibrium).– 3 perpendicular semicircular canals

» Semicircular duct. Ampula; angular acceleration (equilibrium).



• Anterior

Semicircular ducts insemicircular canals:

• Posterior

• Lateral

Cristae ampullaresin the ampullae

Utricle in vestibule

Saccule in vestibule

Stapes inoval window

Temporalbone

Facial nerve

Vestibular nerve

Superior vestibular ganglion

Inferior vestibular ganglion

Cochlear nerve

Maculae

Spiral organ (of Corti)

Cochlear duct in cochlea

Round window

Membranous labyrinth of the internal ear



Anatomy of the cochlea

(a)

Ovalwindow

Round window

Helicotrema

ModiolusCochlear nerve,division of thevestibulocochlearnerve (VIII)

Cochlear duct(scala media)

Spiral ganglion

Osseousspiral lamina

Vestibularmembrane




(b)

Cochlear duct(scala media)

Tectorialmembrane

Vestibularmembrane

Scala vestibuli

Scala tympaniBasilar

membrane

Spiralorgan(of Corti)

Striavascularis

Spiralganglion

Osseousspirallamina




(c)

Tectorialmembrane

Inner hair cell

Outer hair cells

Hairs (stereocilia)Afferent nervefibers

Basilarmembrane

Fibers ofcochlearnerve

Supportingcells

Hearing physiology

• Sound waves travel from the outer ear (timpanic membrane) middle ear (Malleus,Incus, staples, oval window) inner ear (scala tympani)/scala vestibuli stimulates the stereocillia of the organ of corti VIII

• The round window serves as a pressure relief valve.



Sound: source and propagation

(a) (b)

(c)

Area ofcompressedmolecules

Crest

Trough

Time Amplitude

Area ofrarefaction

Wavelength

Air

pre

ssu

re



Route of sound waves through the ear

Fluids in cochlear canals

Upper and middle

Internal earExternal ear

PinnaExternalacousticmeatus

Air

Tympanicmembrane

Malleus, incus,stapes

(ossicles)

Ovalwindow Lower

Middle ear

Onevibration

TimeSpiral organ

(of Corti)stimulated

Amplificationin middle ear

Amplitude

Pre

ssu

re



Resonance of the basilar membrane and activation of the cochlear hair cells

(a)

(b) (c)

Stapes

Ovalwindow

Scalavestibuli

Cochlearduct

Scalatympani

Basilarmembrane

Roundwindow

Base

Hz20,000

(High notes)

Hz1500

Hz500

500 Hz

4000 Hz

24,000 HzHz20

(Low notes)

Apex

Perilymph

Cochlearnerve

Relativelengthsof basilarfiberswithindifferentregionsof basilarmembrane

Basilarmembrane



Simplified diagram of the auditory pathway to the auditory cortex of the brain

Medialgeniculatebody ofthalamus

Primary auditorycortex in temporal lobe

Inferior colliculus

Lateral lemniscus

Superior olivarynucleus (pons-medulla junction)

Spiral organ(of Corti)

Bipolar cell

Spiral ganglionof cochlear nerve

Vestibulocochlearnerve

Medulla

Midbrain

Cochlear nuclei

Vibrations

Vibrations

Equilibrium physiology

• Located in the vestibular apparatus– Vestible

• Utricle and saccule (sacs) within vesitble.– Receptor: Macculae (static equilibrium)

» Hair cells (stereocillia) are embedded in the otholitic membrane which contain CaCO3 (otoliths). Respond to vertical acceleration.

– Membranous semicircular ducts• Ampulla (located at the base of each perpendicular duct).

Mechism of dynamic equilibrium (angular acceleration).– Receptor: Crista ampullaris. Stereocilia covered by a

gelatinous cupula. Endolymph stimulates the recptor.



Structure of a macula

Macula ofutricle

Macula ofsaccule

Otoliths

Hair bundle

KinociliumStereocilia Otolithic

membrane

Vestibularnerve fibers

Hair cells

Supportingcells



The effect of gravitational pull on a macula receptor cell in the utricle

Otolithicmembrane

Kinocilium

Stereocilia

Receptorpotential

Nerveimpulsesgenerated investibular fiber

Depolarization

(Hairs bent towarkinocilium)

dHyperpolarization

(Hairs bent awayfrom kinocilium)

Increasedimpulse frequency

Excitation

Decreasedimpulse frequency

Inhibition

Macula within the utriculus (otolith chamber) (Bouins, H&E, Bar = 36.4 µm). 1. ciliated sensory cells; 2. sustenticular cells; 3. connective tissue; 4. cupula (gelatinous matrix); 5. globular sensory epithelium; 6. collagenous connective tissue; 7. otolith chamber; 8. cranium.



Location and sturcture of a crista ampullaris

(a)

(c) (d)

(b)

Cupula Cupula at rest

Position of cupuladuring turn

Turning motion

Fluid motion inducts

Afferent fibers of vestibular nerve

Increased firing Decreased firing

Position of cupuladuring turn

Ampulla of left ear

Ampulla ofright ear

Horizontal ducts

Flow ofendolymph

Cupula

Cristaampullaris

Fibers ofvestibular nerve



Pathways of the balance and orientation system

Input

Central nervoussystem processing

Output

Oculomotor control(cranial nerve nucleiIII, IV, VI)(eye movements)

Spinal motor control(cranial nerve nuclei XIand vestibulospinal tracts)(neck movements)

Vestibularreceptors

Visualreceptors

CerebellumVestibularnuclearcomplex

Reticularnuclei

Somaticreceptors

General sensation Composed of sensory receptors throughout the body. –General senses Touch,...

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