Chapter 12 Lecture PowerPoint D- sensory system Anatomy and Phyiology.

Chapter 12Lecture

PowerPoint

D- sensory systemAnatomy and Phyiology

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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

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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 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

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Pathways From Sensation to Perception (Example of an Apple)

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Receptor Types• Chemoreceptors

• Respond to changes in chemical concentrations

• Pain receptors (nociceptors)• Respond to tissue damage

• Thermoreceptors• Respond to changes in temperature

• Mechanoreceptors• Respond to mechanical forces

• Photoreceptors• Respond to light

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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

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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

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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

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Touch and Pressure Senses

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

Tactile (Meissner’s) 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

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Touch and Pressure Receptors

Epidermis

Dermis

(a)

(b)

(c)

Section ofskin

Free nerveendings

Epithelialcells

Sensorynerve fiber

Epithelialcells

Tactile (Meissner’s) corpuscle(touch receptor)

Sensory nervefiber

Lamellated(Pacinian) corpuscle(pressure receptor)

Connective tissuecells

Sensory nervefiber

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

b, c: © Ed Reschke

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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

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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

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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…

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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


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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

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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

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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

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Stretch Receptors

(a)

Muscle spindleSkeletal muscle fiber

Golgi tendon organ

Tendon

(b)

Sensorynerve fiber

Sensorynerve endings

Sensorynerve fiber

Connectivetissue sheath

Intrafusalfiber

Skeletal musclefiber


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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

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Summary of Receptors of the General Senses

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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

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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

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

Nasal cavityCilia

(b)(a)

Cribriformplate

Olfactory area ofnasal cavity

Superior nasalconcha

Olfactorybulb

Olfactorytract

Nerve fibers withinthe olfactory bulb

Olfactoryreceptor cells

Columnarepithelial cells

Cribriformplate

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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)

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Olfactory Stimulation

• 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

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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

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Taste Receptors

Papillae

(a)

(b)

Connectivetissue

Sensorynerve fibers

Epitheliumof tongue

Supportingcell

Tastepore

Taste hair

Taste cell

Taste buds


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Taste Sensations

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

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Taste Nerve Pathways

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

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Sense of Hearing

• Ear• Organ of hearing

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

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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)

Cochlea

Malleus

Incus Stapes

External acousticmeatus

Semicircularcanals

Vestibulocochlearnerve

Tympanic cavity

Tympanicmembrane

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Middle Ear


Round window


Auricle


Cochlea

Malleus

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

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Auditory Tube

• 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


Round window


Auricle


Cochlea

Malleus

Incus Stapes


Semicircularcanals


Tympanic cavity

Tympanicmembrane

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

Perilymph

Membranous labyrinth

Bony labyrinth

Vestibular nerve

Scalavestibuli (cut)

Scalatympani (cut)

Cochlearduct (cut)containingendolymph

VestibuleOvalwindow

Roundwindow

Semicircularcanals

Bony labyrinth(contains perilymph)

Membranous labyrinth(contains endolymph)


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Inner Ear

• Three (3) parts of labyrinths:• Cochlea

• Functions in hearing• Semicircular canals

• Functions in equilibrium• Vestibule

• Functions in equilibrium

Cochlear nerve

Maculae

Utricle

(a)

Cochlea

Saccule

Ampullae

Endolymph

Perilymph

Membranous labyrinth

Bony labyrinth

Vestibular nerve

Scalavestibuli (cut)

Scalatympani (cut)

Cochlearduct (cut)containingendolymph

VestibuleOvalwindow

Roundwindow

Semicircularcanals

Bony labyrinth(contains perilymph)

Membranous labyrinth(contains endolymph)


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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

Basilarmembrane

Scala tympanifilled withperilymph

Round window

Helicotrema

Membranouslabyrinth

Cochlear ductfilled with endolymph


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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


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Animation:Effect of Sound Waves on Cochlear Structures

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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


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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

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Auditory Nerve Pathways

Midbrain

Pons

Thalamus

Auditory cortex(temporal lobe)

Medial geniculatebody of thalamus

Superiorolivarynucleus

Medullaoblongata


Cochlearnuclei


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Summary of the Generation of Sensory Impulses from the Ear

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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

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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 nerve fiber Supporting cells

Otoliths

(a) Head upright (b) Head bent forward

Maculaof utricle

Hairs ofhair cells bend

Gelatinousmaterial sags

Gravitationalforce


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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

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Crista Ampullaris

Hair cell

Supporting cells

Sensory nerve fibers

Hairs

Cupula Cristaampullaris

(a) Head in still position

(b) Head rotating


(c)

Crista ampullaris

Semicircular canal

Endolymph

Ampulla


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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


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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


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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

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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

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Structure of the Eye

• Wall has three (3) layers:• Outer fibrous tunic• Middle vascular tunic• Inner nervous tunic Ciliary body

Retina

Choroid coat

Sclera

Fovea centralis

Optic nerve

Lens

Iris

Pupil

Cornea

Lateral rectus

Medial rectus

Optic disc

Posterior cavity

Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

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Outer Tunic

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

• Sclera• Posterior portion• Opaque• Protection

Ciliary body

Retina

Choroid coat

Sclera

Fovea centralis

Optic nerve

Lens

Iris

Pupil

Cornea

Lateral rectus

Medial rectus

Optic disc

Posterior cavity

Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

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Middle Tunic

• 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

Ciliary body

Retina

Choroid coat

Sclera

Fovea centralis

Optic nerve

Lens

Iris

Pupil

Cornea

Lateral rectus

Medial rectus

Optic disc

Posterior cavity

Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

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Anterior Portion of Eye• Filled with aqueous humor

Conjunctiva

Iris

Lens

Ciliary process

Ciliary muscles

Sclera

Cornea Anterior chamber

Vitreoushumor

Suspensoryligaments

Posteriorchamber

Ciliarybody


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Lens

• Transparent• Biconvex• Lies behind iris• Largely composed of lens fibers• Elastic• Held in place by suspensory ligaments of ciliary body

Conjunctiva

Iris

Lens

Ciliary process

Ciliary muscles

Sclera

Cornea Anterior chamber

Vitreoushumor

Suspensoryligaments

Posteriorchamber


Ciliarybody

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

Retina

Choroid coat

Sclera

Lens

Ciliary processesof ciliary body

Suspensoryligaments


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Accommodation• Changing of lens shape to view objects

(a)

Lens thick

Lens thin

(b)

Ciliary musclefibers contracted

Suspensoryligaments relaxed

Ciliary musclefibers relaxed

Suspensoryligaments taut


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Iris

Sympatheticmotor nervefiber

In dim light


Radially arrangedSmooth muscle fibersof the iris

Circularly 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

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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

Ciliary process

Ciliary muscles


Posteriorchamber

Ciliarybody

Scleral venous sinus(canal of Schlemm)

Anteriorchamber

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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

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Posterior Cavity

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

Ciliary body

Retina

Choroid coat

Sclera

Fovea centralis

Optic nerve

Lens

Iris

Pupil

Cornea

Lateral rectus

Medial rectus

Optic disc

Posterior cavity

Vitreous humor

Posteriorchamber

Anteriorchamber

Aqueoushumor

Suspensoryligaments


Anteriorcavity

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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 cellsRod

Cone

RetinaBipolar neuron

Ganglion cell

Nerve fibers

Horizontal cell

Amacrine cell

Light waves

Retinal pigmentepithelium

Pigmentedchoroidcoat

Impulsesto opticnerve

Vitreous humor

Layer ofconnectingneurons


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Layers of the Eye

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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


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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


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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

ObjectCornea

Image

Retina


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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

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Rods and Cones

ConesRods

Rod

Cone

(c)

Many sensorynerve fibers(b)

Single sensorynerve fiber(a)

Retinal pigmentepithelium


c: © Frank S. Werblin, PhD.

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12.6 Clinical ApplicationRefraction Disorders

• Concave lens corrects nearsightedness

• Convex lens corrects farsightedness

Light waves

Light waves

Light waves

Cornea

Lens

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


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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

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Rod Cells

Mitochondria

Nucleus

Rod cell

Discs ofmembranewithin cell

Synapticending


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

Lightwaves

Right eyeLeft eye


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Visual Nerve Pathway

Optic tract

Eye

Fibers fromnasal (medial) halfof each retinacrossing over

Visual cortex ofoccipital lobe

Lateralgeniculatebody ofthalamus

Opticchiasma

Opticnerve

Opticradiations


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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

Chapter 12 Lecture PowerPoint D- sensory system Anatomy and Phyiology.

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Transcript of Chapter 12 Lecture PowerPoint D- sensory system Anatomy and Phyiology.