THE PERIPHERAL NERVOUS SYSTEM

D. C. MIKULECKYPROFESSOR OF PHYSIOLOGY

ANDFACULTY MENTORING PROGRAM

ORGANIZATION OF THE NERVOUS SYSTEM

BRAINSPINAL CORD

CENTRALNERVOUSSYSTEM (CNS)

PERIPHERALNERVOUS SYSTEM

AFFERENT

NERVES

EFFERENT

NERVES

EXTERO-RECEPTORS

INTERO-RECEPTORS

SOMATIC AUTONOMIC

EFFECTORORGANS

SKELETALMUSCLES

SMOOTH AND CARDIAC MUSCLES AND GLANDS

NEOCORTEX

THALAMUS

LIMBICCORTEX

BRAINSTEM

SPINALCORD

NOSE

EYE

TONGUE

EAR

SKIN

SMELL

VISION

TASTE

AUDITION

SOMATIC

SENSORY INFORMATION TRAVELSTO THE BRAIN VIA SPECIALIZED PATHWAYS

SENSORY MODALITIES AND RECEPTOR CELLS

MODE RECEPTOR ORGANWARMTH NERVE ENDINGS SKINCOLD NERVE ENDINGS SKINPAIN NAKEDNERVE

ENDINGSSKIN

JOINTMOVEMENT &POSITION

NERVE ENDINGS VARIOUS

MUSCLELENGTH

NERVE ENDINGS MUSCLESPINDLE

MUSCLETENSION

NERVE ENDINGS GOLGI TENDONORGAN

GRADED VS ALL OR NONE

• A RECEPTOR’S RESPONSE TO A STIMULUS IS GRADED

• IF THRESHOLD IS EXCEEDED, THE ACTION POTENTIAL RESULTING IS ALL OR NONE

SENSORY MODALITIES AND RECEPTOR CELLS

MODE RECEPTOR ORGANVISION RODS,CONES EYEHEARING HAIR CELLS EARMOTION HAIR CELLS VESTIBULAR

APPARATUS

SMELL OLIFACTORYNEURONS

OLIFACTORYMUCOUS MEMB.

TASTE TASTE RECEPTORCELLS TASTE BUDS

TOUCH-PRESSURE

NERVE ENDINGS SKIN

SENSORY TRANSDUCTION

ADEQUATE STIMULUS

MEMBRANECONDUCTANCE

CHANGE

GENERATORPOTENTIAL

ACTIONPOTENTIAL

LOCALIZATION, DISTRIBUTION, AND ACUITY

• CODING OF LOCATION DEPENDS ON RECEPTOR LOCATION

• AREA COVERED BY RECEPTORS IN A SENSORY UNIT IS A RECEPTIVE FIELD

• ACUITY DEPENDS ON THE DENSITY OF RECEPTORS

SLOW PAIN

• OCCURS AFTER A SECOND OR MORE• OFTEN ASSOCIATED WITH TISSUE

DESTRUCTION• SUBJECTIVELY DESCRIBED AS BURNING,

ACHING,THROBBING, NAUSEOUS, OR CHRONIC

• C FIBERS WHICH SYNAPSE IN THE SUBSTANTIA GELITANOSA

• FINAL PROJECTION IS THE FRONTAL CORTEX

MECHANICAL, CHEMICAL AND THERMAL PAIN

• FAST PAIN IS GENERALLY MECHANICAL OR THERMAL

• SLOW PAIN CAN BE ALL THREE• CHEMICAL PAIN RECEPTORS:

BRADYKININ, SEROTONIN, HISTAMINE, POTASSIUM IONS, ACIDS, ACETYL CHOLINE AND PROTEOLYTIC ENZYMES

• PROSTAGLANDINS ENHANCE PAIN SENSATION

BRAIN STRUCTURES AND PAIN

• COMPLETE REMOVAL OF THE SENSORY CORTEX DOES NOT DESTROY THE ABILITY TO PERCIEVE PAIN

• STIMULATION OF THE SENSORY CORTEX EVOKES A SENSATION OF PAIN

PAIN CONTROL (ANALGESIA)

• THE ANALGESIA SYSTEM

• THE BRAIN’S OPIATE SYSTEM

• INHIBITION OF PAIN BY TACTILE STIMULATION

• TREATMENT OF PAIN BY ELECTRICAL STIMULATION

• REFERED PAIN

THE ANALGESIA SYSTEM

• PREAQUEDUCTAL GRAY

• RAPHE MAGNUS NUCLEUS

• PAIN INHIBITORY COMPLEX IN DORSAL HORNS

PAIN INHIBITORY COMPLEX: PRESYNAPTIC INHIBITION

PAINRECEPTOR

BRAIN STEM.NEURON

INHIBITORY NEURON

ANTEROLATERALPATHWAY

DORSAL HORN OFSPINAL CORD

+

-

PAIN TRANSMISSION AND INHIBITION

• SUBSTANCE P IS THE NEUROTRANSMITTER: BUILDS UP SLOWLY IN THE JUNCTION AND IS SLOWLY DESTROYED

• PRESYNAPTIC INHIBITION BY INHIBITORY NEURON BLOCKS THE RELEASE OF SUBSTANCE P (ENKEPHALIN)

THE BRAIN’S OPIATE SYSTEM

• OPIATE RECEPTORS EXIST IN MANY CENTERS OF THE BRAIN, ESPECIALLY IN THE ANALGESIA SYSTEM

• AMONG THE NATURAL SUBSTANCES WHICH ACTIVATE THESE RECEPTORS ARE: ENDORPHINS, ENKEPHALINS, AND MORPHINE

INHIBITION OF PAIN BY TACTILE STIMULATION

• STIMULATION OF LARGE SENSORY FIBERS FOR TACTILE SENSATION INHIBITS PAIN TRANSMISSION FOR SAME REGION

• RUBBING OFTEN EASES PAIN

• LINAMENTS, OIL OF CLOVE, ETC.

• POSSIBLE EXPLANATION FOR ACUPUNCTURE?

TREATMENT OF PAIN BY ELECTRICAL STIMULATION

• STIMULATION OF LARGE SENSORY NERVES

• ELECTRODES IN SKIN OR SPINAL IMPLANTS

• INTRALAMINAR NUCLEUS OF THALAMUS

REFERED PAIN

• VISCERAL PAIN FIBERS SYNAPSE ON SAME SECONDARY NEURONS AS RECEIVE PAIN FIBERS FROM SKIN

THE VISUAL SYSTEM

D. C. MIKULECKYPROFESSOR OF PHYSIOLOGY

ANDFACULTY MENTORING PROGRAM

THE VISUAL SYSTEM SENSES ELEECTROMAGNETIC RADIATION

• ELECTROMAGNETIC RADIATION (EMR) SPANS THE ELECTROMAGNETIC SPECTRUM (EMS)

• FROM RADIO WAVES (VERY LONG) TO -RADIATION (VERY SHORT)

• VISIBLE LIGHT IS A SMALL PORTION OF THE SPECTRUM

• PHOTONS OF LIGHT INTERACT WITH MATTER

ANATOMICAL ORGANIZATION

• THE EYE• CORNEA AND LENS: BEND LIGHT RAYS

AND FOCUS THEM ON THE RETINA• CILLIARY MUSCLES LOSSEN OR TIGHTEN

TO ADJUST LENS THICKNESS• RETINA: SITE OF PHOTORECEPTORS• FOVEA: MOST SENSITVE PART OF RETINA

TEAR DUCTANDDRAINAGECANAL

PUPIL IRISSCLERA

OPTIC DISC

OPTIC NERVE

BLOOD VESSELS

FOVEA

SCLERA

RETINA

CHOROID

VITREOUS HUMOR

AQUEOUS HUMOR

CORNEA

LENS

PUPIL

IRIS

CONJUNCTIVACILIARY BODY

SUSPENSORY LIGAMENTEXTERNAL EYEMUSCLE

STRUCTURE OF THE EYE

THE PHOTORECEPTORS• RODS:

CYLLINDRICALLY SHAPED- BROAD RANGE OF WAVELENGTHS, NIGHT

• CONES: CONICALLY SHAPED-NARROW WAVELENGTH RANGE, COLOR

BEFORE A PHOTON ARRIVES

•RHODOPSIN ABSORBS PHOTON AND CHANGES SHAPE

•A SEQUENCE OF BIOCHEMICAL STEPS

•MEMBRANE HYPERPOLARIZED

AFTER A PHOTON ARRIVES

MEMBRANE POLARIZED NORMALLY

PATHWAYS FOR VISUAL INFORMATION

• OPTIC NERVE (GANGLION CELLS FROM RETINA)

• LEAVES THROUGH “BLIND SPOT”

• LATERAL GENICULATE NUCLEUS: PROJECTS TO CORTEX

• PRIMARY VISUAL CORTEX

VISUAL ORIENTATION COLUMNS

• CELLS IN VARIOUS COLUMNS OF CORTEX RESPOND TO DIFFERENT ORIENTATIONS

• THESE DEVELOP DURING THE EARLY VISUAL EXPERIENCES OF YOUNG ANIMALS

COLOR VISION

• TRICHROMATIC: RED, BLUE, GREEN

• PARVOCELLULAR NEURONS CARRY INFORMATION

• DIFFERENT CELL TYPES

• COLOR CONTRAST

THREE KINDS OF CONES

• RED, BLUE, AND GREEN

• CONNECT TO SMALL GANGLION CELLS

• TRANSMIT COLOR INFORMATION TO PARVOCELLULAR NEURONS IN LGN

COLOR NEURONS

• BROAD BAND: SINGLE COLOR, + INSIDE, - OUT

• SINGLE - OPPONENT: EXITED BY ONE COLOR IN CENTER, INHIBITED WHEN ANOTHER COLOR IN PERIPHERY

• DOUBLE OPPONENT: OPPOSING COLORS IN BOTH CENTER AND PERIPHERY

• ANNULAR FIELDS OVERLAP TO RECTANGULAR IN CORTEX

LENS DEFECTS

• FOCUSING IN FRONT OF RETINA

• NEARSIGHTEDNESS (MYOPIA)

• USUALLY DUE TO WEAK CILIARY MUSCLES

• FOCUSING BEHIND THE RETINA

• FARSIGHTEDNESS(HYPEROPIA)

• LENS TOO STIFF (AGING)

NEARSIGHTEDNESS (MYOPIA)

UNCORRECTED

CORRECTED

FARSIGHTEDNESS (HYPEROPIA)

UNCORRECTED

CORRECTED

VISUAL FIELD DEFECTS

• OPTIC NERVE:VISUAL FIELD ON SAME SIDE

• OPTIC CHIASM:OUTER HALF OF BOTH VISUAL FIELDS

• OPTIC TRACT: OPPOSITE HALF IN BOTH VISUAL FIELDS

• OPTIC RADIATIONS:LOWER OR UPPER QUADRANT ON OPPOSITE SIDE

THE AUDITORY SYSTEM AND THE CHEMICAL SENSES

D. C. MIKULECKYPROFESSOR OF PHYSIOLOGY

ANDFACULTY MENTORING PROGRAM

THE NATURE OF SOUND

• COMPRESSION AND RARIFICATION OF AIR

• WAVES OF HIGH AND LOW PRESSURE

• TRANSMIT MECHANICAL FORCES

CHARACTERISTICS OF A PRESSURE WAVE

A

T = WAVELENGTH

A = AMPLITUDE

f = 1/T FREQUENCY

ANATOMY OF THE EAR

• OUTER EAR

• MIDDLE EAR

• INNER EAR

OUTER EAR

• ACTS TO FOCUS SOUND WAVES ON THE TYMPANIC MEMBRANE

• SHAPED LIKE A SOUND CONE

OUTER EAR

PINNA

CANAL

MIDDLE EAR

• THREE BONES LINK TYMPANIC MEMBRANE TO OVAL WINDOW

• VIBRATIONS TRANSMITTED MECHANICALLY

MIDDLE EAR

TYMPANICMEMBRANE

OVALWINDOW

BONES OFMIDDLE EAR COCHLEAR

FLUIDSOUNDWAVE IN EAR CANAL

INNER EAR

• SITE OF TRANSDUCTION

• VIBRATION OF COCHLEAR FLUID CAUSES BASILAR MEMBRANE TO VIBRATE

• HAIR CELLS ARE DEFORMED

• AUDITORY NERVE BECOMES EXCITED AS HAIR CELLS DEPOLARIZE

INNER EAR

OVALWINDOW

COCHLEA

STRUCTURE OF THE COCHLEA

SCALA VESTIBULI

COCHLEAR DUCT

SCALATYPANI

OVALWINDOW

ROUND WINDOW

STRUCTURE OF COCHLEAR DUCT

BASILAR MEMBRANE

TECTORIAL MEMBRANEORGAN OF CORTI

TRANSDUCTION MECHANISM

BASILAR MEMBRANE…..VIBRATES

TECTORIAL MEMBRANE STATIONARY

STEROCILIA

AUDITORY NERVE

HAIRCELLS

TRANSDUCTION MECHANISM

TECTORIAL MEMBRANE STATIONARY

BASILAR MEMBRANE…..VIBRATES

STEROCILIABEND

AUDITORY NERVE HAIR

CELLS

FREQUENCY DISCRIMINATION: LOCALIZATION OF DISPLACEMENT OF

BASILAR MEMBRANEBASE APEX

HIGH

LOW

MID

AUDITORY PATHWAYS

COCHLEA

VENTRALCOCHLEARNUCLEUS MIDLINE

VENTRALCOCHLEARNUCLEUS

SUPERIOROLIVE

INFERIOR

COLLICULUS

AUDITORY PATHWAYS (CONT.)

MIDLINE

SUPERIOROLIVE

INFERIOR COLLICULUS

INFERIOR COLLICULUS

MEDIAL GENICULATE

MEDIAL GENICULATE

TEMPORALCORTEX

TEMPORALCORTEX

CHARACTERISTICS OF A PRESSURE WAVE

A

T = WAVELENGTH

A = AMPLITUDE

f = 1/T FREQUENCY

PROPERTIES OF AUDITORY NERVE CELLS

• EACH AUDITORY NERVE FIBER HAS AN OPTIMUM FREQUENCY

• THIS TONOTOPIC ORGANIZATION ARISES FROM POSITION IN THE COCHLEA

• TONIC AND PHASIC NEURONS IN EACH AREA

• SOME RESPOND TO CHANGE IN FREQUENCY

• SOME RESPOND TO CHANGE IN AMPLITUDE

SOUND LOCALIZATION

• INTERAURAL TIME DIFFERENCE

• TIME DELAY BETWEEN TWO EARS

• ALSO INTENSITY DIFFERENCES

DISORDERS OF AUDITION

• LOSS OF HAIR CELLS: FREQUENCY SPECIFIC

• TINNITUS: RINGING

• CONDUCTIVE:l DAMAGE TO MIDDLE EAR

• CENTRAL: BRAIN TUMORS AND LESIONS

THE VESTIBULAR APPARATUS

• SEMICIRCULAR CANALS: HAIR CELLS SENSE MOTION

• THREE COORDINATE PLANES: SUPERIOR, INFERIOR, AND HORIZONTAL

• UTRICLE AND SACCULE DETECT LINEAR ACCELERATION IN HORIZONTAL AND VERTICLE PLANES

THE VESTIBULAR APPARATUS: UTRICLE & SACCULUS

ONE CANAL IN EACHCOORDINATEPLANE

AMPULLAUTRICLE&SACCULUS

THE UTRICLE & SACCULUS

HAIR CELLSNERVE

CELLS

OTOLITHICMEMBRANE-GELATINOUSLAYER

OTOCONIA(CALCIUMCARBONATECRYSTALS)

THE UTRICLE & SACCULUS

HAIR CELLSNERVE

CELLS

OTOLITHICMEMBRANE-GELATINOUSLAYER

OTOCONIA(CALCIUMCARBONATECRYSTALS)

HEAD MOVEMENT

THE VESTIBULAR APPARATUS: SEMICIRCULAR CANALS

ONE CANAL IN EACHCOORDINATEPLANE

AMPULLAUTRICLE&SACCULUS

THE AMPULLA

HAIR CELLSNERVE

CELLS

THE AMPULLA

HAIR CELLSBENT

NERVECELLSFIRE

INERTIAL FLUID MOVEMENT

MOVEMENT OF HEAD

TASTE SENSATION

• GUSTATORY RECEPTORS

• GUSTATORY PATHWAYS

GUSTATORY RECEPTORS

• TASTE BUDS ON TONGUE LOCALIZED

• SWEET: TIP

• BITTER:BACK

• SOUR SIDES

• SALT: FRONT

GUSTATORY PATHWAYS

• VII, IX, X CRANIAL NERVES

• TO GUSTATORY NUCLEUS IN BRAIN STEM

• VPM NUCLEUS OF THALAMUS

• GUSTATORY AREA OF NEOCORTEX

• VIA LIMBIC SYSTEM TO HYPOTHALAMUS

THE OLIFACTORY SYSTEM

• RECEPTOR CELLS IN OLIFACTORY MUCOSAL MEMBRANE

• AXONS CROSS CRIBIFORM PLATE AND TERMINATE ON MITRAL CELLS IN OLIFACTORY BULB-FORM OLIFACTORY TRACT

• OLIFACTORY TRACT GOES TO LIMBIC SYSTEM AND TO ORBITOFRONTAL CORTEX

• CLOSELY ASSOCIATED WITH EATING AND MATING BEHAVIOR

THE AUTONOMIC NERVOUS SYSTEM

• TWO NEURON CHAINS

• SYMPATHETIC

• PARASYMATHETIC

TWO NEURON CHAINS

SPINEEFFECTOR

ORGAN

PRESYNAPTICNEURON

POSTSYNAPTICNEURON

SYMPATHETIC

• GANGLION NEAR SPINE

• SHORT PREGANGLIONIC NEURONS

• LONG POSTGANGLIONIC NEURONS

• FLIGHT OR FIGHT

• POSTGANGLIONIC NEURONS ARE ADRENERGIC

PARASYMPATHETIC

• GANGLION NEAR EFFECTOR ORGAN

• LONG PREGANGLIONIC NEURONS

• SHORT POSTGANGLIONIC NEURONS

• “COUCH POTATO”

• POSTGANGLIONIC NEURONS ARE CHOLINERGIC

EFFECTS OF ANSORGAN S PHEART + -BLOODVESSELS

CONSTRICT(MOSTORGANS)

DILATE (HEART

AND SKELETAL)

DILATE (PENISAND CLITORIS)

BRONCHIOLES DILATE CONSTRICT

PUPIL DILATE CONSTRICT

DIGESTION INHIBIT ENHANCE