Transcript Peripheral Nervous System

THE PERIPHERAL NERVOUS
SYSTEM
D. C. MIKULECKY
PROFESSOR OF PHYSIOLOGY
AND
FACULTY MENTORING PROGRAM
ORGANIZATION OF THE
NERVOUS SYSTEM
BRAIN
SPINAL CORD
CENTRAL
NERVOUS
SYSTEM (CNS)
AFFERENT
EFFERENT
NERVES
NERVES
EXTEROINTERORECEPTORS RECEPTORS
EFFECTOR
ORGANS
PERIPHERAL
NERVOUS
SYSTEM
SOMATIC
SKELETAL
MUSCLES
AUTONOMIC
SMOOTH AND
CARDIAC MUSCLES
AND GLANDS
SENSORY INFORMATION TRAVELS
TO THE BRAIN VIA SPECIALIZED
PATHWAYS
NOSE
SMELL
EYE
VISION
TONGUE
TASTE
EAR
AUDITION
SKIN
SOMATIC
NEOCORTEX
LIMBIC
CORTEX
THALAMUS
BRAIN
STEM
SPINAL
CORD
SENSORY MODALITIES AND RECEPTOR CELLS
MODE
WARMTH
COLD
PAIN
RECEPTOR
NERVE ENDINGS
NERVE ENDINGS
NAKEDNERVE
ENDINGS
NERVE ENDINGS
JOINT
MOVEMENT &
POSITION
MUSCLE
NERVE ENDINGS
LENGTH
MUSCLE
NERVE ENDINGS
TENSION
ORGAN
SKIN
SKIN
SKIN
VARIOUS
MUSCLE
SPINDLE
GOLGI TENDON
ORGAN
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
VISION
HEARING
MOTION
SMELL
TASTE
RECEPTOR
ORGAN
RODS,CONES
EYE
HAIR CELLS EAR
HAIR CELLS VESTIBULAR
APPARATUS
TOUCHPRESSURE
NERVE ENDINGS
OLIFACTORY
NEURONS
TASTE RECEPTOR
CELLS
OLIFACTORY
MUCOUS MEMB.
TASTE BUDS
SKIN
SENSORY TRANSDUCTION
ADEQUATE
STIMULUS
MEMBRANE
CONDUCTANCE
CHANGE
GENERATOR
POTENTIAL
ACTION
POTENTIAL
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
BRAIN STEM.NEURON
ANTEROLATERAL
PATHWAY
INHIBITORY NEURON
PAIN
RECEPTOR
+
DORSAL HORN OF
SPINAL 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. MIKULECKY
PROFESSOR OF PHYSIOLOGY
AND
FACULTY 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 DUCT
AND
DRAINAGE
CANAL
PUPIL
IRIS
SCLERA
STRUCTURE OF THE EYE
SUSPENSORY LIGAMENT
CILIARY BODY
CONJUNCTIVA
IRIS
PUPIL
EXTERNAL EYE
MUSCLE
CHOROID
RETINA
SCLERA
FOVEA
LENS
CORNEA
AQUEOUS HUMOR
VITREOUS HUMOR
OPTIC NERVE
OPTIC DISC
BLOOD VESSELS
THE PHOTORECEPTORS
• RODS:
CYLLINDRICALLY
SHAPED- BROAD
RANGE OF
WAVELENGTHS,
NIGHT
• CONES: CONICALLY
SHAPED-NARROW
WAVELENGTH
RANGE, COLOR
BEFORE A PHOTON ARRIVES
MEMBRANE POLARIZED NORMALLY
AFTER A PHOTON ARRIVES
•RHODOPSIN ABSORBS PHOTON AND
CHANGES SHAPE
•A SEQUENCE OF BIOCHEMICAL STEPS
•MEMBRANE HYPERPOLARIZED
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. MIKULECKY
PROFESSOR OF PHYSIOLOGY
AND
FACULTY 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
SOUND
WAVE IN
EAR CANAL
TYMPANIC
MEMBRANE
BONES OF
MIDDLE EAR
COCHLEAR
FLUID
OVAL
WINDOW
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
COCHLEA
OVAL
WINDOW
STRUCTURE OF THE COCHLEA
OVAL
WINDOW
SCALA
VESTIBULI
COCHLEAR DUCT
SCALA
TYPANI
ROUND
WINDOW
STRUCTURE OF COCHLEAR
DUCT
TECTORIAL MEMBRANE
ORGAN OF CORTI
BASILAR MEMBRANE
TRANSDUCTION MECHANISM
TECTORIAL MEMBRANE STATIONARY
STEROCILIA
HAIR
CELLS
AUDITORY
NERVE
BASILAR MEMBRANE…..VIBRATES
TRANSDUCTION MECHANISM
TECTORIAL MEMBRANE STATIONARY
STEROCILIA
BEND
AUDITORY
NERVE
HAIR
CELLS
BASILAR MEMBRANE…..VIBRATES
FREQUENCY DISCRIMINATION:
LOCALIZATION OF DISPLACEMENT OF
BASILAR MEMBRANE
BASE
APEX
HIGH
MID
LOW
AUDITORY PATHWAYS
INFERIOR
COLLICULUS
SUPERIOR
OLIVE
VENTRAL
COCHLEAR
NUCLEUS
COCHLEA
VENTRAL
COCHLEAR
NUCLEUS
MIDLINE
AUDITORY PATHWAYS (CONT.)
TEMPORAL
CORTEX
TEMPORAL
CORTEX
MEDIAL
GENICULATE
MEDIAL
GENICULATE
INFERIOR
COLLICULUS
INFERIOR
COLLICULUS
SUPERIOR
OLIVE
MIDLINE
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 EACH
COORDINATE
PLANE
UTRICLE
&
SACCULUS
AMPULLA
THE UTRICLE & SACCULUS
OTOCONIA
(CALCIUM
CARBONATE
CRYSTALS)
NERVE
CELLS
OTOLITHIC
MEMBRANEGELATINOUS
LAYER
HAIR
CELLS
THE UTRICLE & SACCULUS
OTOCONIA
(CALCIUM
CARBONATE
CRYSTALS)
NERVE
CELLS
HEAD MOVEMENT
OTOLITHIC
MEMBRANEGELATINOUS
LAYER
HAIR
CELLS
THE VESTIBULAR APPARATUS:
SEMICIRCULAR CANALS
ONE CANAL
IN EACH
COORDINATE
PLANE
UTRICLE
&
SACCULUS
AMPULLA
THE AMPULLA
NERVE
CELLS
HAIR
CELLS
THE AMPULLA
MOVEMENT OF HEAD
INERTIAL FLUID
MOVEMENT
NERVE
CELLS
FIRE
HAIR
CELLS
BENT
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
THE AUTONOMIC NERVOUS SYSTEM
• TWO NEURON CHAINS
• SYMPATHETIC
• PARASYMATHETIC
TWO NEURON CHAINS
PRESYNAPTIC
NEURON
EFFECTOR
SPINE
ORGAN
POSTSYNAPTIC
NEURON
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 ANS
ORGAN
HEART
BLOOD
VESSELS
S
+
P
-
CONSTRICT(MOST
ORGANS)
DILATE (HEART
DILATE (PENIS
AND CLITORIS)
)
AND SKELETAL
BRONCHIOLES
DILATE
CONSTRICT
PUPIL
DIGESTION
DILATE
CONSTRICT
INHIBIT
ENHANCE