THE PERIPHERAL NERVOUS SYSTEM

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THE PERIPHERAL NERVOUS SYSTEM

• D. C. MIKULECKY
• PROFESSOR OF PHYSIOLOGY
• AND
• FACULTY MENTORING PROGRAM

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ORGANIZATION OF THE NERVOUS SYSTEM
BRAIN SPINAL CORD
CENTRAL NERVOUS SYSTEM (CNS)
AFFERENT NERVES
EFFERENT NERVES
PERIPHERAL NERVOUS SYSTEM
EXTERO- RECEPTORS
INTERO- RECEPTORS
SOMATIC
AUTONOMIC
EFFECTOR ORGANS
SKELETAL MUSCLES
SMOOTH AND CARDIAC MUSCLES AND GLANDS
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SENSORY INFORMATION TRAVELS TO THE BRAIN VIA
SPECIALIZED PATHWAYS
NEOCORTEX
LIMBIC CORTEX
NOSE
SMELL
THALAMUS
EYE
VISION
TASTE
TONGUE
BRAIN STEM
EAR
AUDITION
SKIN
SOMATIC
SPINAL CORD
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SENSORY MODALITIES AND RECEPTOR CELLS
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GRADED VS ALL OR NONE

• A RECEPTORS RESPONSE TO A STIMULUS IS GRADED
• IF THRESHOLD IS EXCEEDED, THE ACTION POTENTIAL
  RESULTING IS ALL OR NONE

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SENSORY MODALITIES AND RECEPTOR CELLS
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SENSORY TRANSDUCTION
ADEQUATE STIMULUS
MEMBRANE CONDUCTANCE CHANGE
GENERATOR POTENTIAL
ACTION POTENTIAL
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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

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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

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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

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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

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PAIN CONTROL (ANALGESIA)

• THE ANALGESIA SYSTEM
• THE BRAINS OPIATE SYSTEM
• INHIBITION OF PAIN BY TACTILE STIMULATION
• TREATMENT OF PAIN BY ELECTRICAL STIMULATION
• REFERED PAIN

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THE ANALGESIA SYSTEM

• PREAQUEDUCTAL GRAY
• RAPHE MAGNUS NUCLEUS
• PAIN INHIBITORY COMPLEX IN DORSAL HORNS

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PAIN INHIBITORY COMPLEX PRESYNAPTIC INHIBITION
BRAIN STEM.NEURON
ANTEROLATERAL PATHWAY
INHIBITORY NEURON
-
PAIN RECEPTOR

DORSAL HORN OF SPINAL CORD
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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)

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THE BRAINS 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

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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?

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TREATMENT OF PAIN BY ELECTRICAL STIMULATION

• STIMULATION OF LARGE SENSORY NERVES
• ELECTRODES IN SKIN OR SPINAL IMPLANTS
• INTRALAMINAR NUCLEUS OF THALAMUS

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REFERED PAIN

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

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THE VISUAL SYSTEM

• D. C. MIKULECKY
• PROFESSOR OF PHYSIOLOGY
• AND
• FACULTY MENTORING PROGRAM

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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

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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

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SCLERA
TEAR DUCT AND DRAINAGE CANAL
PUPIL
IRIS
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STRUCTURE OF THE EYE
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THE PHOTORECEPTORS

• RODS CYLLINDRICALLY SHAPED- BROAD RANGE OF
  WAVELENGTHS, NIGHT
• CONES CONICALLY SHAPED-NARROW WAVELENGTH RANGE,
  COLOR

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BEFORE A PHOTON ARRIVES
MEMBRANE POLARIZED NORMALLY
AFTER A PHOTON ARRIVES

• RHODOPSIN ABSORBS PHOTON AND CHANGES SHAPE
• A SEQUENCE OF BIOCHEMICAL STEPS
• MEMBRANE HYPERPOLARIZED

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PATHWAYS FOR VISUAL INFORMATION

• OPTIC NERVE (GANGLION CELLS FROM RETINA)
• LEAVES THROUGH BLIND SPOT
• LATERAL GENICULATE NUCLEUS PROJECTS TO CORTEX
• PRIMARY VISUAL CORTEX

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VISUAL ORIENTATION COLUMNS

• CELLS IN VARIOUS COLUMNS OF CORTEX RESPOND TO
  DIFFERENT ORIENTATIONS
• THESE DEVELOP DURING THE EARLY VISUAL EXPERIENCES
  OF YOUNG ANIMALS

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COLOR VISION

• TRICHROMATIC RED, BLUE, GREEN
• PARVOCELLULAR NEURONS CARRY INFORMATION
• DIFFERENT CELL TYPES
• COLOR CONTRAST

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THREE KINDS OF CONES

• RED, BLUE, AND GREEN
• CONNECT TO SMALL GANGLION CELLS
• TRANSMIT COLOR INFORMATION TO PARVOCELLULAR
  NEURONS IN LGN

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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

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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)

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NEARSIGHTEDNESS (MYOPIA)
UNCORRECTED
CORRECTED
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FARSIGHTEDNESS (HYPEROPIA)
UNCORRECTED
CORRECTED
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VISUAL FIELD DEFECTS

• OPTIC NERVEVISUAL FIELD ON SAME SIDE
• OPTIC CHIASMOUTER HALF OF BOTH VISUAL FIELDS
• OPTIC TRACT OPPOSITE HALF IN BOTH VISUAL FIELDS
• OPTIC RADIATIONSLOWER OR UPPER QUADRANT ON
  OPPOSITE SIDE

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THE AUDITORY SYSTEM AND THE CHEMICAL SENSES

• D. C. MIKULECKY
• PROFESSOR OF PHYSIOLOGY
• AND
• FACULTY MENTORING PROGRAM

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THE NATURE OF SOUND

• COMPRESSION AND RARIFICATION OF AIR
• WAVES OF HIGH AND LOW PRESSURE
• TRANSMIT MECHANICAL FORCES

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CHARACTERISTICS OF A PRESSURE WAVE
A
T WAVELENGTH A AMPLITUDE f 1/T FREQUENCY
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ANATOMY OF THE EAR

• OUTER EAR
• MIDDLE EAR
• INNER EAR

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OUTER EAR

• ACTS TO FOCUS SOUND WAVES ON THE TYMPANIC
  MEMBRANE
• SHAPED LIKE A SOUND CONE

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OUTER EAR
PINNA
CANAL
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MIDDLE EAR

• THREE BONES LINK TYMPANIC MEMBRANE TO OVAL WINDOW
  
• VIBRATIONS TRANSMITTED MECHANICALLY

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MIDDLE EAR
BONES OF MIDDLE EAR
COCHLEAR FLUID
SOUND WAVE IN EAR CANAL
TYMPANIC MEMBRANE
OVAL WINDOW
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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

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INNER EAR
COCHLEA
OVAL WINDOW
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STRUCTURE OF THE COCHLEA
OVAL WINDOW
SCALA VESTIBULI
COCHLEAR DUCT
SCALA TYPANI
ROUND WINDOW
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STRUCTURE OF COCHLEAR DUCT

TECTORIAL MEMBRANE ORGAN OF CORTI
BASILAR MEMBRANE
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TRANSDUCTION MECHANISM
TECTORIAL MEMBRANE STATIONARY
STEROCILIA
HAIR CELLS
AUDITORY NERVE
BASILAR MEMBRANE..VIBRATES
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TRANSDUCTION MECHANISM
TECTORIAL MEMBRANE STATIONARY
STEROCILIA BEND
AUDITORY NERVE
HAIR CELLS
BASILAR MEMBRANE..VIBRATES
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FREQUENCY DISCRIMINATION LOCALIZATION OF
DISPLACEMENT OF BASILAR MEMBRANE
BASE
APEX
HIGH
MID
LOW
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AUDITORY PATHWAYS
INFERIOR COLLICULUS
SUPERIOR OLIVE
VENTRAL COCHLEAR NUCLEUS
VENTRAL COCHLEAR NUCLEUS
COCHLEA
MIDLINE
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AUDITORY PATHWAYS (CONT.)
TEMPORAL CORTEX
TEMPORAL CORTEX
MEDIAL GENICULATE
MEDIAL GENICULATE
INFERIOR COLLICULUS
INFERIOR COLLICULUS
SUPERIOR OLIVE
MIDLINE
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CHARACTERISTICS OF A PRESSURE WAVE
A
T WAVELENGTH A AMPLITUDE f 1/T FREQUENCY
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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

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SOUND LOCALIZATION

• INTERAURAL TIME DIFFERENCE
• TIME DELAY BETWEEN TWO EARS
• ALSO INTENSITY DIFFERENCES

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DISORDERS OF AUDITION

• LOSS OF HAIR CELLS FREQUENCY SPECIFIC
• TINNITUS RINGING
• CONDUCTIVEl DAMAGE TO MIDDLE EAR
• CENTRAL BRAIN TUMORS AND LESIONS

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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

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THE VESTIBULAR APPARATUS UTRICLE SACCULUS
ONE CANAL IN EACH COORDINATE PLANE
UTRICLE SACCULUS
AMPULLA
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THE UTRICLE SACCULUS
OTOCONIA (CALCIUM CARBONATE CRYSTALS)
OTOLITHIC MEMBRANE- GELATINOUS LAYER
HAIR CELLS
NERVE CELLS
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THE UTRICLE SACCULUS
HEAD MOVEMENT
OTOCONIA (CALCIUM CARBONATE CRYSTALS)
OTOLITHIC MEMBRANE- GELATINOUS LAYER
HAIR CELLS
NERVE CELLS
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THE VESTIBULAR APPARATUS SEMICIRCULAR CANALS
ONE CANAL IN EACH COORDINATE PLANE
UTRICLE SACCULUS
AMPULLA
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THE AMPULLA
HAIR CELLS
NERVE CELLS
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THE AMPULLA
MOVEMENT OF HEAD
INERTIAL FLUID MOVEMENT
HAIR CELLS BENT
NERVE CELLS FIRE
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TASTE SENSATION

• GUSTATORY RECEPTORS
• GUSTATORY PATHWAYS

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GUSTATORY RECEPTORS

• TASTE BUDS ON TONGUE LOCALIZED
• SWEET TIP
• BITTERBACK
• SOUR SIDES
• SALT FRONT

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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

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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

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THE AUTONOMIC NERVOUS SYSTEM

• TWO NEURON CHAINS
• SYMPATHETIC
• PARASYMATHETIC

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TWO NEURON CHAINS
PRESYNAPTIC NEURON
EFFECTOR ORGAN
SPINE
POSTSYNAPTIC NEURON
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SYMPATHETIC

• GANGLION NEAR SPINE
• SHORT PREGANGLIONIC NEURONS
• LONG POSTGANGLIONIC NEURONS
• FLIGHT OR FIGHT
• POSTGANGLIONIC NEURONS ARE ADRENERGIC

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PARASYMPATHETIC

• GANGLION NEAR EFFECTOR ORGAN
• LONG PREGANGLIONIC NEURONS
• SHORT POSTGANGLIONIC NEURONS
• COUCH POTATO
• POSTGANGLIONIC NEURONS ARE CHOLINERGIC

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EFFECTS OF ANS