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PAIN AND ITS MANAGEMENT. D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY. SOMATOSENSORY CORTEX. SOMATOTOPIC ORGANIZATION MORE AREA TAKEN BY SENSITIVE REGIONS (GREATER RECEPTOR DENSITY-SMALLER RECEPTIVE FIELDS)
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PAIN AND ITS MANAGEMENT D. C. MIKULECKY PROFESSOR OF PHYSIOLOGY
SOMATOSENSORY CORTEX • SOMATOTOPIC ORGANIZATION • MORE AREA TAKEN BY SENSITIVE REGIONS (GREATER RECEPTOR DENSITY-SMALLER RECEPTIVE FIELDS) • CELLS RESPONDING TO ONE TYPE OF SENSATION IN VERTICLE COLUMNS(FOR EXAMPLE..PACINIAN CORPUSCLES IN A FINGERTIP)
THE ANTEROLATERAL PAIN AND TEMPERATURE PATHWAY • SENSORY NEURONS SYNAPSE IN SUBSTANTIA GELATINOSA • SECONDARY NEURONS CROSS MIDLINE AND ASCEND IN ATEROLATERAL COLUMN • BRANCHES GO TO THE RETICULAR FORMATION • TERMINATE IN VENTROBASAL NUCLEUS OF THALMUS • TERTIARY NEURONS GO TO SENSORY CORTEX
THE ANTEROLATERAL PATHWAY SUBSTANTIA GELITANOSA
THE SENSATION OF PAIN • FAST PAIN • SLOW PAIN • MECHANICAL PAIN • CHEMICAL PAIN • THERMAL PAIN
FAST PAIN • OCCURS IN ABOUT 0.1 SECONDS • SUBJECTIVE DESCRIPTION:SHARP, ACUTE, ELECTRIC OR PRICKING • A FIBERS SYNAPSE ON CELLS IN LAMINA I (LAMINA MARGINALIS) IN THE DORSAL HORNS • SECONDARY NEURONS CROSS AND TRAVEL THROUGH THE ANTEROLATERAL PATHWAY TO THE VENTROBASAL COMPLEX OF THE THALAMUS • TERTIARY NEURONS GO TO THE PRIMARY SENSORY CORTEX
FAST PAIN PATHWAY VENTROBASAL NUCLEUS LAMINA MARGINALIS I II IV III VI V VII SUBSTANTIA GELITANOSA ANTEROLATERAL PATHWAY IX VIII
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
SLOW PAIN PATHWAY VENTROBASAL NUCLEUS LAMINA MARGINALIS I II IV III VI V VII SUBSTANTIA GELITANOSA ANTEROLATERAL PATHWAY IX VIII
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
CLINICAL ASPECTS OF PAIN • HYPERALGESIA • THE THALAMIC SYNDROME • HERPES ZOSTER (SHINGLES) • TIC DOULOUREUX • THE BROWN-SEQUARD SYNDROME • HEADACHE
HYPERALGESIA • ENHANCED SENSITIVITY AROUND DAMAGED TISSUE • SENSITIZATION OF NOCICEPTORS BY SUBSTANCES RELEASED WHEN TISSUE IS DAMAGED
THE THALAMIC SYNDROME • LESION OF SOMATOSENSORY THALMUS • USUALLY A DISTORTED AND EXAGERATED SUBJECTIVE QUALITY • MAY CUT OFF PAIN TRASMISSION FROM PERIPHERY
HERPES ZOSTER (SHINGLES) • USUALLY AFFECTS THE DORSAL ROOT • ONE DERMATOME AND ONE SIDE
TIC DOULOUREUX • CHRONIC NEURALGIA OF TRIGEMINAL NERVE • SOMETIMES DUE TO INFLAMMATION (NEURITIS) • SOMETIMES TREATED SURGICALLY, BUT OFTEN RETURNS
THE BROWN-SEQUARD SYNDROME • CHARACTERISTIC PATTERN OF SENSORY LOSS DUE TO LOCALIZED DAMAGE ON ONE SIDE OF SPINE • USUALLY ACCOMPANIED BY MOTOR LOSS AS WELL
LESION ON RIGHT HALF OF SPINAL CORD • LOSS OF PAIN SENSATION ON LEFT SIDE BELOW LESION • LOSS OF TOUCH AND VIBRATION ON RIGHT SIDE BELOW LESION • LOSS OF BOTH ON RIGHT SIDE AT SAME LEVEL • NO LOSS ABOVE LESION
HEADACHE • SELDOM DUE TO BRAIN DAMAGE • NO SENSORY NERVES IN BRAIN LIKE THERE ARE IN PERIPHERY • TENSION INDUCED MUSCLE TIGHTNESS • SWELLING OF THE MUCOUS MEMBRANES • EYE DISORDERS • DILATION OF CEREBRAL BLOOD VESSELS • INCREASED INTERCRANIAL PRESSURE • INFLAMMATION AND SWELLING