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Pain Physiology
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Pain Physiology
See Also
Chronic Pain
Pathophysiology
Pain Perception Factors
Response to
Chronic Pain
may be learned
Reaction to pain may be reinforced (patient, family)
Behavior may persist after pain resolves
Modulation of sensation
First dorsal horn
Synapse
enhances or inhibits pain
Modulation occurs in various locations
Spinothalamic Tract
Frontal cortex
Descending inhibitory neuro-systems
Pain Mechanisms
Neuropathic pain
Characteristics: Burning, stabbing or shooting pain
Examples: Stroke, Radiculopathy
Musculoskeletal pain or Mechanical compression pain
Characteristics: Aching, soreness, stiffness
Examples:
Myofascial Pain Syndrome
,
Fibromyalgia
,
Low Back Pain
Inflammatory pain
Characteristics: Aching, swelling, hot, red
Examples:
Rheumatoid Arthritis
, Postoperative pain,
Septic Joint
Dorsal horn
Synapse
physiology
Neurotrasmitters transmitting pain signals from C-polynodal Nociceptor (presynaptic)
Glutamate
Dense core vessicles contain Substance P, CGRI, CCK, BDNF
Receptors on post-synaptic membrane of dorsal horn
Neuron
AMPA receptors (nociceptive pain)
Responds to acute physiologic pain
Bind glutamate
Respond to
Morphine
NK-1 and
NMDA
receptors
Responds to chronic pathologic pain (non-nociceptive pain)
Bind Substance P, CGRI, CCK, BDNF from dense core vessicles
Poor response to
Morphine
Pathophysiology
Gate Control Theory
Specific pain fibers from injured tissues via
Alpha fibers myelinated
Delta and C-fibers unmyelinated
Modulated at spinal cord gate
Substantia gelatinosa
Control transmission cells
Spinothalamic Tract
cephalad
Descending signals (regulate gate at spinal cord)
Pain transmission can be blocked by emotion or mood
Sensory discriminative system
Determines differences in sensory threshold
Motivational Affective System
Reciprocal relationship between mood and pain
Central control processes
Include unknown processes of pain
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