II. 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
- Neuropathic pain
- 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
- Neurotrasmitters transmitting pain signals from C-polynodal Nociceptor (presynaptic)
III. 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