Barker Patho of Pain Flashcards
What are examples of acute pain?
-Injury
-post-operative flare
When can pain be considered chronic pain?
When it lasts for more than 3 months
What are the types of chronic pain?
-Nociceptive (somatic)
-Central neuropathic
-Peripheral neuropathic
-Visceral
-Mixed
Which types of pain are considered inflammatory pain?
-Nociceptive (somatic)
-Visceral
Examples of nociceptive (somatic) pain
-Osteoarthritis
-Rheumatoid arthritis
-Osteosarcoma
-Skin/deep tissue
Examples of central neuropathic pain
-Post-stroke
-Multiple sclerosis
-Spinal cord injury
-Migraine
-HIV related neuropathic pain
Examples of peripheral neuropathic pain
-Post-herpetic neuralgia
-Diabetic neuropathy
Examples of visceral pain
-Internal organ
-Pancreatitis
-Inflammatory bowel syndrome
Examples of mixed pain
-Lower back
-Cancer
-Fibromyalgia
Functions of pain
-Warning system
-Aid in repair (hypersensitivity)
-Can be maladaptive
Temporal features of pain
-Onset
-Duration
-Course
-Pattern
How is inflammatory pain described?
Throbbing or pulsating
How is neuropathic pain described?
Stabbing, shooting, burning or tingling
How is visceral pain described?
Squeezing
Why does pain impact mood?
Pain is an emotion
How does pain travel through the nervous system?
-Pain travels from the site of trauma in the periphery to the spinal cord through peripheral nerves, to the dorsal root ganglia, then to the dorsal horn of the spinal cord
-The spinal cord then sends signals to the brain via the spinothalamic tract. This signal is referred to as the ascending input
-The brain then sends a signal back down to the spinal cord to activate reflex responses in the periphery. This signal is known as the descending modulation
Which receptors are the temperature sensitive receptors?
-Transient receptor potential cation channel (TRP)
-TRPV (vanilloid) = heat
-TRPM (melastatin) = cold
Which receptors are the acid-sensitive receptors?
Acid-sensing ion channel (ASIC) = activated by H+ and conducts Na+
Which receptors are pressure sensing receptors?
-MDEG
-DRASIC
-TREK-1
Chemicals in the body that cause pain
-Histamine
-Bradykinin
Which nerve brings pain signals from the skin to the spinal cord?
Afferent nerve
Which nerve brings pain signals from the spinal cord to the muscle to generate a reflex response?
Efferent nerve
Which receptors are activated in the synapse of the spinal cord to send signals to the brain or periphery?
-AMPA
-mGluR
-NMDAR
Which chemical activates receptors in the spinal cord?
Glutamate
Which three pain fibers transduce pain signals to the spinal cord?
-Abeta-fibers
-Adelta-fibers
-C-fibers
What kind of feelings do the Abeta-fibers produce?
-Does not produce pain (non-noxious)
-Involved with feelings of touch and pressure
Where do Abeta-fibers innervate?
The skin
Three different pain fibers ranked by fastest to slowest
Abeta-fibers > Adelta-fibers(first pain) > C-fibers(second pain)
What kind of feelings do the Adelta-fibers produce?
-Pain and cold
-Sharp and prickly
What kind of feelings do the C-fibers produce?
-Pain
-Temp
-Touch
-Pressure
-Itch
-Dull and aching
Why do the three pain fibers differ in speed?
C-fibers are unmyelinated while the two A-fibers are myelinated with Abeta having a thick myelin sheathe
What is peripheral sensitization?
-Repeated stimuli reduce firing threshold
-Repeated stimuli release a substance called substance P
-Substance P increases expression of pain receptors resulting in sensitization
What effects does substance P have on the body?
-Vasodilation
-Degranulation of mast cells
-Release of histamine
-Inflammation and prostaglandins
What causes sensitization of neuropathic pain?
Increased AMPA and NMDA expression and sensitivity in the spinal synapse
What contributes to spontaneous dysesthesias (shooting, burning pain) in neuropathic pain sensitization?
-Spontaneous afferent activity
-Spinal sensitization
What contributes to allodynia (light touch hurts) in neuropathic pain sensitization?
-Spinal sensitization
-Abeta afferent fibers
What causes spontaneous afferent activity?
Possibly enhanced expression of sodium channel subtypes contributing to:
-Enhanced cellular excitability
-Generation of ectopic action potentials (action potentials can occur spontaneously)
What causes spinal sensitization?
-Release of neuropeptides which bind to NK1 and CGRP-R
-These receptors lead to an increase in intracellular PLC which increases PKC inside the cell
-PKC increases expression of AMPA and NMDA receptors which enhances the conduction of pain
Which pathway in the brain has a high expression of opioid receptors?
Descending pathway
What are the effects of the expression of Mu opioid receptors on the brain?
-Alter mood
-Produce sedation
-Reduce emotional reaction
What are the effects of the expression of Mu opioid receptors on the brainstem?
Increase activity of descending fibers
What are the effects of the expression of Mu opioid receptors on the spinal cord?
-Inhibit vesicle release
-Hyperpolarize post-synaptic membrane
What are the effects of the expression of Mu opioid receptors on the periphery?
-Reduce activation of primary afferent
-Modulate immune activity
