in this presentation, you will learn about pain pathway its physiology and types

1. Understanding Pain Physiology
Mehmood ul Hassan
Clínical Nurse Instructor
Surgical ICU The Aga Khan University Hospital Karachi Pakistán
10/11/2019
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2. Objectives
By the end of this presentation learner will be able to
1.Describe pain and its component
2.Identify the Nociceptors and its types
3.Distinguish between A-δ Fibers and C Fibers
4.Explain how noxious stimuli converted to nerve impulses
5.Understand the conduction and transmission of pain
impulses
6.Explain the Gate theory and endogenous analgesic system
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3. What is..
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4. Pain
• An unpleasant sensory and emotional
experience associated with actual or potential
tissue damage, or described in terms of such
damage
( International Association for the Study of Pain, 2010)
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5. Pain Components
• Sensory
– Feeling of a person regarding pain like sharp, dull,
twisting, throbbing
• Affective
– Emotional reaction like anxious, depressed
• Autonomic
– Activation of sympathetic nervous system increase
heart rate
• Motor
– Movement of body parts10/11/2019
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6. Types of pain
• Nociceptive pain
– It occur due to tissue damage
• Neuropathic pain
– pain caused by damage to, or dysfunction of, the
nervous system
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7. Description of pain
• Acute pain
– that lasts for less than three months and subsides with
healing
• Persistent or chronic pain
– that lasts more than three month
• Cancer pain
– associated with a malignancy
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8. What is Pain Pathway
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9. 10/11/2019 9

10. Pain Pathway
Transduction
Conduction
Transmission
Perception
Modulation
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11. 1.Transduction
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12. Transduction
Conversion of a stimulus into a nerve impulses
Or
Energy of mechanical, thermal and chemical
noxious stimulus is converted into electrical
signals
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13. Noxious stimuli that can cause
Tissue injury
• Exogenous
– Mechanical injury (cutting, crushing or pinching)
– Thermal injury (extreme heat, steam)
– Chemical injury (acid, )
• Endogenous
– Hypoxia, Ischemia, Infection, Dehydration,
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14. Response of tissue after injury
• Damage cell release
– Prostaglandin (Pain mediator)
• Platelets Release
– Serotonin
• Plasma release
– Bradykinin (pain mediator, vasodilator)
• Mast Cell
– Histamine (vasodilator)
• Nerve efferent
– Substance P ( pain mediated via peripheral receptors)
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15. Nociceptors
Sensory neuron that responds to noxious stimuli
and send signals to the spinal cord and brain.
Mechanical Nociceptors
Respond to Cutting, Crushing or Pinching
Thermal Nociceptors
Respond to extreme temperature especially heat
Polymodal Nociceptors
Respond to all kind of damaging stimuli10/11/2019 15

16. Nociceptors
Nociceptors
Cell body
Myelin
sheath
Principles Of Anatomy And Physiology, 12th Edition, (p. 420)
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17. Nociceptors location
• They are found in any area of the body that can
sense noxious stimuli either externally or
internally such as skin, tissue, muscle, joint,
bladder, gut and continuing along the digestive
tract.
• They are less present in deep organ
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18. Nociceptors in Tissue
Principles Of Anatomy And Physiology, 12th Edition (p. 573)
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19. Afferent Nerve Fibers
(Sensory Neuron)
• A-δ Fibers (Fast pain fibers)
– large diameter 2-5 um, myelinated fibers
– Respond to thermal, chemical and mechanical
damage
– Conduct nerve impulses at rate of 30 m/sec.
• C Fibers (Slow pain pathway)
– Small diameter 0.3-1.3, unmyelinated fibers
– Respond to polymodal nociceptor irritation
– Conduct nerve impulses slowly at rate of 12 m/sec
or less.
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20. Afferent Nerve Fibers
(Sensory Neuron)
• AB fiber (non pain fiber)
– Respond to touch and pressure
– Highly myelinated
– Vary large diameter 5-15 um
– High speed conduction velocity 30-70 m/s
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21. Afferent Pain Nerve Fibers
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22. Characteristics of Pain Nerve Fiber
Fast Pain Slow Pain
 Occur on the stimulation of
mechanical, chemical and
thermal nociceptors
 Carried by small, myelinated
A-delta fibers
 Producing sharp, prickling
sensation
 Easily localized
 Occur first
 Occur on stimulation of
polymodal nociceptors
 Carried by small, unmyelinated
C fibers
 Produce dull, aching, burning
sensation
 Poorly localized
 Occur second: persistent for long
time: more unpleasant10/11/2019
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23. 2. Conduction
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24. Conduction
Traveling of nerve impulses from nociceptors
to the terminal end of first order neuron in dorsal
horn.
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25. 3. Transmission
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26. Transmission
• Release of chemical from terminal ends of first
order neuron and movement of nerve impulses
from second order neuron to somatosensory
cortex
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27. Conduction & Transmission
Pathway
Spinothalamic Pathway
Trigeminothalamic Pathway
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28. Spinothalamic
Pathway
The anterolateral
pathway conveys
nerve impulses for
pain, cold, warmth,
itch, and tickle from
the limbs, trunk,
neck, and posterior
head to the cerebral
cortex.
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29. Spinothalamic Pathway Animation
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30. Trigeminothalamic
Pathway
The trigeminothalamic
pathway conveys nerve
impulses for most
somatic sensations
(tactile, thermal,
pain, and
proprioceptive) from
the face, nasal cavity,
oral cavity, and teeth to
the cerebral cortex.
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31. A web page here you can see the
Trigeminothalamic and Spinothalamic
Pathway.
http://axoncomplete.appspot.com/index.html
Trigeminothalamic Pathway
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32. 4. Perception
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33. Perception
• Sensation is the conscious or subconscious
awareness of changes in the external or
internal environment. Perception is the
conscious awareness and interpretation of
sensations and is primarily a function of the
cerebral cortex.
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34. 5. Modulation
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35. Modulation
Human body have endogenous analgesic
system who prevent the body from pain
Endogenous opioid system
Segmental inhibition (Pain gate control theory)
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36. Endogenous Opioid System
• Inhibitory neuron release endogenous opioid
like endorphin, enkepalins, and dynorphin
• These opioid attached with receptor located in
spinal cord, ventral medulla, periaqueductal
gray matter and provide relief from pain
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37. Gate Control Theory
• Melzak and Wall (1965)
• It work as Ascending Inhibition Mechanism, in
which noxious ascending pain impulses
blocked at spinal cord level.
• For example during pain we rub hand its
generate impulses that initiate the inhibition of
pain impulses.
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38. Gate Control Theory
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39. DO YOU EXAUST
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40. Pain pathway Animation
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43. References
• Brunner, L., Suddarth, D., & Smeltzer, S. (2008). Brunner &
Suddarth's textbook of medical-surgical nursing. Philadelphia:
Lippincott Williams & Wilkins
• Falk, S., Bannister, K., & Dickenson, A. (2014). Cancer pain
physiology. British Journal Of Pain, 8(4), 154-162.
doi:10.1177/2049463714545136.
• Basbaum, A., & Bushnell, M. (2009). Science of pain. Oxford:
Elsevier/Academic Press.
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