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Theories of pain.pptx

  1. THEORIES OF PAIN SUBMITTED BY Anmol Prashar B.Sc. Nursing 4th year (Intern) Roll no 6 Date : 28-08-2020
  2. CONTENTS  Introduction  Intensive Theory (Erb,1874)  Specificity Theory(Von Frey,1895)  Strong’s Theory (Strong,1895)  Pattern Theory  Central Summation Theory (Livingstone,1943)  The 4th Theory of Pain (Hardy,Wolf and Goodell,1940s)  Sensory Interaction Theory (Noordenbos,1959)  Gate Control Theory (Melzack and Wall,1965)  Biophysical Model of Pain  Significance in Nursing practice  References
  3. INTRODUCTION As long as humans have experienced pain, they have given explanations for its existence and sought soothing agents to dull or cease the painful sensation.Physiotherapists are often confronted by patient's experiencing pain and patient's expectations of being cured are very high. A physiotherapist's approach to pain will often depend on their knowledge and their client's perception of pain and it's causes. Several theoretical frameworks have been proposed to explain the physiological basis of pain, although none yet completely accounts for all aspects of pain perception. A number of theories have been postulated to describe mechanisms underlying pain perception. These theories date back several centuries and even millennia (Kenins 1988; Perl 2007; Rey 1995  Pain is whatever the experiencing person says it is, existing whenever the experiencing person says it does” (McCaffery, 1989)  “Pain is an unpleasant sensory and emotional experience, associated with or expressed in terms of actual or potential tissue damage” (IASP, 1989)
  4. Different Theories of Pain Intensive Theory (Erb,1874) Specificity Theory(Von Frey,1895) Strong’s Theory (Strong,1895) Pattern Theory Central Summation Theory (Livingstone,1943) The 4th Theory of Pain (Hardy,Wolf and Goodell,1940s) Sensory Interaction Theory (Noordenbos,1959) Gate Control Theory (Melzack and Wall,1965)
  5. Intensive Theory of Pain  An Intensive (or Summation) Theory of Pain (now referred to as the Intensity Theory) has been postulated at several different times throughout history.  First, conceptualized in the fourth century BCE by Plato in his oeuvre Timaeus (Plato 1998), the theory defines pain, not as a unique sensory experience but rather, as an emotion that occurs when a stimulus is stronger than usual.  This theory is based on Aristotle’s concept that pain resulted from excessive stimulation of the sense of touch. Both stimulus intensity and central summation are critical determinants of pain.  It was implied that the summation occurred in the dorsal horn cells.Arthur Goldscheider further advanced the Intensity Theory, based on an experiment performed by Bernhard Naunyn in 1859 [cited in Dallenbach (1939)].
  6.  These experiments showed that repeated tactile stimulation (below the threshold for tactile perception) produced pain in patients with syphilis who had degenerating dorsal columns. When this stimulus was presented to patients 60–600 times/s, they rapidly developed what they described as unbearable pain.  Naunyn reproduced these results in a series of experiments with different types of stimuli, including electrical stimuli. It was concluded that there must be some form of summation that occurs for the sub-threshold stimuli to become unbearably painful.
  7. Specificity Theory of Pain  Specificity theory is one of the first modern theories for pain. It holds that specific pain receptors transmit signals to a “pain center” in the brain that produces the perception of pain.  Von Frey (1895) argued that the body has a separate sensory system for perceiving pain—just as it does for hearing and vision.  This theory considers pain as an independent sensation with specialised peripheral sensory receptors [nociceptors], which respond to damage and send signals through pathways (along nerve fibres) in the nervous system to target centres in the brain.  These brain centres process the signals to produce the experience of pain. Thus, it is based on the assumption that the free nerve endings are pain receptors and that the other three types of receptors are also specific to a sensory experience
  8. Descartes' pain pathway: "Particles of heat" (A) activate a spot of skin (B) attached by a fine thread (cc) to a valve in the brain (de) where this activity opens the valve, allowing the animal spirits to flow from a cavity(F) into the muscles causing them to flinch from the stimulus, turn the head and eyes toward the affected body part, and move the hand and turn the body protectively.
  9. Strong’s Theory of Pain  Strong investigated physical pain, particularly that felt through the skin. He isolated pain from displeasure by focusing on cutaneous pain, where the infliction of pain carried no immediate threat, and therefore the emotional response was removed.  He proposed that pain was an experience based on both the noxious stimulus and the psychic reaction or displeasure provoked by the sensation.  Strong concluded that pain is the sensation: The first sensation was the experience of heat and then came the sensation of pain. He claimed that in in earlier stages of evolution sensations were merely modifications of the nervous system and it was only after the development of the ego did these sensations become projected emotions known as displeasure
  10. Pattern Theory of Pain  In an attempt to overhaul theories of somaesthesis (including pain), J. P. Nafe postulated a “quantitative theory of feeling” (1929).  This theory ignored findings of specialized nerve endings and many of the observations supporting the specificity and/or intensive theories of pain.  The theory stated that any somaesthetic sensation occurred by a specific and particular pattern of neural firing and that the spatial and temporal profile of firing of the peripheral nerves encoded the stimulus type and intensity.
  11.  Goldschneider (1920) proposed that there is no separate system for perceiving pain, and the receptors for pain are shared with other senses, such as of touch. This theory considers that peripheral sensory receptors, responding to touch, warmth and other non- damaging as well as to damaging stimuli, give rise to non-painful or painful experiences as a result of differences in the patterns [in time] of the signals sent through the nervous system.  Thus, according to this view, people feel pain when certain patterns of neural activity occur, such as when appropriate types of activity reach excessively high levels in the brain. These patterns occur only with intense stimulation. Because strong and mild stimuli of the same sense modality produce different patterns of neural activity, being hit hard feels painful, but being caressed does not. It suggested that all cutaneous qualities are produced by spatial and temporal patterns of nerve impulses rather than by separate, modality specific transmission routes.
  12. Central Summation Theory It proposed that the intense stimulation resulting from the nerve and tissue damage activates fibers that project to internuncial neuron pools within the spinal cord creating abnormal reverberating circuits with self-activating neurons.  Prolonged abnormal activity bombards cells in the spinal cord, and information is projected to the brain for pain perception
  13. The Fourth Theory of Pain It stated that pain was composed of two components: the perception of pain and the reaction one has towards it. The reaction was described as a complex physiopsychological process involving cognition, past experience, culture and various psychological factors which influence pain perception.
  14. Sensory Interaction Theory It describes two systems involving transmission of pain: fast and slow system. The later presumed to conduct somatic and visceral afferents whereas the former was considered to inhibit transmission of the small fibers
  15. Gate Control Theory  Melzack has proposed a theory of pain that has stimulated considerable interest and debate and has certainly been a vast improvement on the early theories of pain.  According to his theory, pain stimulation is carried by small, slow fibers that enter the dorsal horn of the spinal cord; then other cells transmit the impulses from the spinal cord up to the brain. These fibers are called T-cells. The T-cells can be located in a specific area of the spinal cord, known as the substantial gelatinosa. These fibers can have an impact on the smaller fibers that carry the pain stimulation. In some cases they can inhibit the communication of stimulation, while in other cases they can allow stimulation to be communicated into the central nervous system.
  16.  For example, large fibers can prohibit the impulses from the small fibers from ever communicating with the brain. In this way, the large fibers create a hypothetical "gate" that can open or close the system to pain stimulation.  According to the theory, the gate can sometimes be overwhelmed by a large number of small activated fibers. In other words, the greater the level of pain stimulation, the less adequate the gate in blocking the communication of this information.
  17. There are 3 factors which influence the ‘opening and closing’ of the gate : The amount of activity in the pain fibers. Activity in these fibers tends to open the gate. The stronger the noxious stimulation, the more active the pain fibers. The amount of activity in other peripheral fibers—that is, those fibers that carry information about harmless stimuli or mild irritation, such as touching, rubbing, or lightly scratching the skin. These are large- diameter fibers called A-beta fibers. Activity in A-beta fibers tends to close the gate, inhibiting the perception of pain when noxious stimulation exists. This would explain why gently massaging or applying heat to sore muscles decreases the pain.
  18.  Messages that descend from the brain. Neurons in the brainstem and cortex have efferent pathways to the spinal cord, and the impulses they send can open or close the gate. The effects of some brain processes, such as those in anxiety or excitement, probably have a general impact, opening or closing the gate for all inputs from any areas of the body. But the impact of other brain processes may be very specific, applying to only some inputs from certain parts of the body. The idea that brain impulses influence the gating mechanism helps to explain why people who are hypnotized or distracted by competing environmental stimuli may not notice the pain of an injury.
  19. In the top panel, the nonnociceptive, large-diameter sensory fiber (orange) is more active than the nociceptive small-diameter fiber (blue), therefore the net input to the inhibitory interneuron (red) is net positive. The inhibitory interneuron provides presynaptic inhibition to both the nociceptive and nonnociceptive neurons, reducing the excitation of the transmission cells. In the bottom panel, an open "gate" (free-flowing information from afferents to the transmission cells) is pictured. This occurs when there is more activity in the nociceptive small-diameter fibers (blue) than the nonnociceptive large-diameter fibers (orange). In this situation, the inhibitory interneuron is silenced, which relieves inhibition of the transmission cells. This "open gate" allows for transmission cells to be excited, and thus pain to be sensed.
  20. The benefit of this theory is that it provides a physiological basis for the complex phenomenon of pain. It does this by investigating the complex structure of the nervous system, which is comprised of the following two major divisions:  Central nervous system (the spinal cord and the brain)  Peripheral nervous system (nerves outside of the brain and spinal cord, including branching nerves in the torso and extremities, as well as nerves in the lumbar spine region
  21. Biopsychosocial Model of Pain The Biopsychosocial Model states that pain is not simply a neurophysiological phenomenon, but also involves social and psychological factors. It says that factors like culture, family, nociceptive stimuli and environment influence pain perception and thus ultimately affect a person’s emotions, behaviors and cognition.
  22. For example, the Sun Dance is a ritual performed by traditional groups of Native Americans. In this ritual, cuts are made into the chest of a young man. Strips of leather are slipped through the cuts, and poles are tied to the leather. This ritual lasts for hours and undoubtedly generates large amounts of nociceptive signaling, however the pain may not be perceived as noxious or even perceived at all. The ritual is designed around overcoming and transcending the effects of pain, where pain is either welcomed or simply not perceived
  23. Significance in Nursing Practice Pain is a feared but universal experience. Early pain theories focused on locating neurological pain fibers. However, when surgical interventions failed to control the pain, other explanations were sought. The interplay between practice and research has advanced our understanding and management of pain. Current pain theories explain pain as a physical, psychological and social experience. Nursing interventions that are multidimensional will have a better chance at ameliorating a patient's pain.
  24. Reference   Barron, C. J., Klaber Moffett, J. A., & Potter, M. (2007). Patient expectations of physiotherapy: Definitions, concepts, and theories. Physiotherapy Theory and Practice, 23(1), 37–46.  Moayedi M, Davis KD. Theories of pain: from specificity to gate control. J Neurophysiol 2013; 109:5-12  Massieh Moayedi, Karen D. Davis Journal of Neurophysiology Published 1 January 2013 Vol. 109 no. 1, 5-12 DOI:  Temperature and Pain Theories of Pain Perception  Strong, C. A. (1895). The psychology of pain. Psychological Review, 2(4), 329–347    Modern Ideas: The Gate Control Theory of Chronic PainfckLRBy William W. Deardorff, PhD, ABPP