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![ 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
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.](https://image.slidesharecdn.com/theoriesofpain-190625035203/75/Theories-of-pain-4-2048.jpg)
![ 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.](https://image.slidesharecdn.com/theoriesofpain-190625035203/75/Theories-of-pain-7-2048.jpg)
Uploaded byAlisha Talwar
Theories of pain
The document discusses several theoretical frameworks that have been proposed to explain pain perception physiology. It outlines several theories including: the intensity/summation theory which defines pain as an emotion from excessive stimulation; the specificity theory which proposes pain receptors transmit signals to a pain center in the brain; and the pattern theory which suggests pain results from certain patterns of neural activity. It also describes Melzack and Wall's gate control theory, which proposes that large diameter fibers can open or close a 'gate' in the spinal cord to pain signal transmission from small fibers to the brain.
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Various theoretical frameworks exist that address the physiological basis of pain perception.
Defines pain as an emotion linked to strong stimuli, with key factors being stimulus intensity and central summation.
Describes pain as an independent sensation from specialized nociceptors transmitting signals to the brain.
Pain includes both the noxious stimulus and the psychological reaction it provokes.
Pain perception results from specific patterns of neural firing from shared receptors responding to different stimuli.
Pain and non-pain experiences arise from different neural patterns, where intense stimulation induces pain.
Damage activates fibers leading to abnormal spinal circuits, resulting in constant pain signals to the brain.
Pain involves both perception and reactive processes influenced by cognitive and cultural factors.
Describes two pain transmission systems: fast for somatic afferents, and slow allowing for inhibition.
Small, slow fibers (T-cells) convey pain signals from the spinal cord to the brain and interact with larger fibers.
Large fibers potentially block smaller fiber signals, creating a 'gate' affecting pain sensation.
Three main factors influence the pain gate: activity in pain fibers, other peripheral fibers, and descending brain messages.
Active pain fibers open the gate, while A-beta fibers from harmless stimuli tend to close it, reducing pain.
Brain signals can open or close the gate for pain, explaining variations in pain perception due to different mental states.
The SG has excitatory and inhibitory synapses with T-cells, determining the transmission or inhibition of pain signals.
Pain perception is influenced by social, psychological, and cultural factors, impacting emotions and behaviors.
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Theories of pain
- 2. Several theoreticalframeworks 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.
- 3. Referred toas the Intensity/Summation Theory 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 There must be some form of summation that occurs for the sub threshold stimuli to become unbearably painful.
- 4. One ofthe 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 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.
- 5. This theorystates that pain was an experience based on both the noxious stimulus and the psychic reaction or displeasure provoked by the sensation.
- 6. The theorystated 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 There is no separate system for perceiving pain, and the receptors for pain are shared with other senses, such as of touch It suggested that all cutaneous qualities are produced by spatial and temporal patterns of nerve impulses rather than by separate, modality specific transmission route
- 7. This theoryconsiders 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.
- 8. It proposedthat 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
- 9. It statedthat 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
- 10. It describestwo 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
- 11. pain stimulationis 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.
- 12. 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.
- 13. There are3 factors which influence the 'opening and closing' of the gate 1. The amount of activity in the pain fibers. 2. The amount of activity in other peripheral fibers 3. Messages that descend from the brain. Theory provides a physiological basis for the complex phenomenon of pain.
- 14. The amountof 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.
- 15. Messages thatdescend 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
- 18. The SGhas both excitatory and inhibitory synapses with the T cells. Three kinds of neurons send signals to the SG. Two of them (A-delta and C) are slow conducting and transmit pain signals; the third (A-beta) inhibits the transmission of pain signals. Pain Signal ---> Excites the SG+ --->Opens Gate ---> T-cells fire ---> Pain signal sent Non-painful Stimulus ---> Excites the SG - --->Closes Gate ---> T-cells inhibited ---> Reduces pain signal
- 20. It statesthat 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