Pathophysiology Of Pain
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|Four types of sensory neurons and their receptor cells. Nociceptors shown as free nerve endings type A|
A nociceptor (“pain receptor” from Latin nocere ‘to harm or hurt’) is a sensory neuron that responds to damaging or potentially damaging stimuli by sending “possible threat” signals to the spinal cord and the brain. The brain creates the sensation of pain to direct attention to the body part, so the threat can be mitigated; this process is called nociception,
What is the pathophysiology of pain in nursing?
Abstract – The pathophysiology of pain is a complex process that varies according to duration (eg, acute, chronic) or type (eg, nociceptive, neuropathic, psychogenic). Perioperative nurses should understand the pathways that lead to pain to better assist in managing patients’ pain symptoms.
Approaching pain from a patient-centered stance includes acknowledging that pain is defined entirely by the subjective experience of the patient, which may not be proportional with the level of tissue damage. This article provides a brief description of the pathophysiology of pain and the components of nociceptive and neuropathic pain pathways to aid the perioperative nurse in pain management.
Les Rodriguez, MSN, MPH, RN, ACNS-BC, APRN is a pain management clinical nurse specialist at AC Medical Management Clinics, Fort Worth, TX. Mr Rodriguez has no declared affiliation that could be perceived as posing a potential conflict of interest in the publication of this article.
What are the 4 physiological processes of pain?
Nociceptive Reception and Transmission Nociceptive pain occurs as a result of the activation of the peripheral nervous system by noxious stimuli, such as inflammation caused by peripheral injury or disease.37 Mersky H, Bogduk N. Part III: Pain Terms, A Current List with Definitions and Notes on Usage.
IASP Task Force on Taxonomy.2017. p8. The four steps of pain signaling and processing The neurophysiologic underpinnings of pain can be divided into four stages: transduction, transmission, pain modulation, and perception.38 National Pharmaceutical Council and Joint Commission on Accreditation of Healthcare Organizations.
Pain: Current Understanding of Assessment, Management, and Treatments. Reston, VA: National Pharmaceutical Council; 2001. p10 At every point in the process, the intensity and propagation of pain signals can be either inhibited or facilitated by neural pathways.
- This capacity to modulate signaling may account, in part, for wide variations in pain perception between different individuals who sustain the same injury.39 Ossipov MH.
- The Perception and Endogenous Modulation of Pain.
- Scientifica.2012. p1-2.
- Transduction Transduction occurs when a stimulus, such as pressure, thermal energy, or chemical irritation, is converted into a nerve signal or action potential.
This occurs at the ends of sensory nerve cells known as nociceptors whose terminals are sensitive to this type of activation.40 National Pharmaceutical Council and Joint Commission on Accreditation of Healthcare Organizations. Pain: Current Understanding of Assessment, Management, and Treatments.
Reston, VA: National Pharmaceutical Council; 2001. p4. Transmission Transmission is the process of transferring pain information from the peripheral to the central nervous system.41 National Pharmaceutical Council and Joint Commission on Accreditation of Healthcare Organizations. Pain: Current Understanding of Assessment, Management, and Treatments.
Reston, VA: National Pharmaceutical Council; 2001. P6 Signals are transmitted along the axons of nociceptors. Primary nociceptive sensory nerve fibers, synapse with second-order neurons in the dorsal horn of the spinal cord. From here, neurons project to the brainstem, thalamus, and hypothalamus, as well as to reflex arcs to mediate an avoidance response.42 Buschmann H et al.
- P5 Modulation Pain modulation refers to up or down regulation of pain signals throughout the spinal cord and the brain.43 Hudspith MJ, Siddall PJ, Munglani R.
- Physiology of pain.
- In: Hemming HC, Hopkins PM, eds.
- Foundations of Anesthesia.2nd ed.
- London, UK: Mosby; 2006.
- P277 Many of these signals never reach consciousness because they are dampened by intrinsic modulatory activity within the central nervous system.
The gate control theory, advanced by Melzack and Wall, focused on descending pathways from the brain to the spinal cord that inhibited pain signaling.44 Tobaldini G. Pain Inhibits Pain: an Ascending-Descending Pain Modulation Pathway Linking Mesolimbic and Classical Descending Mechanisms.
Molecular Neurobiology.2019. p1-2 The current view is that signals originating in the brain can both inhibit and facilitate pain signal transmission.45 Wall and Melzack’s Textbook of Pain, 5th Edition.2006. p130-135. Perception Perception of pain is the awareness—typically an uncomfortable awareness—associated with a specific area of the body.47 NPC and JCAHO.
Pain: Current Understanding of Assessment, Management, and Treatments.2001. p7. It depends on the transmission of pain signals through the thalamus to the cortex and limbic system.46 Hudspith MJ, Siddall PJ, Munglani R. Physiology of pain. In: Hemming HC, Hopkins PM, eds.
- Foundations of Anesthesia.2nd ed.
- London, UK: Mosby; 2006.
- P281 At this point in pain processing, perception of the pain experience is influenced by social and environmental cues, as well as by cultural conditioning and past personal experiences.47 NPC and JCAHO.
- Pain: Current Understanding of Assessment, Management, and Treatments.2001.
What is the etiology of pain?
Etiology of pain – Etiology means cause or set of causes. Etiology of pain refers to the cause or origin of the pain, which can be classified as one of three distinct categories: nociceptive, neuropathic, and idiopathic.
What is pain theory and mechanism?
Introduction – The Gate Control Theory of Pain is a mechanism, in the spinal cord, in which pain signals can be sent up to the brain to be processed to accentuate the possible perceived pain, or attenuate it at the spinal cord itself. The ‘gate’ is the mechanism where pain signals can be let through or restricted. One of two things can happen, the gate can be ‘open’ or the gate can be ‘closed’:
- If the gate is open, pain signals can pass through and will be sent to the brain to perceive the pain.
- If the gate is closed, pain signals will be restricted from travelling up to the brain, and the sensation of pain won’t be perceived.
If someone experiences a painful (noxious) stimulus, the application of a non-noxious (soothing or light rubbing) stimulus can help activate the gate control mechanism, and reduce the pain. There are also other factors which can help facilitate the pain gate mechanism in reducing the perceived pain. These will be further outlined below.
- Gate closed
- Gate open
How do pain receptors work?
How is pain modified? – There are several points in the pain pathway where the signal can be modified. One is the dorsal horn of the spinal cord. In this area, a ‘gate’ mechanism either lets the pain signal through or blocks it from going any further. This is the basis of the gate control theory of pain described below.
|Gate control theory of pain|
|The gate control theory of pain was put forward by Ronald Melzack and Patrick Wall in 1965. They proposed that there was a ‘gate’ mechanism in the central nervous system that opened to allow pain messages through to the brain and closed to prevent them getting through. When we feel pain, such as when we touch a hot stove, sensory receptors in our skin send a message via nerve fibres (A-delta fibres and C fibres) to the spinal cord and brainstem and then onto the brain where the sensation of pain is registered, the information is processed and the pain is perceived. The gate theory says that as these pain messages come into the spinal cord and the central nervous system (before they even get to the brain), they can be amplified, turned down or even blocked out. There are many accounts of how people injured on the battlefield or in sports games don’t feel any pain from their injuries until afterwards. This has to do with the brain being busy doing other things and shutting the gate until it can pay attention to the messages. Large diameter nerve fibres (A-beta fibres) responsible for transmitting signals of touch to the brain have the ability to close the pain gate and so block signals from other smaller diameter nerve fibres which transmit pain. An example of this would be when a child falls over and hurts her knee — if she rubs her knee, the signal from that sensation of touch temporarily blocks the pain signal travelling from the injured knee to the brain.|