Podcast
Questions and Answers
Which of the following neurotransmitters is involved in the release of enkephalin in the spinal cord?
Which of the following neurotransmitters is involved in the release of enkephalin in the spinal cord?
What is the primary function of the periaqueductal gray and periventricular areas of the mesencephalon and pons in pain modulation?
What is the primary function of the periaqueductal gray and periventricular areas of the mesencephalon and pons in pain modulation?
Which of the following mechanisms does NOT contribute to the analgesic effects of opioids?
Which of the following mechanisms does NOT contribute to the analgesic effects of opioids?
Which of the following is an example of exogenous opioid peptides?
Which of the following is an example of exogenous opioid peptides?
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What is the primary mechanism by which the 'gate control theory' explains pain modulation?
What is the primary mechanism by which the 'gate control theory' explains pain modulation?
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The 'gate' in the gate control theory is located in which part of the spinal cord?
The 'gate' in the gate control theory is located in which part of the spinal cord?
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Which of these methods of pain relief is NOT directly related to the gate control theory?
Which of these methods of pain relief is NOT directly related to the gate control theory?
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Which type of neuron, when stimulated, is responsible for closing the 'gate' to pain signals according to the gate control theory?
Which type of neuron, when stimulated, is responsible for closing the 'gate' to pain signals according to the gate control theory?
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What neurotransmitter is associated with chronic pain in the paleospinothalamic pathway?
What neurotransmitter is associated with chronic pain in the paleospinothalamic pathway?
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Which of the following is NOT a characteristic of the paleospinothalamic pathway?
Which of the following is NOT a characteristic of the paleospinothalamic pathway?
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Where does the second-order neuron of the paleospinothalamic pathway travel?
Where does the second-order neuron of the paleospinothalamic pathway travel?
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Which of the following statements accurately describes referred pain?
Which of the following statements accurately describes referred pain?
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Which of the following is an example of referred pain?
Which of the following is an example of referred pain?
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What is the central concept behind the convergence theory of referred pain?
What is the central concept behind the convergence theory of referred pain?
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According to the facilitatory theory of referred pain, how do visceral and somatic pain afferents interact?
According to the facilitatory theory of referred pain, how do visceral and somatic pain afferents interact?
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Which of the following statements accurately describes the role of the substantia gelatinosa in both the paleospinothalamic pathway and referred pain?
Which of the following statements accurately describes the role of the substantia gelatinosa in both the paleospinothalamic pathway and referred pain?
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What is the primary function of the thalamus in pain perception?
What is the primary function of the thalamus in pain perception?
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What is transduction in the context of pain physiology?
What is transduction in the context of pain physiology?
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Which type of nerve fibers is involved in the transmission of pain impulses?
Which type of nerve fibers is involved in the transmission of pain impulses?
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How does pain modulation occur in the central nervous system?
How does pain modulation occur in the central nervous system?
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What can result from a lesion of the thalamus regarding pain perception?
What can result from a lesion of the thalamus regarding pain perception?
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What is the role of Aβ sensory fibers in relation to pain sensation?
What is the role of Aβ sensory fibers in relation to pain sensation?
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Which type of pain is characterized by its origin from a lesion or disease of the somatosensory nervous system?
Which type of pain is characterized by its origin from a lesion or disease of the somatosensory nervous system?
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How do somatic inputs from the face and oral structures enter the nervous system?
How do somatic inputs from the face and oral structures enter the nervous system?
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What is a basic clinical feature of dental pain of pulpal origin?
What is a basic clinical feature of dental pain of pulpal origin?
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What type of pain is associated with discomfort during biting due to occlusal pressure?
What type of pain is associated with discomfort during biting due to occlusal pressure?
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What is psychogenic pain primarily influenced by?
What is psychogenic pain primarily influenced by?
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How does rubbing the skin near painful areas help relieve pain?
How does rubbing the skin near painful areas help relieve pain?
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What characterizes phantom pain?
What characterizes phantom pain?
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Which of the following is NOT a characteristic of fast pain?
Which of the following is NOT a characteristic of fast pain?
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What type of nerve fiber transmits slow pain signals?
What type of nerve fiber transmits slow pain signals?
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Which of these is NOT a sign associated with pain?
Which of these is NOT a sign associated with pain?
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Which of the following statements is TRUE regarding pain receptors?
Which of the following statements is TRUE regarding pain receptors?
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Which of these are examples of potential pain receptor locations?
Which of these are examples of potential pain receptor locations?
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What is the primary function of pain?
What is the primary function of pain?
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What statement aligns with the definition of pain by the International Association for the Study of Pain (IASP)?
What statement aligns with the definition of pain by the International Association for the Study of Pain (IASP)?
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Which of the following is NOT a factor that can modify pain perception?
Which of the following is NOT a factor that can modify pain perception?
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What is the primary neurotransmitter secreted by the Aδ fibers in the spinal cord?
What is the primary neurotransmitter secreted by the Aδ fibers in the spinal cord?
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Which of the following chemicals is NOT a direct stimulator of nociceptors?
Which of the following chemicals is NOT a direct stimulator of nociceptors?
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Which type of pain involves the neospinothalamic pathway?
Which type of pain involves the neospinothalamic pathway?
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What is the most likely cause of pain following tissue damage?
What is the most likely cause of pain following tissue damage?
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What type of pain is characterized by progressive excitation of pain fibers with continued stimulation, even after the stimulus is removed?
What type of pain is characterized by progressive excitation of pain fibers with continued stimulation, even after the stimulus is removed?
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Which of the following stimuli is NOT associated with slow pain?
Which of the following stimuli is NOT associated with slow pain?
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Which of the following is a characteristic of the neospinothalamic tract?
Which of the following is a characteristic of the neospinothalamic tract?
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What is the primary reason for pain associated with muscle spasms?
What is the primary reason for pain associated with muscle spasms?
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What is the mechanism responsible for the increased intensity of pain associated with tissue ischemia?
What is the mechanism responsible for the increased intensity of pain associated with tissue ischemia?
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Which of the following statements about pain receptors is TRUE?
Which of the following statements about pain receptors is TRUE?
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Study Notes
Pain Overview
- Pain is an unpleasant sensory and emotional experience.
- Nociception is the neural response to potentially tissue-damaging stimuli.
- Pain is a symptom, protective, and modified by factors like development, behavior, personality, and culture.
- Associated signs of pain include crying, sweating, increased heart rate and blood pressure, and behavioral changes.
Types of Pain
- Fast pain (e.g., sharp, pricking, acute): felt within 0.1 seconds of stimulus, well-localized, not felt in deeper tissues.
- Slow pain (e.g., burning, aching, throbbing, chronic): felt after 1 second or more, increases slowly, poorly localized, usually associated with tissue damage, can cause prolonged and almost unbearable suffering.
Pain Receptors
- Pain receptors are free nerve endings.
- Widespread in superficial skin layers and internal tissues (excluding brain and lung parenchyma).
- Examples include periosteum, arterial walls, and joint surfaces.
- Types of stimuli include mechanical, thermal, and chemical.
- Fast pain is elicited by mechanical and thermal stimuli.
- Slow pain is elicited by all three types of stimuli.
- Chemicals like bradykinin, serotonin, potassium ions, histamine, hydrogen ions (H+), lactic acids, acetylcholine (ACh), proteolytic enzymes, leukotrienes, and cytokines contribute to pain.
- Prostaglandins and substance P increase nociceptor sensitivity to other stimuli.
Pain Receptors and Stimulation
- Pain receptors do not immediately adapt.
- As pain stimulus continues, the excitation of pain fibers increases and pain receptor sensitivity increases (hyperalgesia).
- The rate of tissue damage correlates with the intensity and rate of pain.
Cause of Pain
- Tissue damage: Bradykinin is believed to be the main contributor, with pain intensity correlating with increased potassium ion concentration and proteolytic enzymes.
- Ischemia: Blocked blood flow results in tissue pain, with pain occurring more quickly with increased metabolism and lactic acid buildup.
- Muscle spasm: This contributes to pain by directly stimulating mechanosensitive receptors and indirectly by compressing blood vessels, causing ischemia.
Dual Pain Pathways
- Neospinothalamic tract: transmits fast, acute pain (Aδ fibers)
- First-order neurons terminate in lamina I, then excite second-order neurons.
- Glutamate is the neurotransmitter.
- Second-order neurons decussate to the opposite side through the anterior commissure and travel up the lateral spinothalamic tract.
- Most fibers terminate in the thalamus, some in the brainstem reticular formation and somatosensory cortex.
- Fast pain is localized more exactly.
- Paleospinothalamic tract: transmits slow, chronic pain (C fibers)
- First-order neurons synapse in laminae II and III, neurotransmitter is substance P.
- Second-order neurons cross to the opposite side and travel up the lateral spinothalamic tracts.
- Fibers terminate in the thalamus and reticular nuclei, tectal area, and periaqueductal gray, then to somatosensory cortex.
Pain Perception
- Thalamus is an important center.
- Lesions produce "thalamic pain".
- Sensory cortex is crucial for localization and intensity.
- Other areas include reticular formation, limbic areas, and hypothalamus.
Process of Pain Physiology
- Transduction: noxious stimuli converted to electrical energy (transduction).
- Transmission: impulses conveyed by Aδ or C fibers through the spinothalamic tract.
- Perception: nociceptive input reaches cortex (complex interaction in neurons)
- Modulation: CNS ability to control pain transmission (inhibition using endogenous opioids).
Pain Modulation/Modification
- Pain modulation refers to variability in pain perception.
- Endogenous and exogenous mechanisms influence pain thresholds, increasing/decreasing.
- Enhancement/inhibition occurs at all levels of the nervous system (peripheral nerve, spinal cord, brain).
Pain Modulation (Pain Suppression)
- Analgesia system blocks pain signals.
- Includes periaqueductal gray, periventricular areas of mesencephalon and pons, raphe magnus nucleus, nucleus reticularis.
- Transmitters like enkephalin and serotonin cause pre- and post-synaptic inhibition of incoming pain fibers and release enkephalin.
- Brain's opioid system (endorphins, enkephalins, dynorphins) plays a role.
Opioid Actions
- Endogenous opioids (endorphins, enkephalins, dynorphins) and exogenous opioids (morphine, codeine, fentanyl, pethidine, opium, heroin) act presynaptically or postsynaptically.
- They block calcium channels, inhibit calcium influx preventing the release of pain neurotransmitters.
- They open potassium channels, which leads to membrane hyperpolarization and inhibits pain neurotransmitter activity.
- They activate the descending inhibitory pathway.
- They inhibit GABA-mediated inhibition.
Pain Modulation (Gate Control Theory)
- Non-painful input closes gates to painful input.
- Substantia gelatinosa (SG) in the dorsal horn acts as a gate, only allowing specific impulses to pass.
- SG activation is triggered (Aβ neurons stimulated). This closes the gate to Ad and C fibers.
- Ad and C fiber stimulation blocks the gate allowing Aβ fibers to be triggered.
- Methods employing this theory for pain relief include massage, applying irritants, transcutaneous electrical nerve stimulation, and acupuncture.
Varieties of Pain
- Phantom pain: felt without stimulus due to injured nerve ending abnormal action potential (e.g., amputated limb).
- Psychogenic pain: felt, but cause is emotional, not physical
- Neuropathic pain: caused by lesion or disease somatic sensory nervous system, (e.g., diabetes neuropathy).
Pain in Dentistry
- A-delta fibers are stimulated by air, cold, heat, and drilling, resulting in fast, sharp, well- localized pain.
- C-fibers are stimulated by inflammatory mediators, mechanical deformation, heat, resulting from slower, dull, lingering, poorly localized pain.
Orofacial Pain Pathway
- Somatic input from the face and oral structures uses the trigeminal nerve (CN V) to reach the spinal cord. This nerve and its pathway differs from nerves for other areas.
Dental Pain of Pulp Origin
- Visceral in character, threshold-based, responds to noxious stimuli, but not usually to masticatory function.
- Not localized at first.
- Becomes chronic or spreads to periodontal ligament structures.
Dental Pain of PDL Origin
- Deep somatic pain, localized.
- Related to biomechanical function(masticatory).
- Receptors are capable of precise localization.
- Characterized by biting discomfort under occlusal pressure.
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Description
Explore the complexities of pain, including its definition as an unpleasant sensory and emotional experience. Learn about the types of pain, from sharp and acute to burning and chronic, as well as the pain receptors responsible for detecting harmful stimuli.
