Pathway 13-6-2 The Trigeminal System - 3 STEPS AND MECHANISMS IN PAIN PERCEPTION
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Pathway 13-6-2 The Trigeminal System - 3 STEPS AND MECHANISMS IN PAIN PERCEPTION

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Questions and Answers

What initiates the transmission of pain signals to the central nervous system?

  • Stimulation of nerve endings by a sufficient stimulus (correct)
  • Activation of endorphin release
  • Direct signaling from the brain
  • Inhibition of inflammatory mediators

    • In the pain perception process, which structure primarily ⭐️processes⭐️ input AFTER it is detected in the periphery?

  • Cerebral cortex
  • Medullary spinal cord (correct)
  • Thalamus
  • Peripheral nerve endings

    • Which of the following best describes the complexity of pain perception?

  • It is a simple pathway response to stimuli intensity.
  • It is only dependent on the peripheral nerve endings.
  • It involves multiple levels of processing prior to perception. (correct)
  • It is solely processed in the higher brain regions.

    • Which region of the brain is primarily responsible for the final perception of pain?

    <p>Cerebral cortex</p> Signup and view all the answers

    What role do endogenous and exogenous modifications play in pain perception?

    <p>They can modify pain signals prior to perception.</p> Signup and view all the answers

    What is the initial response of nerve endings in tissue used for?

    <p>To detect tissue-damaging stimuli</p> Signup and view all the answers

    What is true about the relationship between A-delta and C fibers in the tooth pulp?

    <p>C fibers conduct pain signals and outnumber A-delta fibers.</p> Signup and view all the answers

    What role do postganglionic sympathetic efferents play in relation to nociceptors?

    <p>They regulate peripheral blood flow and can influence nociceptor activity.</p> Signup and view all the answers

    Which type of stimulus initially generates action potentials in the nociceptors?

    <p>Noxious stimuli by opening voltage-gated sodium channels.</p> Signup and view all the answers

    What characteristic is shared by nociceptor fibers in terms of myelination?

    <p>C fibers are unmyelinated while A-delta fibers are myelinated.</p> Signup and view all the answers

    Which neurotransmitter is primarily released during the depolarization of nociceptors?

    <p>Substance P.</p> Signup and view all the answers

    How does inflammation influence pain localization in periodontal tissues?

    <p>It triggers the A-Beta fibers found in PDL.</p> Signup and view all the answers

    What is the purpose of antidromic signaling in the context of nociception?

    <p>To release neurotransmitters that affect adjacent tissues.</p> Signup and view all the answers

    Which characteristic does NOT describe A-alpha fibers? 注意 A的 ALPHA喔

    <p>Associated with pain transmission.</p> Signup and view all the answers

    Study Notes

    Pain Perception Pathway

    • Nerve endings in the pulp and periradicular tissues send messages to the CNS when activated by a noxious stimulus.
    • The anatomic pathway for this transmission is well-established.
    • Pain perception involves a complex, multilevel system.
    • The system begins with the detection of tissue-damaging stimuli in the periphery.
    • The message is processed at the medullary spinal cord.
    • Finally, pain is perceived in higher brain regions such as the cerebral cortex.
    • The message can be modified by endogenous and exogenous factors before perception.
    • Clinicians deal with all three levels of the pain system when diagnosing and treating odontalgia.
    • Understanding each level of the pathway allows for recognition of therapeutic opportunities and application of effective pain control methods.

    Peripheral Neurons in Pain Perception

    • The trigeminal system contains various types of peripheral neurons, including large-diameter, heavily myelinated A-alpha, A-beta, and A-Gamma-y fibers associated with motor, proprioception, touch, pressure, and muscle spindle stretch functions.
    • Smaller, less myelinated A-Delta and unmyelinated C fibers conduct information perceived as pain.
    • These two classes of pain-sensing nerve fibers, or nociceptors, are found in the tooth pulp, with a higher concentration of unmyelinated C fibers than A-delta fibers.
    • The classification system is based on the size and myelination of the neurons, not necessarily their function.
    • Another class of pulpal C fibers are postganglionic sympathetic efferents found in association with blood vessels, regulating PBF and potentially influencing the activity of peripheral nociceptors.

    Pain Perception and Localization

    • Most pulpal sensory fibers are nociceptive, with free nerve endings, leading to the perception of pure pain.
    • Pain localization is challenging due to the nature of pulpal sensory fibers.
    • Electrical stimulation can result in a prepain sensation, also difficult to localize.
    • Inflammation extending to the periodontal ligament enhances pain localization with light mechanical stimuli, such as percussion tests.

    Nociceptor Depolarization and Neurotransmitter Release

    • A noxious stimulus depolarizes nociceptors in normal uninflamed pulp and periradicular tissues.
    • Depolarization occurs through the opening of voltage-gated sodium channels (Na-V), generating action potentials.
    • Action potentials activate an antidromic response, releasing proinflammatory neuropeptides like substance P (SP), calcitonin gene-related peptide (CGRP), neurokinins, and glutamate from afferent terminals in the pulp, periradicular tissues, and neighboring teeth.

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