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Pain and Temperature Sensing: Nociception and Thermoception

Jun 1, 2024

Pain and Temperature Sensing: Nociception and Thermoception

Key Concepts

  • Nociception: The scientific term for sensing pain.
  • Thermoception: The scientific term for sensing temperature.
  • Both senses rely on specialized receptors called TRPV1 receptors.

TRPV1 Receptors

  • Located within the cell membrane of sensory cells throughout the body.
  • Sensitive to both temperature changes and painful stimuli.
  • Activated by conformational changes in the protein structure.
  • Example: Heat or certain molecules can cause these changes.

Mechanism of Action

  1. Temperature Change

    • Example: Placing a hand on a stove induces heat.
    • Heat causes a conformational (structural) change in TRPV1 receptor protein.
    • This change activates the receptor, sending a signal to the brain.
  2. Painful Stimulus

    • Example: Sharp object poking the hand.
    • Cells break and release molecules upon injury.
    • Molecules (e.g., green molecule) bind to TRPV1 receptors, causing conformational changes.
    • Same activation process sends a pain signal to the brain.

Types of Nerve Fibers

  • A-beta fibers (Fast)

    • Large diameter, heavily myelinated.
    • Conduct signals very quickly.
    • Example: Quick hand withdrawal from hot stove.
  • A-delta fibers (Medium)

    • Medium diameter, less myelinated.
    • Conduct signals moderately fast.
    • Example: Quick pain sensation after touching a hot stove.
  • C fibers (Slow)

    • Small diameter, unmyelinated.
    • Conduct signals slowly.
    • Example: Lingering burning sensation after touching a hot stove.

Example: Jalapeno and Capsaicin

  • Eating a jalapeno triggers pain like a hot temperature.
  • Jalapeno cells contain capsaicin, which binds to TRPV1 receptors in the tongue.
  • Activates the same response as a temperature change, causing sweating and burning sensation.
  • Body reacts similarly to capsaicin as it does to heat.

Summary

  • Nociception: Sensing pain through TRPV1 receptors.
  • Thermoception: Sensing temperature through TRPV1 receptors.
  • TRPV1 receptors are activated by temperature changes and molecules like capsaicin.
  • Signal transmission to the brain involves different nerve fibers of varying speeds.