Pain and Nociceptors

Nociceptors are sensory processes that signal pain, they are found in most body tissues, including skin, bone, muscles, most internal organs, blood vessels, and heart. Basically everywhere except the brain

How do they work?

  •  When a nociceptors membrane is bent or stretched, mechanical ion gated channels open up creating action potentials.
    • Well say, can anything else activate this bad boy?
      • Certain damaged cells located at the scene of the injury that can release substances that can cause these ion channels to open, such as:
        • BRADY bunch PPALs – Bradykinin, Proteases, Potassium (k) ,ATP, and lactic acid

Logically how nociceptors work…

Let’s say a bee stings you. When the venom makes contact with your skin, it activates mast cells (found in immune system usually activated by exposure to foreign substitutes). The mast cells release histamines that bind to specific receptors on nociceptors causing membrane to depolarize. Histamines also causes blood capillaries to become leaky producing swelling and redness.

So essentially – harmful substance –> mast cells release histamines –> depolarization of membrane/leaky blood capillaries –> ouchie and bumps beestingnocic

Now let’s talk about Polymodal Receptors

Poly – a lot  Modal – different ways  *lose translation

  • Nociceptors that respond to various  stimuli 
    • Mechanical (strong stimuli)
    • Thermal (extremes -Iceland or Arizona in the summer)
    • Some chemicals
  • Two types of pain
    • First – fast and sharp (the dreaded papercut)
    • Second – delayed, dull, longer lasting, burning sensation

Side note : Transduction of painful stimuli is done by unmyelinated C fibers and lightly myelinated Aδfibers

  • Aδ fibers
    • Mediate chemical and Thermal stimuli
    • Also registers noxious (harmful) stimulation
  • C fibers
    • Deals with chemical stimuli
    • Mediates second pain sensation
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