Physiology of Pain, Animation.

00:03:21
https://www.youtube.com/watch?v=uOaiaYDoUnA

Summary

TLDRPain is a critical defense mechanism that alerts the body to potential injury or disease. It is transmitted via nociceptors to the spinal cord and then to the brain, where it is interpreted and localized. Pain signals travel through two main pathways: the spinothalamic tract for localized pain and the spinoreticular tract for emotional aspects of pain. Visceral pain from internal organs can cause referred pain due to shared spinal pathways, making it hard for the brain to discern the origin of the pain.

Takeaways

  • 🩹 Pain warns about injuries or diseases.
  • 🧠 The brain interprets pain signals.
  • 📡 Nociceptors are the pain receptors.
  • ⚡ A fibers transmit sharp pain.
  • 🐌 C fibers transmit dull pain.
  • 🔄 Pain signals cross to the opposite side in the spinal cord.
  • 📉 Spinothalamic tract localizes pain.
  • 💭 Spinoreticular tract deals with emotional pain.
  • 🩺 Somatic pain comes from external injuries.
  • 🔗 Referred pain can mislead the perception of pain location.

Timeline

  • 00:00:00 - 00:03:21

    Pain serves as a crucial defense mechanism by alerting the body to potential injuries or diseases. Noxious signals are relayed from the spinal cord to the brain, which interprets them as pain and sends instructions for protective actions. Pain receptors (nociceptors) are located in the skin and various organs, except for the brain, and are categorized into myelinated A fibers for sharp pain and unmyelinated C fibers for dull pain. Signals travel from first-order neurons to second-order neurons in the spinal cord, crossing to the opposite side before reaching the brain. Pain is transmitted through two primary pathways: the spinothalamic tract, involved in pain localization, and the spinoreticular tract, which addresses the emotional aspect of pain. Facial pain follows a distinct route via the trigeminal nerve. Somatic pain arises from skin, muscles, and joints, whereas visceral pain originates from internal organs and may be perceived in different locations (referred pain), such as feeling heart attack pain in the shoulder or arm due to overlapping pain pathways.

Mind Map

Video Q&A

  • What is the role of pain in the body?

    Pain serves as an important defense mechanism that warns the body about potential injuries or diseases.

  • What are nociceptors?

    Nociceptors are pain receptors located in the skin, superficial tissues, and most organs that mediate pain sensation.

  • What are the two types of pain fibers?

    The two types of pain fibers are myelinated A fibers, which conduct sharp pain quickly, and unmyelinated C fibers, which transmit dull, longer-lasting pain.

  • How do pain signals reach the brain?

    Pain signals travel from first-order neurons to second-order neurons in the spinal cord, then cross over to the other side and ascend to the brain.

  • What is referred pain?

    Referred pain occurs when pain from internal organs is felt in a different location due to the convergence of pain pathways.

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  • 00:00:02
    As undesirable as it might seem, pain is actually  a very important defense mechanism. It warns the
  • 00:00:10
    body about potential or actual injuries  or diseases, so that protective actions
  • 00:00:14
    can be taken. Basically, noxious signals  send impulses to the spinal cord, which
  • 00:00:20
    relays the information to the brain. The brain  interprets the information as pain, localizes it,
  • 00:00:26
    and sends back instructions for the body to react. Pain sensation is mediated by pain receptors,
  • 00:00:32
    or nociceptors, which are present in the skin,  superficial tissues and virtually all organs,
  • 00:00:38
    except for the brain. These receptors are  essentially the nerve endings of so-called
  • 00:00:42
    “first-order neurons” in the pain pathway. The  axons of these neurons can be myelinated, A type,
  • 00:00:49
    or, unmyelinated, C type. Myelinated A fibers  conduct at fast speeds and are responsible for
  • 00:00:56
    the initial sharp pain perceived at the  time of injury. Unmyelinated C fibers
  • 00:01:01
    conduct at slower speeds and are responsible  for a longer-lasting, dull, diffusing pain.
  • 00:01:08
    First-order neurons travel by way  of spinal nerves to the spinal cord,
  • 00:01:12
    where they synapse with second-order neurons  in the dorsal horn. These second-order neurons
  • 00:01:18
    cross over to the other side of the cord,  before ascending to the brain. This is how
  • 00:01:23
    information of pain on the left side  of the body is transmitted to the
  • 00:01:26
    right side of the brain, and vice versa. There are two major pathways that carry
  • 00:01:31
    pain signals from the spinal cord to the brain: - The spinothalamic tract: second-order neurons
  • 00:01:38
    travel up within the spinothalamic tract to the  thalamus where they synapse with third-order
  • 00:01:43
    neurons; third-order neurons then project to their  designated locations in the somatosensory cortex.
  • 00:01:49
    This pathway is involved in localization of pain. - The spinoreticular tract: second-order neurons
  • 00:01:58
    ascend to the reticular formation of the  brainstem, before running up to the thalamus,
  • 00:02:02
    hypothalamus, and the cortex. This tract is  responsible for the emotional aspect of pain.
  • 00:02:09
    Pain signals from the face follow a different  route to the thalamus. First-order neurons
  • 00:02:16
    travel mainly via the trigeminal nerve to the  brainstem, where they synapse with second-order
  • 00:02:21
    neurons, which ascend to the thalamus. Pain from the skin, muscles and joints
  • 00:02:27
    is called somatic pain, while pain from internal  organs is known as visceral pain. Visceral pain
  • 00:02:35
    is often perceived at a different location in a  phenomenon known as referred pain. For example,
  • 00:02:41
    pain from a heart attack may be felt in the left  shoulder, arm or back, rather than in the chest,
  • 00:02:47
    where the heart is located. This happens because  of the convergence of pain pathways at the spinal
  • 00:02:53
    cord level. In this example, spinal segments  T1 to T5 receive pain signals from the heart
  • 00:02:59
    as well as the shoulders and arms, and the  brain cannot tell them apart. Because the
  • 00:03:05
    superficial tissues have more pain receptors  and are more often injured, it’s common for the
  • 00:03:10
    brain to make an assumption that the pain comes  from the shoulder or arm instead of the heart.
Tags
  • Pain
  • Defense Mechanism
  • Nociceptors
  • Neurons
  • Somatic Pain
  • Visceral Pain
  • Referred Pain
  • Spinothalamic Tract
  • Pain Pathways
  • Pain Perception