Why pain exists, what detects it, how it climbs to the cortex, why it is sometimes felt far from the organ that hurts, and how the body turns it down again. Examiners ask most for the pain pathways traced on a labelled diagram, for referred pain and its theories, and for the endogenous analgesia system with a note on opiate receptors.
Topics, in the book’s order
- Pain: concepts, receptors and fibers · pp. 1014–1016 · asked once
- Pain pathways and perception · pp. 1016–1020 · asked 5 times
- Visceral and referred pain · pp. 1018–1020 · asked 9 times
- Endogenous pain control and gate control theory · pp. 1020–1022 · asked twice
- Specific pain syndromes · p. 1022 · asked once
- Itch and temperature sensation · p. 1023
When you’ve read them: Quiz 120 · Physiology of Pain, Itch and Temperature, 15 questions.
After this chapter you should be able to
- define pain and classify it
- name the nociceptors, say where they lie and how each behaves
- draw and label the pain pathways
- list what separates somatic pain from visceral pain
- define referred pain and account for it
- explain how a noxious stimulus is recognized as pain, and what alters that perception
- describe the body’s own analgesia systems
- explain the physiology of itch and of temperature sensation
Going further: the reasoning behind each somatic–visceral difference, and the case for each theory of referred pain.
Viva checklist
- The IASP definition of pain; what “nociceptive” means
- Types of pain: fast and slow, superficial and deep, somatic and visceral, peripheral and central, physiologic and pathologic
- The three groups of nociceptors, and the fiber each belongs to
- Vanilloid receptors, CMR1, and the TRP family of channels
- Laminae where Aδ and C fibers end; Lissauer’s tract
- The tract that carries pain, and the two pathways inside the anterolateral system
- Topographic arrangement of pain fibers in the spinothalamic tract
- Thalamic nuclei for fast pain and for slow pain, and what each pathway contributes
- The chemicals that excite nociceptors; the part played by substance P
- Differences between somatic and visceral pain
- Referred pain: definition, two classic examples, and the four theories
- The two descending analgesia pathways, their transmitters and their origins
- Classes of opiate receptor, the endorphins, and what naloxone does
- Gate control theory, and how acupuncture is thought to work
- Hyperalgesia, hypoalgesia, hyperpathia, allodynia, causalgia
- Receptors and pathway for itch; the temperature ranges of warm and cold receptors