CVA Neurophysiology & Mechanisms of Acupuncture Action 1 — Questions and Answers
Question 1: The gate control theory of pain suggests that acupuncture analgesia occurs primarily through which mechanism?
- Activation of large-diameter Aβ fibers that inhibit pain transmission in the dorsal horn (Correct answer)
- Direct destruction of nociceptive nerve endings at the needle site
- Release of cortisol from the adrenal glands during needle stimulation
- Stimulation of the vagus nerve to suppress systemic immune responses
Correct answer: Activation of large-diameter Aβ fibers that inhibit pain transmission in the dorsal horn
Gate control theory proposes that large-diameter Aβ fiber activation in the dorsal horn closes the 'gate' to pain signals carried by smaller C and Aδ fibers, reducing pain transmission.
Question 2: Which endogenous opioid peptides are most directly responsible for acupuncture-induced analgesia?
- Cortisol and epinephrine released from the adrenal medulla
- Beta-endorphin, enkephalins, and dynorphins (Correct answer)
- Substance P and CGRP acting on peripheral receptors
- Histamine and serotonin released from mast cell degranulation only
Correct answer: Beta-endorphin, enkephalins, and dynorphins
Acupuncture stimulates the release of endogenous opioid peptides—beta-endorphin, enkephalins, and dynorphins—which bind mu, delta, and kappa opioid receptors to produce analgesia.
Question 3: The 'De Qi' sensation experienced during acupuncture needling is primarily associated with stimulation of which nerve fiber types?
- Only A-alpha motor fibers controlling skeletal muscle
- Exclusively unmyelinated C fibers in the skin
- A-delta (Group III) and C (Group IV) sensory fibers in muscle (Correct answer)
- Only large myelinated A-beta fibers transmitting touch
Correct answer: A-delta (Group III) and C (Group IV) sensory fibers in muscle
De Qi—the characteristic aching, distending sensation—is generated by activation of A-delta and C fibers in muscle tissue, which transmit signals initiating acupuncture's therapeutic cascade.
Question 4: Descending pain inhibitory pathways activated by acupuncture primarily originate from which brain regions?
- Cerebellum and basal ganglia controlling motor output
- Primary visual cortex and prefrontal cortex
- Hippocampus and amygdala regulating memory and emotion
- Periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) (Correct answer)
Correct answer: Periaqueductal gray (PAG) and rostral ventromedial medulla (RVM)
The periaqueductal gray (PAG) and rostral ventromedial medulla (RVM) are the primary sources of descending pain inhibitory pathways activated by acupuncture to suppress dorsal horn nociception.
Question 5: In veterinary acupuncture, 'somatovisceral reflexes' are best described as:
- Visceral organ dysfunction causing referred pain on the body surface
- Reflexes in which somatic stimulation via acupuncture points modulates internal organ function through spinal cord pathways (Correct answer)
- Contraction of skeletal muscles in direct response to visceral organ pain
- Autonomic nervous system control of somatic muscle tone during disease
Correct answer: Reflexes in which somatic stimulation via acupuncture points modulates internal organ function through spinal cord pathways
Somatovisceral reflexes occur when stimulation of somatic structures (skin, muscles) at acupuncture points sends signals through spinal cord pathways that modulate visceral organ function.
Question 6: Which neurotransmitter, released via descending raphe nucleus pathways during acupuncture, contributes to both spinal analgesia and anti-inflammatory effects?
- Serotonin (5-HT) acting on dorsal horn 5-HT receptors (Correct answer)
- Acetylcholine acting at neuromuscular junctions
- Glutamate activating NMDA receptors in the dorsal horn
- Dopamine modulating reward pathways in the striatum
Correct answer: Serotonin (5-HT) acting on dorsal horn 5-HT receptors
Serotonin released from descending raphe nucleus projections into the dorsal horn during acupuncture contributes to inhibition of nociceptive transmission and modulation of inflammatory mediators.
Question 7: Segmental acupuncture treatment is based on which neuroanatomical principle?
- Targeting points within the same spinal segment (dermatome/myotome/sclerotome) as the pathological structure (Correct answer)
- Dividing the body into equal anatomical halves and treating symmetrically
- Using only Governing Vessel (Du Mai) points along the dorsal midline
- Applying needles sequentially from cranial to caudal along the spine
Correct answer: Targeting points within the same spinal segment (dermatome/myotome/sclerotome) as the pathological structure
Segmental acupuncture places needles within the same spinal cord segment as the target organ or tissue, exploiting somatosensory and autonomic convergence at that spinal level.
CVA Neurophysiology & Mechanisms of Acupuncture Action 1
The gate control theory of pain suggests that acupuncture analgesia occurs primarily through which mechanism?