Figure 6-9 Anatomic depictions of ascending pathways that represent the needling reflex at different levels (see text). A, Nerve entry. Large-diameter afferent nerves enter the spinal cord and terminate in the first somatosensory area of the cerebral cortex through thalamocortical axons. B, Organization of the spinothalamic tract and remainder of the anterolateral system. The spinal cord itself terminates with primary axons. Second-order axons cross the middle line and ascend through the spinal cord and brainstem to terminate in the thalamus. Collateral extensions of these axons terminate in the reticular formation of the pons and medulla. This organization represents part of the needling pathways.
process of needling therapy. Needling-induced reflex responses occur at different levels of the nervous system:
• The segmental axon reflex, which consists of spinal interneuron and motor neuron reflexes, including interneuron inhibition and excitation responses and autonomic nerve reflexes
• The brainstem and pontine reticular formation reflexes, which mediate visceral physiology
• The midbrain periaqueductal gray reflex, which mediates the descending control of pain
• The thalamus and hypothalamus reflexes, which mediate homeostasis regulation of the system
• The limbic system reflex, which mediates regulation of the thalamus and hypothalamus
• Cortex involvement, including psychologic processes and cognitive modulation of peripheral conditions
The classic concept of the pathways of the needling reflex is illustrated as follows: Painful or injured tissues send messages to the spinal cord. The local spinal cord processes the incoming signal bidirectionally. The local spinal circuits regulate the signals through the biochemical effect of interneurons and motor neurons. Simultaneously, the incoming peripheral signals are relayed up through pathways to supraspinal levels: the brain-stem, thalamus, hypothalamus, limbic system, and cortex.
When needling is used to treat pain, both local (segmental circuit) and distal (nonsegmental circuit) sensitive points are selected. Wherever the needle is inserted, it stimulates afferent sensory receptors of the small-diameter nerves in skin and muscle as discussed previously: cutaneous AS and C fibers, muscular type III (AS) and IV (C) muscle fibers, sometimes type II muscle fibers, and AP muscle fibers.
During the needling of a local point in the painful area, the impulses travel from the acu-reflex point to the spinal cord to activate spinal neurons and to secrete enkephalin and dynorphin to inhibit the pain messages. Next, the needle impulses are relayed through spinal cells to the midbrain and the pituitary gland. The midbrain uses enkephalin to activate the raphe-descending pain-inhibition system.
The pain-inhibition system secretes monoam-ines, serotonin, and norepinephrine to inhibit pain transmission in two ways:
2. Activation of spinal cord neurons to synergisti-cally inhibit incoming pain message from painful tissues: The pituitary gland and hypothalamus, activated by the needling signals from the spinal cord, release P-endorphin into the blood and cerebrospinal fluid, which promotes physiologic analgesia and homeostasis of numerous systems, including the immune system, cardiovascular system, respiratory system, and system of tissue healing.
Finally, the needling signals generate neuronal activity at the highest brain level, the neocortical area.16 This cortical processing is responsible for modulating the perception of pain.
When distal points (nonsegmental circuits) are selected, the needle impulses bypass the spinal cord neurons and travel directly to the supraspinal level: the midbrain and pituitary gland, hypothalamus, and thalamus. Local points (segmental circuits) activate the spinal cord in addition to the midbrain, pituitary gland, and hypothalamus. To achieve maximal results, clinicians should activate both segmental and nonsegmental circuits.
In summary, local (symptomatic) points directly inhibit pain messages, whereas distal (homeostatic) points promote systemic homeostasis. Together they synergistically enhance pain relief and promote healing.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.