IN-DEPTH: COMPLEMENTARY MEDICINE Good cellular CIS, as can be surmised, will lead to


the production of healthy connections with the goal of contributing to create plasticity of those pathways. Plasticity can be described as healthy neurons making more connections between one another, strengthening a pathway or neuronal pool. Plasticity could become a double-edged sword if the neurons being stimulated are classified as small diameter fibers which carry nociceptive information. In the field of manipulative therapy, proper or


correct stimulation is the beginning to recovery! The practitioner needs to realize that overstimulation may stop recovery and make the patient prone to reinjury and/or worsening of clinical symptoms. The mechanism for how overstimulation causes damage or worsening of the clinical signs is by ex- ceeding the “patient’s local energy resources” due to exceeding its normal metabolic rate. Assessment of heart rate, respiratory rate, blood pressure, and pupillary light reflex provide the clinician with a window assessing the balance between the parasym- pathetic and sympathetic system.


5. Spinal Cord


Embryologically, the CNS (brain and spinal cord) and many of its basic connections are derived from the ectodermal layer of the embryo.19,20 It is amaz- ing how two cells (from different individuals) come together, start replicating to form a three-layer em- bryo (from one layer) at the same time that it elongates in a process described as “cephalization.”19,21,22 The spinal cord extends from the foramen magnum to next to the last vertebral body depending on the size and breed of the horse. Please note that each spinal nerve is composed of several rootlets that represent a somite (segment) and each segment has a dermatomal and myotomal representation. The spinal cord contains the white matter (which contain tracts) on the periph- ery and the gray matter (“butterfly” section and which contains cell bodies) on the center (as opposed to what is found in the cortex) with a central canal within the gray matter. The central canal is an anatomical ex- tension of the ventricles and contains cerebrospinal fluid. As a reminder, the gray matter mainly contains


cell bodies of neurons and it is divided into four sections (dorsal/lateral and ventral horn with an intermediate column). The dorsal horn contains sensory nuclei that receive afferent sensory informa- tion. From the dorsal horn, the afferent divergent information goes to local and suprasegmental levels. The intermediolateral column and the lateral horn comprise autonomic neurons innervating visceral and pelvic organs representing the autonomic ner- vous system.22,23 Finally, the ventral horn con- tains several kinds of motor neurons that innervate specific end organs. The cell bodies found within the gray matter can be divided into the following: root cells (those found within the ventral and lateral horns and they are further divided into somatic ef- ferent and visceral efferent), column or tract cells or


commissure association cells, and, lastly, the pro- priospinal cells (subclassified as different kinds of “interneuron” cells), which comprise (as described by some anatomists) about 90% of all of the spinal neurons.24–26 The white matter of the spinal cord contains my- elinated nerve fibers that either ascend or descend within the spinal cord. The outer section of the spinal cord is divided into the dorsal funiculus, lat- eral funiculus, and ventral funiculus. There is a specific anatomical region of the spinal cord named the “ventral or anterior commissure,” which con- tains nerve fibers that cross from one side of the body to the other.


6. Ascending Tracts22,27,28


Dorsal Columns–Medial Lemniscus Tract: These tracts are found within the dorsal funiculus of the white matter. They provide the body with two- point discrimination (through information provided by the Meissner, Pacinian, and Merkel Corpuscles of the region), vibration, and ultimately (once it is rec- ognized in the somatosensory cortex among others) proprioception. This tract is described as a three3- neuron connection path. Anterolateral/Ventrolateral or Spinothalamic


Tract: Please note that the description presented will be basic and simplistic. This tract is located in the ventrolateral funiculus of the white matter and carries information that deals with crude touch, temperature, and nociception (with the latter lead- ing to the recognition of pain). This tract is also a three-neuron connection tract.


7. Spinocerebellar Tracts


Cuneo-Cerebellar Tract: Afferent information (from GTOs, joint mechanoreceptors, and some MSC) is received from the spinal cord levels of C8 to C1. This is a two-neuron connection tract. Dorsal Spinocerebellar Tract (DSCT): As with the cuneocerebellar tract, these fibers carry unconscious, proprioceptive – or better described as reflexogenic information – from GTOs, joint mechanoreceptors and some MSC originating distal to the spinal cord level of T1 to L3/4 spinal cord level. As with the cuneocer- ebellar tract, this is a two-neuron connection tract. Ventral Spinocerebellar Tract (VSCT): The VSCT


carries information from the same receptors as the DSCT that originate in the lower extremity and trunk. This tract is also a two-neuron connection. Please note that this tract is a “special one” in which it is the only tract to the author’s knowledge that “double decussates” once at the spinal cord level and at the pontine region.


8. Basic Cortical Anatomy


Frontal lobe: Divided into primary motor, premo- tor, prefrontal, and supplementary motor area. Parietal lobe: Described as the primary somato- sensory area (for processing of tactile and mechan-


AAEP PROCEEDINGS  Vol. 64  2018 317


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