White matter- it consists of myelinated nerve fibers and glial cells. Different messages transmitted within the nervous system pass from the white to the gray matter. The myelination of the nerves enhances the speed of transmission of nerve signals (Mtui et al., 2020). Moreover, it provides electrical insulation allowing increased transmission of information from one place to another.
Gray matter- it is functionally classified in 3 varied ways; into four main columns, into six different nuclei, and into ten rexed laminae. The four columns include dorsal horn, ventral horn, intermediate horn, and lateral horn (Mtui et al.,2020). Dorsal horn also known as the (posterior horn) contains neurons that transmit information to the brain. The neurons are specialized in transmitting the body’s somatosensory information through the ascending pathways to the brain. Additionally, the ventral horn contains motor neurons in abundance which innervate the skeletal muscle while the lateral and intermediate columns contain a neuronal innervation of the pelvic and visceral organs (Mtui et al., 2020). The prominent spinal cord nuclei comprise of; substantia gelatinosa, nucleus proprious, dorsal nucleus of Clarke, marginal zone, lateral and medial motor neurons, and interomediolateral nucleus. Most of the nuclei are functionally mediated to relay sensory information (temperature, pain, touch, proprioception) from the viscera to the brain. The ten rexed laminae partially corresponds to the functions of the spinal cord nuclei.
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Roots- 31 nerve roots pair to form spinal nerves. The spinal nerves contain both the motor (anterior root) and sensory (posterior root) nerve fibers that innervates all body segments namely, sacral, lumbar, sacral and thoracic (Mtui et al., 2020). Spinal nerve divides into (posterior rami and anterior rami) at the point where it exits the vertebral canal through the intervertebral foramina.
Reflex- it is an impulsive or unplanned movement due to certain stimuli.
Spinal reflex- an involuntary movement due to a stimulus which evokes the spinal motor neurons to cause contraction or twitch of the involved muscles (Bhuiyan et al., 2017). The stimuli can act on the skin nociceptors or the muscle stretch receptors.
A reflex arc involves 5 components- motor neuron, sensory neuron, sensory receptor, integration target, and effector target.
Spinal cord injury (SCI) refers to mutilation of any segment of the spinal cord including the cauda equina (nerves at the end of the spinal canal). It results to loss of function, sensation, and strength in areas below the area of damage. With the broadening of human activities there is increased prevalence of SCI, the values also value among the developing and non- developed countries. In the United States there are an annual incidence of SCI of about 17,700 cases, and about 54 cases in every one million people (White & Black, 2017). These estimates are attributed by lower rates of school enrollment, violence, falls, and road traffic crashes.
Neurological level- the extreme caudal segment on both sides of the body of the spinal cord containing normal functioning of the sensory and motor parts.
Tetraplegia(quadriplegia) partial or total paralysis of all the four limbs due to illness or injury. Paraplegia is similar to tetraplegia with an exclusion of the arms.
Dermatome- segment of the body (skin) innervated by a single spinal nerve.
Myotome – muscles supplied by a single spinal nerve root.
The sensory and motor sensations are coupled in examining the neurological level (Ahuja et al., 2017). The agreement of an individual motor level checked from the myotome and sensory level from the dermatomes are vital in examining SCI.
Stretch reflex- refers to muscle contraction as a result of passive stretching. As long as the stretch is within the physiological limits the muscle’s contractility. It is a constant process of stretching and adjusting and maintains proper posturing.
Neurological level (L2- L4)
Injuries below the neurological level affect the hips and the leg and cause numbness to the feet. The management includes providing ambulatory long leg walking devices for short distances.
References
Ahuja, C. S., Schroeder, G. D., Vaccaro, A. R., & Fehlings, M. G. (2017). Spinal cord injury—what are the controversies?. Journal of orthopaedic trauma , 31 , S7-S13.
Bhuiyan, P. S., Rajgopal, L., & Shyamkishore, K. (2017). Inderbir Singh's Textbook of Human Neuroanatomy:(Fundamental & Clinical) . JP Medical Ltd.
Mtui, E., Gruener, G., & Dockery, P. (2020). Fitzgerald's Clinical Neuroanatomy and Neuroscience E-Book . Elsevier.
White, N. H., & Black, N. H. (2017). Spinal Cord Injury Facts and Figures at a Glance. National Spinal Cord Injury Statistical Center, Facts and Figures at a Glance Birmingham, AL: University of Alabama at Birmingham .
