Sollers III, in Encyclopedia of Stress (Second Edition), 2007 Background The preganglionic neurons synapse onto postganglionic neurons in the parasympathetic ganglion that are located next to, or in, the target organs. The parasympathetic nervous system originates in the sacral region of the spinal cord and the medulla in the brainstem. The axons of these neurons, via the ventral roots, synapse onto postganglionic neurons in the sympathetic chain that are located next to the spinal column. The sympathetic nervous system originates in the spinal cord, with the cell bodies of the preganglionic neurons located in the thoracic and lumbar regions. The sympathetic and parasympathetic divisions operate in parallel, with the former involved in the “fight or flight” response and the latter involved in “rest and digest” functions. The CNS has two neural outputs: the somatic motor system, which innervates and commands skeletal muscles through motor neurons in the ventral horn of the spinal cord, and the autonomic nervous system, which regulates the functions of the body's internal organs through the sympathetic, parasympathetic, and enteric nervous systems. Liu-Ambrose, in Handbook of Clinical Neurology, 2016 Autonomic
Īfter the central nervous system processes and integrates the information it receives from the peripheral structures, it sends out commands for action or inhibition of action to achieve a desired result.Ĭ.K. Īt every level, there is modulation and processing of the information with other afferent stimuli. Īfferent impulses may travel to one or several levels of the spinal cord before the information is sent out of the cord to the brain or to the periphery. Somatic afferent impulses may also be transmitted to somatic efferent cell bodies in the ventral horn, which send axons back to the muscles to regulate muscle length and tone, completing the somatosomatic reflex (see Fig. Vibratory sensation or proprioception is transmitted superiorly to the ipsilateral side of the brain, and other information, such as pain and temperature, is transmitted across the cord to the spinothalamic tract before being transmitted to the contralateral side of the brain ( Fig. The afferent information from the muscles and joints is transmitted to the dorsal root ganglion (DRG) and then to the dorsal horn of the spinal cord. Īfferent nerve impulses travel from the peripheral muscle or joint structures to the spinal cord, conveying information about pain, temperature, and position. LABEL THE MOTOR TRACTS OF THE SOMATIC NERVOUS SYSTEM. MANUAL
Manual treatments are designed to alleviate somatic dysfunction to help the motor system improve its efficiency.
The motor system continually adapts to injuries and somatic dysfunctions, but each adaptation is less efficient than its predecessor.
Įach component is functionally and structurally capable of adaptation and modulation to maintain as much efficiency as possible. Neural control of the somatic motor system involves complex feedback mechanisms between the brain, spinal cord, peripheral nerves, and musculoskeletal structures. Since the prefrontal cortex receives many afferents from limbic brain structures involved in emotional activity, one might argue that the somatic motor system is also a tool for the emotional brain to satisfy its needs. The prefrontal cortex might play an essential role in deciding whether or not a motor activity is necessary to react to a certain situation. The question is what drives the somatic motor system. In most mammals, both the lateral corticospinal and the rubrospinal pathways are important, but in humans the rubrospinal pathway seems to be irrelevant ( Fig. This descending system enables humans to make most refined and extremely complex movements, such as independent finger movements and speech, the most complicated motor performance. The motoneurons innervating the muscles of the distal limbs receive the strongest direct projections from the motor cortex. It controls the motoneurons via direct projections as well as indirectly via strong projections to the laterally located premotor interneurons. In humans, the lateral corticospinal pathway subserves the control of the independent movements of the extremities. This component consists of two pathways-the lateral corticospinal and the rubrospinal pathways. The lateral component of the somatic motor system controls the premotor interneurons and motoneurons of the distal muscles. GERRITS, in The Human Nervous System (Second Edition), 2004 Lateral Component of the Somatic Motor System
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