© 2013 the American Physiological Society.Ībstract = "Whereas muscle spindles play a prominent role in current theories of human motor control, Golgi tendon organs (GTO) and their associated tendons are often neglected.
The theoretical analyses in this study might furthermore provide insight about the strong physiological couplings found between muscle spindle and GTO afferents in the human nervous system. Simulations showed that the proposed feedback could be easily incorporated in the optimal control framework without complicating the computation of the optimal control solution, yet greatly enhancing the system's response to perturbations. Finally, we incorporated the proposed scheme in an optimally controlled 2-DOF model of the arm for fast point-to-point shoulder and elbow movements. Responses to transient and static perturbations were simulated using a 1-degree-of-freedom (DOF) model of the arm and showed that the combined feedback enabled the system to respond faster, reach steady state faster, and achieve smaller static position errors. The feasibility of the proposed scheme was tested using detailed musculoskeletal models of the human arm. We propose that a combination of spindle and GTO afferents can provide an estimate of muscle-tendon complex length, which can be effectively used for low-level feedback during both postural and movement tasks. Using detailed musculoskeletal models, we provide evidence that simple feedback using muscle spindles alone results in very poor control of joint position and movement since muscle spindles cannot sense changes in tendon length that occur with changes in muscle force. This is surprising since there is ample evidence that both tendons and GTOs contribute importantly to neuromusculoskeletal dynamics. Planning of motor activity takes place in the forebrain and motor function is modulated by input from the cerebellum and basal nuclei.Whereas muscle spindles play a prominent role in current theories of human motor control, Golgi tendon organs (GTO) and their associated tendons are often neglected. The ‘Neuro RAT’ helps differentiate between UMN and LMN signs – Reflexes, Atrophy and Tone. Muscle atrophy can be severe and is neurogenic in origin. Loss of the LMNs results in paresis/paralysis, with decreased to absent muscle tone and reflexes.
Muscle atrophy is mild and due to disuse. Loss of UMN input typically results in paresis or paralysis with normal to increased muscle tone and spinal reflexes caudal to the lesion. Movement is ultimately expressed through the LMNs stimulating muscles. Specific UMN tracts are excitatory or inhibitory to LMNs. In quadrupeds, this system is of primary importance. Extrapyramidal UMN tracts originate primarily in the brainstem and their fibres do not travel in the pyramids. The extrapyramidal system is responsible for maintaining posture and rhythmical/semiautomatic activities including locomotion. It is more important in primates and humans than quadrupeds. The UMN system originating from the motor cortex is responsible for voluntary and learned movement of the face, body and limbs using the corticonuclear and corticospinal/pyramidal tracts, respectively. Loss of inhibitory UMN function results in increased muscle tone and spinal reflexes, whereas loss of facilitatory UMNs results in paresis or paralysis. UMNs initiate, regulate, modify and terminate the activity of the LMN. Muscle tone and bulk depends on LMN function. The reflex arc involves sensory input, connection in the CNS to the UMN, the LMN, neuromuscular junction and muscle.
A reflex is a stereotypical somatic or autonomic activity triggered by a specific stimulus.
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