Neural Control of Muscle Length and Tension

2011 ◽  
Author(s):  
James C. Houk ◽  
W. Zev Rymer
Keyword(s):  
Neural Control ◽  
Muscle Length

Differential costal and crural diaphragm compensation for posture changes

1985 ◽  
Vol 58 (6) ◽  
pp. 1895-1900 ◽  
Author(s):  
E. van Lunteren ◽  
M. A. Haxhiu ◽  
N. S. Cherniack ◽  
M. D. Goldman
Keyword(s):  
Neural Control ◽  
Muscle Length ◽  
Control Mechanisms ◽  
Fine Wire ◽  
Supine Posture ◽  
Crural Diaphragm ◽  
Resting Muscle

The electromyographic (EMG) activities of the costal and crural diaphragm were recorded from bipolar fine-wire electrodes placed in the costal fibers adjacent to the central tendon and in the anterior portions of the crural fibers in 12 anesthetized cats. The EMG activities of costal and crural recordings were compared during posture changes from supine to head up and during progressive hyperoxic hypercapnia in both positions. The activity of both portions of the diaphragm was greater in the head up compared with supine posture at all levels of CO2; and increases in crural activity were greater than those in costal activity both as a result of changes in posture and with increasing CO2 stimuli. These results are consistent with the concept that diaphragm activation is modulated in response to changes in resting muscle length, and further, that neural control mechanisms allow separate regulation of costal and crural diaphragm activation.

scholarly journals Age-related changes in leg proprioception: implications for postural control

2019 ◽  
Vol 122 (2) ◽  
pp. 525-538 ◽  
Author(s):  
Mélanie Henry ◽  
Stéphane Baudry
Keyword(s):  
Postural Control ◽  
Neural Control ◽  
Body Position ◽  
Muscle Length ◽  
Functional Independence ◽  
Body Sway ◽  
Neural Pathways ◽  
Age Related ◽  
Proprioceptive Signal ◽  
Upright Standing

In addition to being a prerequisite for many activities of daily living, the ability to maintain steady upright standing is a relevant model to study sensorimotor integrative function. Upright standing requires managing multimodal sensory inputs to produce finely tuned motor output that can be adjusted to accommodate changes in standing conditions and environment. The sensory information used for postural control mainly arises from the vestibular system of the inner ear, vision, and proprioception. Proprioception (sense of body position and movement) encompasses signals from mechanoreceptors (proprioceptors) located in muscles, tendons, and joint capsules. There is general agreement that proprioception signals from leg muscles provide the primary source of information for postural control. This is because of their exquisite sensitivity to detect body sway during unperturbed upright standing that mainly results from variations in leg muscle length induced by rotations around the ankle joint. However, aging is associated with alterations of muscle spindles and their neural pathways, which induce a decrease in the sensitivity, acuity, and integration of the proprioceptive signal. These alterations promote changes in postural control that reduce its efficiency and thereby may have deleterious consequences for the functional independence of an individual. This narrative review provides an overview of how aging alters the proprioceptive signal from the legs and presents compelling evidence that these changes modify the neural control of upright standing.

scholarly journals Robust passive dynamics of the musculoskeletal system compensate for unexpected surface changes during human hopping

2009 ◽  
Vol 107 (3) ◽  
pp. 801-808 ◽  
Author(s):  
Marjolein M. van der Krogt ◽  
Wendy W. de Graaf ◽  
Claire T. Farley ◽  
Chet T. Moritz ◽  
L. J. Richard Casius ◽  
...  
Keyword(s):  
Neural Control ◽  
Joint Stiffness ◽  
Muscle Length ◽  
Musculoskeletal Model ◽  
Muscle Stiffness ◽  
Passive Dynamics ◽  
Hard Surface ◽  
Surface Stiffness ◽  
Leg Stiffness ◽  
Soft Surface

When human hoppers are surprised by a change in surface stiffness, they adapt almost instantly by changing leg stiffness, implying that neural feedback is not necessary. The goal of this simulation study was first to investigate whether leg stiffness can change without neural control adjustment when landing on an unexpected hard or unexpected compliant (soft) surface, and second to determine what underlying mechanisms are responsible for this change in leg stiffness. The muscle stimulation pattern of a forward dynamic musculoskeletal model was optimized to make the model match experimental hopping kinematics on hard and soft surfaces. Next, only surface stiffness was changed to determine how the mechanical interaction of the musculoskeletal model with the unexpected surface affected leg stiffness. It was found that leg stiffness adapted passively to both unexpected surfaces. On the unexpected hard surface, leg stiffness was lower than on the soft surface, resulting in close-to-normal center of mass displacement. This reduction in leg stiffness was a result of reduced joint stiffness caused by lower effective muscle stiffness. Faster flexion of the joints due to the interaction with the hard surface led to larger changes in muscle length, while the prescribed increase in active state and resulting muscle force remained nearly constant in time. Opposite effects were found on the unexpected soft surface, demonstrating the bidirectional stabilizing properties of passive dynamics. These passive adaptations to unexpected surfaces may be critical when negotiating disturbances during locomotion across variable terrain.

Morphological Basis of the Disparity Between Muscle Length and Sarcomere Length in the Myocardium

1973 ◽  
Vol 31 ◽  
pp. 422-423
Author(s):  
G.E. Adomian ◽  
L. Chuck ◽  
W.W. Pannley
Keyword(s):  
Cardiac Muscle ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Contractile Force ◽  
Direct Function ◽  
Morphological Basis ◽  
Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

Neural Control of Reproduction

1998 ◽  
Vol 48 (3) ◽  
pp. 375-376
Author(s):  
Robert A. Steiner
Keyword(s):  
Neural Control
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