Actions of Dopamine on the Skin and the Skeleton
Nira Ben-Jonathan in Dopamine, 2020
The musculoskeletal system provides form, support, stability, and movement to the body. It is made up of the bones of the skeleton, muscles, and joints. Bones provide shape, hold the body upright, and protect organs from injury. They also store minerals and contain the bone marrow where new blood cells are made. The three types of muscle—skeletal, cardiac and smooth—differ in cellular structure, location, and mode of action. Joints are the physical points of connection between two bones. Joints contain a variety of fibrous connective tissue, ligaments that connect bones to each other, tendons that connect muscle to bone, and cartilage that covers the ends of bone and provides cushioning. After briefly reviewing the basic properties of the musculoskeletal system and its regulation by the nervous system, the last two sections of the chapter focus on the involvement of dopamine in pathophysiology of this system.
The skeleton and muscles
Frank J. Dye in Human Life Before Birth, 2019
Skeletal muscle function is required for movement, breathing, maintenance and alteration of posture, and generation of heat (e.g., shivering). Multinucleated fibers of skeletal muscle do not proliferate. Maintenance of muscle tissue depends on satellite cells, found in close proximity to the muscle fibers. These satellite cells are a heterogeneous population with a small subset of muscle stem cells, termed satellite stem cells. These satellite stem cells are prepared for mobilization by stimuli, including physical trauma and growth signals. Once mobilized, satellite stem cells undergo symmetric divisions to expand their number or asymmetric divisions to give rise to committed satellite cells and thus progenitors. Myogenic progenitors proliferate and eventually differentiate through fusion with each other or to damaged fibers to reconstitute fiber integrity and function.
The movement systems: skeletal and muscular
Nick Draper, Helen Marshall in Exercise Physiology, 2014
To understand how muscular contraction is brought about, it is first important to understand how a muscle is stimulated to contract. Remember that nervous and muscle tissues are unique in that they are excitable – they can conduct an electrical current – hence stimulation of a muscle fibre at one point will rapidly lead to excitation of the whole fibre. The stimulus for muscular contraction comes from the nervous system, specifically motor neurons, and takes advantage of the excitable nature of these two tissues. When a muscular contraction is required for any movement, a nerve signal is sent to the necessary muscles to initiate the response. Once generated, a nerve impulse (or action potential) travels the length of a nerve very rapidly to reach the junction with the muscle fibres it innervates. At this junction, motor neurons divide into finger-like projections that enable one neuron to make contact with a number of muscle fibres.
A computational model of upper airway respiratory function with muscular coupling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Olusegun J. Ilegbusi, Don Nadun S. Kuruppumullage, Matthew Schiefer, Kingman P. Strohl
For the genioglossus (the major upper airway dilator muscle), we assumed that muscle contraction occurred for 3s along an anterior-posterior direction. The strength of the contraction was induced through a time-force function in the FE model. In reality, the contraction of muscle tissues is activated through impulses delivered through the motor nerve network, for instance, the hypoglossal nerve for genioglossus in the tongue (Eisele et al. 1997; Yoo and Durand 2005). Figure 3 shows the activation profile used in this study. The activation duration was chosen to mirror a typical neurostimulation procedure. The magnitude of the force at this stage was chosen through preliminary simulations with varying forces until a profile produced airway openings at the epiglottis level typically observed in trial applications of neurostimulation. The activation profile was used as a distributed load within the region of genioglossus muscle. We assumed the airway structure was initially at rest. Therefore, there was no activation for the first 3s of the simulation in order to allow the airway structure to reach stable condition under gravity in the lateral-posterior direction.
Modeling human gait cycle using FE method and results of backward kinematics
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
A. Wit, S. Wronski, J. Tarasiuk, Z. S. Hadiji, P. Lipinski, C. Dreistadt
Muscles main functionality is dynamic contraction and relaxation to provide leg movements. In our case, all elements have the ability to change their length under the influence of a given parameters. The thermal expansion capacity of the elements used was exploited to reproduce both forces and muscular elongations (Creuillot et al. 2015). In the case of leg, the large displacements and rotations have to be considered. For this reason, the large strain theory or geometric nonlinearities must be considered. The following expression was adapted to calculate the muscular contractions: S(t) is its current cross-section area. Physiological CrossSection area of all muscles was used. The Young’s modulus and coefficient of muscular contraction are adjustable parameters. The value of l0, l(t), and F(t) correspond to the initial and current muscle lengths and muscular force. They were obtained from the calculations made with OPENSIM. The model was implemented under ABAQUS environment.
An approach to generate noncontact ACL-injury prone situations on a computer using kinematic data of non-injury situations and Monte Carlo simulation
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
R. Eberle, D. Heinrich, A. J. van den Bogert, M. Oberguggenberger, W. Nachbauer
Here q, FM the muscle forces, which depend on the muscle fiber lengths LCE, the contraction velocities a. The movement of the skier was controlled by 16 muscles—eight muscles for the right and left lower extremity, respectively: iliopsoas, glutei, hamstrings, rectus, vasti, gastrocnemius, soleus, tibialis anterior (Figure 1). Each muscle was modeled with a three element Hill-type model (Zajac 1989) with contraction dynamics (McLean et al. 2003) 1991) u denotes the muscle excitations. The muscle properties were taken from Gerritsen et al. (1996). Combining equations (1), (2) and (3) yielded the dynamics of the musculoskeletal model as a system of implicit differential equations (van den Bogert et al. 2011) q of the skier-ski model, 25 generalized velocities LCE and 16 muscle activations a) as well as 16 control variables u.
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