This study is a continuation of the previous works on a theoretical description of the mechanism of motor control by the CNS under conditions of the performance of simple motor tasks by humans. We describe the process of development of maximal different-direction static efforts within the horizontal plane by the human arm, where the hand, shoulder joint, elbow joint, and the effort vector are within the same horizontal plane. The upper limb has been modelled by a musculoskeletal system comprising of the forearm and shoulder links, elbow and shoulder joints, and of eight muscles of the arm and brachial grid generating the corresponding forces. The problem has been reduced to that of linear programming and is resolved using the simplex method. The results of modelling demonstrated the existence of a complex system of optimization synergies, which changed significantly when the direction of the maximal effort vector was changed. This system of synergies is more complex in the case of generating the maximum effort with two arms connected at the palms. Despite the fact that the modelling results obtained looked rather unexpected and extraordinary from the aspect of a real neurophysiological research, they, nevertheless, can initiate some new ideas for experimental work.

Neurodegenerative diseases are characterized by a progressive loss of neuronal structures and functions. Although all biochemical and/or physiological processes are not completely understood, it is known that the main neurodegenerative diseases, like Alzheimer’s, Parkinson’s, Huntington’s, and prion diseases, and also amyotrophic lateral sclerosis (ALS) present certain obvious similarities. Biometal microelements, such as copper, iron, manganese, and zinc, are crucial for many physiological functions, especially in the CNS. Shifts in the amounts of these metals are essential for the development and maintenance of numerous enzymatic activities, mitochondrial functions, neurotransmission, and also for memorization and learning. However, with deregulations in their homeostasis, particularly in those connected with redox activity, there are consequent changes in the ion and microelement balance. This redox activity may contribute to the production of free radicals that can react with various organic substrates, thus generating increased levels of oxidative stress. There is growing evidence that metal microelements play significant roles in the pathogenesis of neurodegenerative diseases. The interaction between metals and CNS proteins is crucial in the development or absence of neurodegeneration. In this way, homeostasis of metal microelements represents a mechanism of extreme importance. Our paper aims at an updated and critical review of the role of the respective metals in neurodegenerative diseases and the main related pathogenic mechanisms.