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The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...
Drive reduction theory, developed by Clark Hull in 1943, is a major theory of motivation in the behaviorist learning theory tradition. [1] "Drive" is defined as motivation that arises due to a psychological or physiological need. [2] It works as an internal stimulus that motivates an individual to sate the drive. [3]
In spinal shock, which is commonly seen in the transection of the spinal cord, hyporeflexia can transiently occur below the level of the lesion and can later become hyperreflexic. Cases of severe muscle atrophy or destruction may render the muscle too weak to show any reflex and should not be confused with a neuronal cause. [citation needed]
Longer-term hypertrophy occurs due to more permanent changes in muscle structure. Hirono et al. explained the causes of Muscle swelling: [10] "Muscle swelling occurs as a result of the following: (a) resistance exercise can increase phosphocreatine and hydrogen ion accumulations due to blood lactate and growth hormone production, and
Central fatigue is a reduction in the neural drive or nerve-based motor command to working muscles that results in a decline in the force output. [3] [4] [5] It has been suggested that the reduced neural drive during exercise may be a protective mechanism to prevent organ failure if the work was continued at the same intensity.
Following denervation, muscular atrophy and degeneration occurs within affected skeletal muscle tissue. Within the skeletal tissue is observable progressive loss of weight of denervated muscles as well as reduction in muscle fiber size and quantity.
Aging is associated with decreases in muscle mass and strength. These decreases may be partially due to losses of alpha motor neurons. By the age of 70, these losses occur in both proximal and distal muscles. In biceps brachii and brachialis, old adults show decreased strength (by 1/3) correlated with a reduction in the number of motor units ...
Resistance training has been shown to dramatically increase performance of motor units of the larger muscle groups. [2] Motor unit plasticity of the larger muscle groups is extremely important for athletes, especially those participating in high impact and fast pace sports such as track and field, martial arts, and American football.