Chapter 11 - Regulation of movement

Abstract

The regulation of movement is primarily due to the skeletal muscles and central nervous system. The basic unit of skeletal muscle is the muscle fiber. The smooth muscles control movements in hollow organs, the stomach, intestines, and blood vessels. Cardiac muscle is only responsible for the heartbeat. The skeletal muscles are voluntary and are striated, with series of dark and light bands. They are activated by somatic motor neurons, with adenosine triphosphate (ATP) being the energy source. Muscle contractions may be isotonic (of changing length) or isometric (of constant length plus tension). Muscle fatigue occurs when contraction cannot occur, but stimuli continues to be received. The complicated mechanism of muscle fatigue involves alterations of excitation–contraction coupling and may implicate the chemical changes such as imbalances of ions, increased phosphate, decreased ATP, and decreased glycogen. Neurons and skeletal muscle cells are electrically excitable, so they generate action potentials that travel in waves. Many reflexes are regulated at the level of the spinal cord. Motor skills requiring voluntary control so that physical activities can be initiated. Motor learning is the process of acquiring a skill through practice and assimilation, in stages known as cognitive, associative, and autonomous. Movements are regulated as flexion, extension, abduction, adduction, circumduction, rotation, dorsiflexion, plantar flexion, pronation, supination, inversion, and eversion. With aging, regulation of movement may develop abnormalities such as apraxia (an inability to perform purposeful motor tasks).