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Muscles provide strength, balance, posture, movement, and heat for the body to keep warm. [3] There are more than 600 muscles in an adult male human body. [4] A kind of elastic tissue makes up each muscle, which consists of thousands, or tens of thousands, of small muscle fibers.
Only skeletal and smooth muscles are part of the musculoskeletal system and only the muscles can move the body. Cardiac muscles are found in the heart and are used only to circulate blood; like the smooth muscles, these muscles are not under conscious control. Skeletal muscles are attached to bones and arranged in opposing groups around joints. [8]
All movements, e.g. touching your nose, require motor neurons to fire action potentials that results in contraction of muscles. In humans, ~150,000 motor neurons control the contraction of ~600 muscles. To produce movements, a subset of 600 muscles must contract in a temporally precise pattern to produce the right force at the right time. [6]
Depiction of smooth muscle contraction. Muscle contraction is the activation of tension-generating sites within muscle cells. [1] [2] In physiology, muscle contraction does not necessarily mean muscle shortening because muscle tension can be produced without changes in muscle length, such as when holding something heavy in the same position. [1]
These chemical reactions produce adenosine triphosphate (ATP) molecules that are used to power the movement of the myosin heads. [6] Skeletal muscle comprises about 35% of the body of humans by weight. [7] The functions of skeletal muscle include producing movement, maintaining body posture, controlling body temperature, and stabilizing joints. [8]
Muscle is a soft tissue, one of the four basic types of animal tissue. Muscle tissue gives skeletal muscles the ability to contract. Muscle is formed during embryonic development, in a process known as myogenesis. Muscle tissue contains special contractile proteins called actin and myosin which interact to cause movement.
The central nervous system has two distinct ways of controlling the force produced by a muscle through motor unit recruitment: spatial recruitment and temporal recruitment. Spatial recruitment is the activation of more motor units to produce a greater force.
Muscle redundancy is a degrees of freedom problem on the muscular level. [18] The central nervous system is presented with the opportunity to coordinate muscle movements, and it must choose one out of many. The muscle redundancy problem is a result of more muscle vectors than dimensions in the task space.