Muscle

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Muscle
Three distinct types of muscle (L to R): smooth (non-striated), cardiac, and skeletal muscle
Identifiers
MeSH	D009132
TA2	1975, 1994
FMA	5022 30316, 5022
Anatomical terminology [edit on Wikidata]

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. Among many other muscle proteins, present are two regulatory proteins, troponin and tropomyosin.^[1]

Muscle tissue varies with function and location in the body.

In vertebrates, the three types are:

1. skeletal,
2. cardiac (both striated), and
3. smooth muscle (non-striated).^[2]

Skeletal muscle tissue consists of elongated, multinucleate muscle cells called muscle fibers, and is responsible for movements of the body. Other tissues in skeletal muscle include tendons and perimysium.^[3] Smooth and cardiac muscle contract involuntarily, without conscious intervention. These muscle types may be activated both through the interaction of the central nervous system as well as by receiving innervation from peripheral plexus or endocrine (hormonal) activation. Striated or skeletal muscle only contracts voluntarily, upon the influence of the central nervous system. Reflexes are a form of non-conscious activation of skeletal muscles, but nonetheless arise through activation of the central nervous system, albeit not engaging cortical structures until after the contraction has occurred.^{[citation needed]}

The different muscle types vary in their response to neurotransmitters and hormones such as acetylcholine, noradrenaline, adrenaline, and nitric oxide depending on muscle type and the exact location of the muscle.^{[citation needed]}

Sub-categorization of muscle tissue is also possible, depending on among other things the content of myoglobin, mitochondria, and myosin ATPase etc.^{[citation needed]}