Skeletal muscle
Say it: SKEL-uh-tul MUS-ul
Skeletal muscle is the striated, voluntary muscle tissue attached to bones by tendons that moves the body, holds posture and produces heat.
Also: voluntary muscle, skeletal muscles
Definition
What is skeletal muscle?
Skeletal muscle is one of the three types of muscle tissue, alongside cardiac and smooth muscle. Most skeletal muscles attach to bones through tendons and move the skeleton when they contract. It is called voluntary muscle because it contracts only when a motor neuron signals it, under conscious or reflex control. Under the microscope its long cells show regular stripes, or striations, produced by the orderly arrangement of actin and myosin filaments in repeating units called sarcomeres.
A skeletal muscle is built in layers. Each muscle cell, or muscle fiber, is a long cylinder with many nuclei, formed when embryonic cells called myoblasts fuse, and it can be many centimeters long. Each fiber is wrapped in connective tissue called endomysium; fibers are bundled into fascicles surrounded by perimysium; and the whole muscle is covered by epimysium, which continues into the tendon. A motor neuron triggers contraction at the neuromuscular junction by releasing acetylcholine, which sets off an action potential in the fiber and the release of stored calcium inside it.
Besides movement, skeletal muscles hold posture, stabilize joints, control openings such as those used in swallowing and urination, protect internal organs and generate heat, as in shivering.
Word parts
Where does the term “skeletal muscle” come from?
- skelet-
- dried up (a dried body)Greek skeletos
- muscle
- little mouseLatin musculus
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Terms that go with it
- SarcomereA sarcomere is the repeating contractile unit of striated muscle, the section of a myofibril between two Z-discs where actin and myosin interact.
- TendonA tendon is a tough cord of dense connective tissue linking a muscle to a bone, which passes on the muscle's pull to move it.
- BoneBone is the hard, mineralized connective tissue that makes up most of the adult skeleton, and the name for each skeletal organ built from it.
- AcetylcholineAcetylcholine is the neurotransmitter motor neurons use to make skeletal muscles contract, and a key messenger in the autonomic nervous system and brain.
- Action potentialAn action potential is a brief, all-or-none reversal of the voltage across a nerve or muscle cell membrane that travels along the cell as a signal.
- NeuronA neuron is a nerve cell, the basic signaling unit of the nervous system, which receives information and passes it on as electrical and chemical signals.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- OpenStax Anatomy and Physiology 2e, 10.2 Skeletal Muscle
- NCI SEER Training: Structure of Skeletal Muscle
- NCBI MeSH: Muscle, Skeletal
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