STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY STEVE GSCHMEISSNER / SCIENCE PHOTO LIBRARY
Striated muscle. Coloured scanning electron micrograph (SEM) of human striated muscle fibres. Striated muscle occurs in all skeletal muscles and its movement is under conscious (voluntary) control. Several rod-like muscle fibres can be seen running vertically, each being an elongated muscle cell formed from a group of contractile elements called myofibrils. Nervous impulses result in the release of calcium ions from the membranous sarcoplasmic reticulum (green). This causes filaments within the myofibrils to slide over one another and contract the muscles. The striations of skeletal muscle are not visible here. Magnification unknown.
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