According to PearsonHigherEd.com, the sarcomere is the basic unit of contraction within a bundle of muscle fibers. Individual sarcomeres contain clearly defined bands of filaments which have a special terminology.Continue Reading
Each sarcomere is surrounded by Z lines which denote the boundary from one sarcomere to the next. I bands are that portion of the sarcomere which contain thin filaments. H bands contain thick filaments, and A bands contain a mix of thick and thin. BiologyGuide.net states that these differences in thickness produce the characteristic striations of skeletal muscle.
BiologyGuide.net also states that the differences in thickness represent differences in what the filaments are made of. I bands contain filaments made up of actin alone, while H bands contain myosin filaments alone; A bands contain lengths of myosin.
The University of Washington describes how the filaments are typically arranged within a sarcomere; thin filaments extend from the Z lines to the center of the sarcomere, with thick filaments in the middle. The thick filaments never get as far as the Z lines, but they overlap the thin filaments that do. The two kinds of filament slide in respect to one another, causing the Z lines to be pulled toward one another, creating a muscle contraction.Learn more about Muscles
The biceps are classified as skeletal muscles because they attach directly to the skeleton. According to Healthy Living, they are attached to the skeleton by tendons and are controlled voluntarily. As explained by education.com, skeletal muscles generally work in pairs; one muscle works in combination with an antagonistic muscle to move a joint such as the elbow or knee.Full Answer >
Both skeletal muscles and cardiac muscles contain striations among muscle cells and produce strong contractions, according to class notes from Yale University. Striations occur in crossing, alternating light and dark bands produced by proteins that make muscles contract, according to Dictionary.com.Full Answer >
The major types of muscle systems are the skeletal muscles, cardiac muscles and smooth muscles, explains Healthline. The skeletal muscles are voluntary muscles, whereas the smooth and cardiac muscles are involuntary ones.Full Answer >
Tonic smooth muscles show continuous contraction as fluids move around them, while phasic smooth muscles show rhythmic motions that cease after a time, according to class notes from Florida State University College of Medicine. Phasic smooth muscles include those within the wall of the stomach, and tonic smooth muscles are found in arteries.Full Answer >