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There is no such thing. Were something non-contractile, it would cease to be called a muscle. You probably meant "What is a contractile muscle structure?" or something similar. There are many such answered questions on here.
series-elastic elements
The non-contractile element are skeletal muscles that don't contract such as Epimysium,Perimysium and, Endomysium. Contractile muscle contract as a whole muscle instead of single bundles of muscle fibers
the so called longitudinal bundles in the cytoplasm of a skeletal muscle are actually the muscle contractile proteins, namely actin and myosin.
This will depend upon the number of muscle fibers the nerve innervates. However, all fibers innervated by the nerve should contract in response to the neuronal impulse.
Sarcomere
The sarcomere is the contractile unit of a muscle fiber.
No, it has myogenic contractile ability. Source: Physiology book
Sarcomere
sacromere
muscles
Actin and Myosin