The epimysium covers the whole surface of the muscle. A muscle is made up of many muscle fasciculi, which are surrounded by a thick collagenous layer of connective tissue called the epimysium. A group of muscle fibers surrounded by the perimysium is called a muscle fasciculus. The group of muscle fibers and the endomysium are surrounded by more connective tissue called the perimysium. A group of muscle fibers are encased within more connective tissue called the endomysium. This is called muscle fiber recruitment.Įach muscle fiber is surrounded by connective tissue called an external lamina.

Only a small number of muscle fibers will contract to bend one of our limbs, but if we wish to lift a heavy weight then many more muscles fibers will be recruited to perform the action. The nerve and the fibers it controls are called a motor unit. Each nerve will control a certain number of muscle fibers. This signals the muscle fibers to contract. When we choose to contract a muscle fiber-for instance we contract our bicep to bend our arm upwards-a signal is sent from our brain via the spinal cord to the muscle. Each muscle fiber is an individual muscle cell and may be anywhere from 1 mm to 4 cm in length. Skeletal muscles are made up of a number of muscle fibers. They are under conscious control, which means that we can consciously choose to contract a muscle and can regulate how strong the contraction actually is. Skeletal muscles are attached to the skeleton and are responsible for the movement of our limbs, torso, and head.

All or none principle definition