Extrafusal muscle fiber Extrafusal muscle fiber Extrafusal muscle fibers are the skeletal standard muscle fibers that are innervated by alpha motor neurons and generate tension by contracting, thereby allowing for skeletal movement. They make up the large mass of skeletal muscle tissue and are attached to bone by fibrous tissue extensions (tendons). Each alpha motor neuron and the extrafusal muscle fibers innervated by it make up a motor unit. The connection between the alpha motor neuron and the extrafusal muscle fiber is a neuromuscular junction, where the neuron's signal, the action potential, is transduced to the muscle fiber by the neurotransmitter acetylcholine. Extrafusal
Obliquus capitis superior muscle Obliquus capitis superior muscle The obliquus capitis superior muscle () is a small muscle in the upper back part of the neck and is one of the suboccipital muscles and part of the suboccipital triangle. It arises from the lateral mass of the atlas bone. It passes superiorly and posteriorly to insert into the lateral half of the inferior nuchal line on the external surface of the occipital bone. The muscle is innervated by the suboccipital nerve, the dorsal ramus of the first spinal nerve. It acts at the atlanto-occipital joint to extend the head and flex the head to