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
Digastric muscle shoulder. Likewise, we speak of the digastric even though there is a right and left digastric muscle. The posterior belly, longer than the anterior belly, arises from the mastoid notch which is on the inferior surface of the skull, medial to the mastoid process of the temporal bone. The mastoid notch is a deep groove between the mastoid process and the styloid process. The mastoid notch is also referred to as the digastric groove or the digastric fossa. The posterior belly is supplied by the digastric branch of facial nerve. The digastric muscle stretches between the mastoid process of the