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
Procerus muscle downwards, which assists in flaring the nostrils. It can also contribute to an expression of anger. Procerus is supplied by temporal and lower zygomatic branches from the facial nerve. A supply from its buccal branch has also been described. Its contraction can produce transverse wrinkles. Procerus muscle The procerus muscle (or pyramidalis nasi) is a small pyramidal slip of muscle deep to the superior orbital nerve, artery and vein. "Procerus" is Latin, meaning tall or extended. The procerus arises by tendinous fibers from the fascia covering the lower part of the nasal bone and upper part of the lateral nasal