Stimulation of a muscle fiber by a motor neuron occurs at
The neuromuscular junction
The neuron that transmits a stimulus to muscle tissue is called a motor neuron. A motor unit consists of a single motor neuron (nerve cell) and muscle fibers it innervates. The portion of the muscle plasma membrane (sarcolemma) that lies beneath the nerve endings (axon terminals) is called the motor end plate. The axon terminals and the motor end plate together constitute the neuromuscular junction or the neuromotor junction.
The primary duty of transverse tubules, or T-tubules, is to allow the conduction of electrical impulses.Transverse tubules exist as invaginations of the sarcolemma.
Muscles are composed of tubular cells called myocytes, known as muscle fibers in a striated muscle, and these cells, in turn, contain many chains of myofibrils.
The sarcoplasmic reticulum is a specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells.