Questions: The junction between a motor neuron's axon and the muscle fiber plasma membrane is called a junction. A motor neuron and all of the skeletal muscle fibers it stimulates is called a 2 The actual gap between the axon terminal and the muscle fiber is called a Within the axon terminal are many small vesicles containing a neurotransmitter substance called When the and diffuses the axon, the neurotransmitter is released The combining the muscle cell membrane to combine with receptors there. causes a change of the neurotransmitter with the muscle membrane receptors sarcolemma of the The events that occur at a neuromuscular junction are depicted below. Identify every structure provided with a leader line. Key: a. axon terminal of motor neuron b. motor neuron axon branch c. myelinated axon of motor neuron d. muscle fiber e. sarcolemma of muscle fiber f. synaptic cleft g. Synaptic vesicle containing ACh h. terminal cistern of the SR i. triad

Solution Steps

1. neuromuscular: The junction between a motor neuron's axon and the muscle fiber plasma membrane is called a _neuromuscular_ junction.
2. motor unit: A motor neuron and all of the skeletal muscle fibers it stimulates are called a _motor unit_.
3. synaptic cleft: The actual gap between the axon terminal and the muscle fiber is called a _synaptic cleft_.
4. acetylcholine (ACh): Within the axon terminal are many small vesicles containing a neurotransmitter substance called _acetylcholine_.
5. action potential: When the _action potential_ reaches the end of the axon, the neurotransmitter is released.
6. depolarization: Combining the neurotransmitter with muscle membrane receptors causes a change in the permeability of the membrane, resulting in _depolarization_ of the sarcolemma.

a. axon terminal of motor neuron: The bulbous end of the axon where it meets the muscle fiber. b. motor neuron axon branch: The branches extending from the main axon, leading to the axon terminals. c. myelinated axon of motor neuron: The portion of the axon covered in myelin sheath, preceding the branches. d. muscle fiber: The elongated cell making up the muscle tissue. e. sarcolemma of muscle fiber: The plasma membrane of the muscle fiber. f. synaptic cleft: The gap between the axon terminal and the muscle fiber. g. synaptic vesicle containing ACh: The small vesicles within the axon terminal containing acetylcholine.

d. muscle fiber: The elongated cell making up the muscle tissue. e. sarcolemma of muscle fiber: The plasma membrane of the muscle fiber. h. terminal cistern of the SR: The enlarged portion of the sarcoplasmic reticulum near the T tubules. i. triad: The structure formed by a T tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. j. T tubule: The invagination of the sarcolemma that penetrates deep into the muscle fiber.

Final Answer: