Which term describes a group of muscle cells and a motor neuron that function together to cause movement?

• A. Motor unit
• B. Myofibril
• C. Sarcomere
• D. Neuromuscular junction

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the components of the problem. The question is asking for a term that describes a group of muscle cells and a motor neuron working together to cause movement.
2. Step 2: Review the definitions of the given options: - Motor unit: A motor neuron and all the muscle fibers it innervates, functioning as a single unit to produce movement. - Myofibril: A structural component of muscle cells, composed of repeating units called sarcomeres, responsible for contraction. - Sarcomere: The smallest functional unit of a myofibril, responsible for muscle contraction. - Neuromuscular junction: The synapse where a motor neuron communicates with a muscle fiber.
3. Step 3: Analyze the question. The term must describe a functional unit involving both a motor neuron and muscle fibers working together to produce movement. This eliminates options like 'Myofibril' and 'Sarcomere,' which are structural components rather than functional units.
4. Step 4: Compare the remaining options. 'Neuromuscular junction' refers to the communication site between a motor neuron and a muscle fiber, but it does not include the group of muscle fibers themselves. 'Motor unit' includes both the motor neuron and the muscle fibers it controls, making it the correct term.
5. Step 5: Conclude that the correct answer is 'Motor unit,' as it best fits the description of a group of muscle cells and a motor neuron functioning together to cause movement.