What is a motor unit composed of?

• A. A single muscle fiber and its associated blood vessels
• B. A single motor neuron and all the muscle fibers it innervates
• C. A group of muscle fibers and their surrounding connective tissue
• D. Multiple motor neurons and a single muscle fiber

Answer: (B)

Verified step by step guidance

1. Begin by understanding the concept of a motor unit in the context of muscle physiology. A motor unit is the fundamental unit of muscle contraction and is crucial for understanding how muscles work.
2. A motor unit is composed of a single motor neuron and all the muscle fibers it innervates. This means that one motor neuron can control multiple muscle fibers, allowing for coordinated muscle contraction.
3. The motor neuron sends electrical signals, known as action potentials, to the muscle fibers. These signals trigger the muscle fibers to contract, resulting in muscle movement.
4. Each motor unit can vary in size, with some controlling only a few muscle fibers and others controlling hundreds. The size of the motor unit is related to the precision of movement required; smaller motor units are involved in fine motor control, while larger units are used for gross movements.
5. Understanding the composition and function of motor units is essential for comprehending how muscles generate force and how different types of movements are controlled by the nervous system.