Question

A motor unit consists of

A) one neuron and all the skeletal muscle fibers it controls.
B) one skeletal muscle fiber and all the neurons that control that fiber.
C) one skeletal muscle fiber and the neuron that controls that fiber.
D) one axon terminal branch and the myofibrils it controls.

Answer 1

A motor unit consists of one neuron and all the skeletal muscle fibers it controls. Small motor units enable fine motor control, while large motor units allow for powerful but less precise movements.

Step-by-step explanation:

A motor unit consists of one neuron and all the skeletal muscle fibers it controls. Each muscle fiber is innervated by only one motor neuron, which allows for precise control of muscle movements. The size of a motor unit varies based on the specific muscle and its need for control and force.

For example, the extraocular eye muscles that move the eyeballs have small motor units with a single motor neuron supplying a small number of muscle fibers. This allows for fine motor control of eye movements. On the other hand, the quadriceps have large motor units with a single motor neuron supplying a large number of muscle fibers, enabling powerful contractions that do not require precision.

The neurotransmitter acetylcholine is degraded after binding to its receptor to ensure proper termination of muscle contractions.