The lower motor neurons that innervate contractile skeletal muscle fibers are called:
a. α-motor neurons
b. β-motor neurons
c. upper motor neurons
d. γ-motor neurons

Verified step by step guidance

1. Understand the role of motor neurons: Motor neurons are responsible for transmitting signals from the central nervous system to muscles, causing them to contract. They are divided into upper motor neurons and lower motor neurons.
2. Differentiate between upper and lower motor neurons: Upper motor neurons originate in the brain and send signals to lower motor neurons. Lower motor neurons directly innervate skeletal muscle fibers to cause contraction.
3. Learn about the types of lower motor neurons: Lower motor neurons are further classified into α-motor neurons, β-motor neurons, and γ-motor neurons, each with specific functions.
4. Focus on α-motor neurons: α-motor neurons specifically innervate extrafusal muscle fibers, which are the contractile fibers of skeletal muscles responsible for generating force.
5. Eliminate incorrect options: β-motor neurons innervate intrafusal fibers and are involved in muscle spindle sensitivity. γ-motor neurons also innervate intrafusal fibers to adjust spindle tension. Upper motor neurons do not directly innervate skeletal muscle fibers. Therefore, the correct answer is α-motor neurons.

Key Concepts

Lower Motor Neurons

Lower motor neurons are the neurons that directly innervate skeletal muscle fibers, facilitating muscle contraction. They originate in the spinal cord and extend to the muscles, transmitting signals that lead to voluntary movements. Understanding their role is crucial for identifying how motor commands are executed in the body.

α-Motor Neurons

α-motor neurons are a specific type of lower motor neuron responsible for innervating extrafusal muscle fibers, which are the primary contractile units of skeletal muscles. They play a vital role in generating force and movement by transmitting action potentials that lead to muscle contraction. Recognizing their function is essential for answering questions about muscle innervation.

Motor Neuron Types

Motor neurons can be categorized into different types, including α-motor neurons, β-motor neurons, and γ-motor neurons. Each type has distinct functions; for instance, γ-motor neurons innervate intrafusal fibers in muscle spindles, while β-motor neurons are involved in modulating muscle tone. Understanding these distinctions is important for comprehending the overall motor control system.