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 lower motor neurons in the nervous system, which are responsible for directly innervating skeletal muscle fibers to cause contraction.
2. Recall that α-motor neurons are a type of lower motor neuron that specifically innervate extrafusal muscle fibers, which are the main contractile fibers of the muscle.
3. Consider the function of β-motor neurons, which are less commonly discussed and primarily involved in innervating intrafusal fibers within muscle spindles.
4. Differentiate upper motor neurons from lower motor neurons, as upper motor neurons originate in the brain and communicate with lower motor neurons to initiate movement.
5. Recognize that γ-motor neurons innervate intrafusal muscle fibers, adjusting the sensitivity of muscle spindles, rather than directly causing muscle contraction.

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 and reflexive movements. Understanding their role is crucial for grasping how motor control is 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 understanding muscle physiology.

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, contributing to proprioception. Familiarity with these distinctions helps clarify the roles of various motor neurons in muscle control and reflexes.