Final answer:
Alpha motor neurons are faster than gamma motor neurons and crucial for the contractile force for movement. They transmit signals from the spinal cord to the skeletal muscles, facilitating rapid and powerful contractions.
Step-by-step explanation:
Alpha motor neurons conduct signals faster than gamma motor neurons and are responsible for the contractile force that moves the skeleton.
Muscle contraction is a process that involves both upper motor neurons (UMN) and lower motor neurons (LMN). The UMN's role is to carry signals from the brain to the spinal cord. The LMN, specifically alpha motoneurons, directly control skeletal muscle contraction. They originate from the ventral horn of the spinal cord, carrying signals through their axons in the nerves to innervate muscle fibers at neuromuscular junctions. The speed of signal conduction is facilitated by the myelin sheath that coats the axon, allowing rapid action potential propagation for quick muscle response. This system is especially important for movements requiring powerful contractions like those performed by the quadriceps, where precision is less of a focus, compared to muscles controlling eye movement where precision is critical.
Lower motor neurons conduct signals faster than upper motor neurons and are responsible for the contractile force that moves the skeleton.
The motor neurons that control skeletal muscles originate in the spinal cord and brainstem. They have long axons that transmit action potentials from the CNS to the muscles. These axons bundle together to form nerves.
The number of muscle fibers innervated by a single motor neuron varies based on the precision and force required for a specific muscle. For example, the quadriceps have many fibers controlled by a single motor neuron for powerful, non-precise contractions, while the extraocular muscles have fewer fibers per motor neuron for precise movements of the eyes.