Final answer:
Interneurons primarily function to integrate signals within the spinal cord during movement, forming critical links between sensory inputs and motor outputs to facilitate coordinated movement.
Step-by-step explanation:
The primary function of interneurons during movement is integrating signals within the spinal cord. Interneurons act as a link between sensory inputs and motor outputs, helping the central nervous system (CNS) process information. For instance, when a neuron in the spinal cord receives touch information, it then transmits that information to another spinal cord neuron that controls the movement of an arm muscle. This is a key step in the neural pathway leading to movement, as it allows the CNS to make coordinated responses.
Specifically, interneurons carry nerve impulses back and forth, often between sensory neurons, which carry information toward the CNS, and motor neurons, which carry information away from the CNS to muscles. Therefore, during movement, a neuron in the cerebral cortex of the brain might fire a nerve impulse sent to an interneuron in the spinal cord, which in turn sends the signal through a motor neuron to a muscle, causing the muscle to contract.