Which roots of the spinal nerve are responsible for motor output?

The ventral roots of the spinal nerve are responsible for motor output because they contain the axons of motor neurons that transmit signals from the spinal cord to the skeletal muscles. This pathway allows the central nervous system to control voluntary movements. When the motor neurons in the ventral horn of the spinal cord are activated, they send electrical impulses down their axons that exit the spinal cord through the ventral roots.

In contrast, the dorsal roots carry sensory information from the body to the spinal cord, which is why they do not contribute to motor output. The cauda equina refers to the collection of spinal nerves that extend below the end of the spinal cord; while it performs essential neural functions, this structure is not primarily associated with producing motor signals. Spinal rami are the branches of spinal nerves that emerge after the spinal nerve exits the vertebral column and may carry both motor and sensory fibers, but they do not serve as the origin of motor output on their own.