College of Massage Therapists of British Columbia (CMTBC) Practice Exam

How do motor neuron impulses enter the ipsilateral spinal cord?

1. Through sensory neuron pathways

2. Through peripheral nerves

3. Directly from the brain

4. They do not enter

The correct answer is: Through peripheral nerves

Motor neuron impulses enter the ipsilateral spinal cord through peripheral nerves. Peripheral nerves are part of the peripheral nervous system, which connects the central nervous system to the limbs and organs. They carry motor signals from the motor neurons, which originate in the brain and spinal cord, to their target muscles. When a motor neuron is activated, its impulses travel down the axon and through the peripheral nerves that lead into the spinal cord. Once they reach the spinal cord, these impulses help facilitate movement by synapsing with lower motor neurons located in the anterior horn of the spinal cord, which then relay the signals to skeletal muscles. The other options do not accurately describe the pathway of motor neuron impulses. Sensory neuron pathways are involved in transmitting sensory information to the central nervous system rather than motor signals. While some impulses originate directly from the brain, they still travel through peripheral nerves to reach the muscles. Lastly, the idea that motor neuron impulses do not enter the spinal cord contradicts established knowledge about motor function and reflex arcs.