Motor nerve

Motor nerves carry information from the central nervous system to the muscles. The signals for this originate in the motor area of the cerebrum. These signals descend via the cerebellum and the brainstem to the spinal cord. The cell body of a motor nerve remains in the central nervous system; via a long projection, it finally reaches the muscle.

To be able to make a movement, muscles must receive the command to do so. That control occurs via the brain and motor nerves. The senses have perceived stimuli from the environment. They pass these signals via sensory nerves to the central nervous system. The central nervous system then sends signals to the muscles to take action.

For example, to drive a nail into a plank. First, our senses, such as the eyes, have explored the environment. The sensory nerves in the arm know where the arm is at that moment and send this information to the brain. The brain processes the signal into a movement in which, via motor nerves, the appropriate muscles are contracted. The result: deliberately reaching for the hammer, lifting it, and striking the nail with exactly the right force.

This is the voluntary component of the motor nerves. However, these nerves also play a role in the body's involuntary movements. By this we mean the unconscious actions, such as contracting the heart muscle at the right moment. This happens completely automatically. It is impossible to generate a signal in the brain that travels via the motor nerve to the heart to stop it or make it work harder.

The motor cortex in the cerebrum consists of a left and a right half. The nerve tracts that originate here cross before they enter the spinal cord. This crossing ensures that, in people with a stroke in the right hemisphere of the brain, the left side of the body is affected.