What is meant by upper motor neuron & lower motor neuron?

Upper motor neuron: A neuron that starts in the motor cortex of the brain and terminates within the medulla (another part of the brain) or within the spinal cord. Damage to upper motor neurons can result in spasticity and exaggerated reflexes. There is no standard laboratory test for upper motor neuron disease. read more

Upper motor neuron: A neuron that starts in the motor cortex of the brain and terminates within the medulla (another part of the brain) or within the spinal cord. Damage to upper motor neurons can result in spasticity and exaggerated reflexes. read more

Since the upper motor neurons (spinal-cord nerves controlling movement) and lower motor neurons (nerves that leave the cord to connect to muscles) use different neurotransmitters (chemicals released from a neuron ending that interact with an adjacent neuron or muscle cell), gene research should provide more definitive information on this function-restoring procedure's mechanism of action. read more

At this point, the upper motor neuron synapses with the lower motor neuron, each of whose axons innervate a fiber of skeletal muscle. These neurons connect the brain to the appropriate level in the spinal cord, from which point nerve signals continue to the muscles by means of the lower motor neurons. read more