Upper motor neurons are nerve cells located in the brain and spinal cord that send signals to lower motor neurons. They play a crucial role in controlling voluntary movements by transmitting messages from the brain to the spinal cord, which then communicates with muscles. Damage to upper motor neurons can lead to various motor disorders, such as spasticity and muscle weakness. Conditions like multiple sclerosis and stroke can affect these neurons, resulting in impaired movement and coordination. Understanding upper motor neurons is essential for diagnosing and treating neurological conditions.