​​Complaining of muscle weakness, Delia goes to the doctor. Devise a series of physical examination tests that would help to determine if her problem involves upper or lower motor neurons.

Video transcript

Hi, everyone. Welcome back. Our next question says, choose which statement describes the correct function of upper motor neurons. A upper motor neurons transmit impulses via spinal peripheral nerves or cranial nerves to skeletal muscles. B upper motor neurons directly innervate skeletal muscle and have cell bodies in the anterior horn of the spinal cord or c. A unique characteristic of the upper motor neuron lesions. Is there tendency to affect specific muscle groups or d all of the above? So to answer this question, we need to remember the distinction between upper motor neurons and lower motor neurons. So upper motor neurons have their cell bodies. Are there cell bodies in the cerebral cortex where they then send messages to the brain stem or the spinal cord where they synapse with the lower motor neurons. So that's the upper motor neuron. Whereas lower motor neurons have their cell bodies in the brain stem or spinal cord where they then enervate a single muscle unit in a skeletal muscle. So that's the lower motor neuron. So we've got upper motor neurons going from the cerebral cortex to the brain stem or spinal cord where then the lower motor neurons carry the message to the muscles. So with that in mind, let's look at our answer. Choices. Choice say says upper motor neurons transmit impulses via spinal peripheral nerves or cranial nerves to skeletal muscles. Well, this is going to be incorrect because that is lower motor neurons. So they carry the impulses directly to the skeletal muscles. And that would be via those spinal peripheral nerves or cranial nerves. Choice b upper motor neons directly enervate skeletal muscle and have cell bodies in the anterior horn of the spinal cord. Again, that's going to be lower motor neurons. So choice B is incorrect. Then that means we can also rule out choice D all of the above and by process of elimination, we have choice C as our answer, a unique characteristic of upper motor, upper motor neuron lesions is their tendency to affect specific muscle groups. Well, this obviously is true of actually both upper and motor lower motor neuron lesions because they do as we said, eventually, that message gets carried to a single muscle unit. So damage to one of these upper motor neuron lesions will affect the muscle group that the message eventually gets sent to, gets sent to down the line. So again, the statement that describes correctly, the function of upper motor neurons is choice C that a characteristic of upper motor neuron lesions is their tendency to affect specific muscle groups. See you next video.