Order: 200 mg IM. Available: 100 mg/mL. How many mL will the nurse give?

31 Step 1 is 200 mg ÷ 100 mg/mL = 2 mL.

Choice A rationale

While the loss of voluntary movement, or paralysis, can occur in both upper and lower motor neuron lesions, it is not the most specific or defining characteristic of a UMN injury. UMN lesions occur in the brain or spinal cord, affecting the descending motor pathways. Although voluntary control is lost, the reflexive arcs remain intact and often become overactive because the inhibitory influence from the primary motor cortex is removed by the injury.

Choice B rationale

Upper motor neuron lesions are characterized by spasticity, which is an increase in muscle tone, and hyperreflexia, which is exaggerated deep tendon reflexes. This occurs because the UMNs normally provide inhibitory signals to the lower motor neurons in the spinal cord. When the UMN pathway is damaged, such as in a stroke or spinal cord injury, the LMNs become hyper-excitable. This results in the classic clinical presentation of increased resistance to passive stretch and hyperactive reflexes.

Choice C rationale

Progressive muscle atrophy and fasciculations are hallmark signs of a lower motor neuron (LMN) lesion, not an upper motor neuron lesion. LMNs are the final common pathway connecting the central nervous system to the muscles. When these neurons are damaged, the muscle loses its trophic support and nerve stimulation, leading to significant wasting and spontaneous twitching of muscle fibers. In contrast, UMN lesions typically cause minimal disuse atrophy and no fasciculations.

Choice D rationale

Hyporeflexia, which refers to diminished reflexes, and decreased muscle tone, or flaccidity, are classic indicators of a lower motor neuron lesion. This occurs because the reflex arc is physically interrupted at the level of the peripheral nerve or the anterior horn cell of the spinal cord. In an acute UMN injury, such as spinal shock, there may be temporary flaccidity, but the long-term consistent finding of a UMN lesion is the development of hypertonicity.