Final answer:
The rhythmic, quivering, purposeless skeletal muscle movements described in the question are known as tremors, which are different from spasms, myoclonus, and chorea.
Step-by-step explanation:
Rhythmic, quivering, purposeless skeletal muscle movements are best described as tremors. Tremors are involuntary, rhythmic muscle contractions that cause shaking movements in one or more parts of the body. They are commonly associated with neurological conditions but can also occur as a temporary condition. Options such as spasms, myoclonus, and chorea also describe different kinds of involuntary movements, but they do not capture the rhythmic nature of the movements being asked about in the question. For example, chorea refers to sudden, rapid, jer ky movements that are not rhythmic or repetitive, and myoclonus refers to sudden muscle je rks. Hypotonia refers to reduced muscle tone, and hypertonia refers to increased muscle tone, with conditions like Parkinson's disease often presenting with muscle rigidity, a form of hypertonia.