Final answer:
A normal infant shows good muscle tone with flexed limbs that resist extension, demonstrating neurological development and physical readiness for developmental milestones. Conditions such as hypotonia and hypertonia signify abnormal muscle tone, either too low or too high, respectively, which can indicate underlying health issues.
Step-by-step explanation:
A normal infant typically demonstrates good muscle tone by having flexed arms and legs that resist extension to some degree. Healthy muscle tone is crucial for newborns, as it shows proper neurological development and physical strength needed for early developmental milestones, such as rolling over and holding the head up. In medical evaluations like the Apgar score, muscle tone is one of the five criteria assessed. Newborns with normal muscle tone present with certain reflexes like the rooting reflex that are crucial to survival, and they tend to maintain a flexed posture that gradually unfolds over the first few months as they gain more control over their movements.
It's also important to distinguish between normal muscle tone and conditions like hypotonia or hypertonia, which can indicate underlying neurological or muscular issues. Hypotonia is characterized by a lack of resistance to passive movement, while hypertonia involves excessive muscle tone. A healthcare provider can assess an infant's muscle tone during regular check-ups to ensure that they are developing as expected.