Final Answer:
The rapid muscle atrophy observed in skeletal muscles is a consequence of decreased activity and certain health conditions, leading to a reduction in both the number and size of muscle cells. Although exercise can mitigate atrophy to some extent, age-related sarcopenia is irreversible. Unlike involuntary smooth muscles, skeletal muscles are significantly affected by sedentary lifestyles, exacerbating muscle loss.
Step-by-step explanation:
Prolonged inactivity in skeletal muscles results in rapid muscle atrophy, characterized by a decrease in both the number and size of muscle cells, accompanied by reduced protein content. Physical inactivity, as seen in bedridden patients or astronauts in space, induces weakening and atrophy of muscles.
Conditions such as cachexia related to cancer and AIDS, congestive heart failure, and liver diseases can also contribute to skeletal muscle atrophy. Additionally, aging leads to sarcopenia, an irreversible loss of muscle mass and strength, exacerbated by sedentary lifestyles. While exercise can partially counteract atrophy effects, sarcopenia represents an inevitable aspect of aging, involving muscle fiber reduction and replacement by connective and adipose tissues.
The distinct response to a sedentary lifestyle between skeletal and smooth muscles arises from their varied functions and fiber types. Skeletal muscles, being voluntary, are prone to atrophy when not regularly engaged, while involuntary smooth muscles found in organs and blood vessels are less influenced by changes in physical activity levels.