Final answer:
Muscle tissue can grow larger (hypertrophy) or smaller (atrophy), with hypertrophy being enhanced by nutrition and regular exercise, and atrophy being caused by aging, inactivity, or disease.
Step-by-step explanation:
Muscles are continuously built up throughout life with new muscle tissue. Atrophy is when muscles break down, either because the muscles are not being used or because of disease. Factors that can cause muscle growth to be improved include nutrition and regular exercise. Conversely, muscle growth can be slowed due to aging, injury, or diseases. Muscle hypertrophy, or the growth of muscles, involves an increase in the size of muscle fibers, not the number. Exercise, such as resistance training, can lead to hypertrophy, making muscles larger and stronger.
On the other hand, muscle atrophy occurs when muscles grow smaller due to inactivity or other factors like malnutrition or disease. From an age perspective, a specific form of atrophy called sarcopenia occurs, where muscle mass and strength decline irreversibly. This highlights the importance of maintaining an active lifestyle to combat muscle loss due to aging or other causes.