Final answer:
The tension in skeletal muscle depends on motor unit activation, stimulation frequency, and the length-tension relationship, which affect cross-bridge formation and the force of contraction.
Step-by-step explanation:
The amount of tension developed by a whole skeletal muscle depends on three main factors: the number of motor units activated, the frequency of stimulation, and the length-tension relationship of the muscle fibers. Firstly, each motor unit consists of a motor neuron and the muscle fibers it innervates. The more motor units that are activated, the greater the force produced due to more muscle fibers contracting. Secondly, the frequency of stimulation can lead to summation and tetanus, which increase tension by allowing less time for muscle relaxation between stimuli. Lastly, the length-tension relationship is crucial because it determines how the sarcomere length affects tension. An optimal length allows the maximum number of cross-bridges to form, leading to the most substantial force generation.
Muscle fibers produce tension by forming cross-bridges between actin and myosin, and the force of contraction correlates with the number of cross-bridges. Hormones, stress, and exercise can induce muscle hypertrophy, increasing the number of myofibrils and sarcomeres, and consequently affecting the tension produced. Conversely, atrophy from disuse or disease leads to a decrease in these structures, reducing tension.