Final answer:
Muscular force is adjusted to match increased loads by increasing the frequency of action potentials or by recruiting more and larger motor units. This process is key to muscle contraction strength and is known as recruitment. Neither recruiting fewer units nor decreasing action potential frequency is correct.
Step-by-step explanation:
Muscular force can be adjusted to match increased loads by: recruiting more motor units, increasing the frequency of action potentials in motor neurons, and recruiting larger motor units. This process is called recruitment, where the nervous system controls the contraction of a muscle by signaling more motor units for greater force demands.
The correct answer to the student's question is that muscular force can be adjusted either by increasing the frequency of action potentials in motor neurons or by recruiting more and larger motor units, not by recruiting fewer or smaller motor units.
The size of the motor units and the frequency of action potentials both play a crucial role in the force production of muscles. Larger motor units are recruited for tasks that require more strength.
Additionally, increasing the frequency of action potentials can slightly increase this force, as it leads to a greater calcium concentration in the sarcoplasm, which then leads to more myosin-actin cross-bridges during muscle contraction.