Final answer:
When 2.0 volts is applied to a muscle with a threshold of 1.0 volt, it does not create a larger action potential but may cause action potentials to occur more frequently; all action potentials peak at the same voltage, and are 'all or none'.
Step-by-step explanation:
If a muscle's threshold stimulus is 1.0 volt, applying 2.0 volts will not produce a "bigger" action potential, because action potentials operate on an "all or none" principle. After depolarization reaches the threshold (typically around -55 mV), an action potential is triggered and will run its course to peak at +30 mV, a process during which K+ ions cause repolarization and a subsequent hyperpolarizing overshoot. Applying a voltage higher than the threshold, such as 2.0 volts, does not create a larger action potential but can cause multiple action potentials to occur more quickly. A stronger stimulus results in a more frequent initiation of action potentials but does not affect the size or intensity of each individual action potential.