Myosin not only binds to actin, but is also an enzyme that hydrolyzes ATP to ADP. Which of the following is false? An action potential in the muscle cell activates contraction by releasing Ca2+ within the muscle. A single action potential at the neuromuscular junction is sufficient to cause a muscle to twitch. Summation of twitches is an "all-or-none" phenomenon that occurs in a single muscle fiber. The tension generated by a muscle can be varied by controlling how many of its motor units are active.

Summation of twitches is an "all-or-none" phenomenon that occurs in a single muscle fiber

Explanation:

The all-or-none principle states that the strength at which the nerve or muscle fiber responds to a stimulus is not dependent on the strength of the stimulus.

In a summation of twitches, the tension of the muscle increases with each twitch. Therefore as the action potential increases its firing, the muscle contraction increases, thus increasing muscle tension.

explanation:

the universal gravitation equation. since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. if the mass of one of the objects is doubled, then the force of gravity between them is doubled.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.