If all of the muscle fibers in the neck, trunk, and legs were to totally relax, the body would collapse. What is the state called where some of the fibers in a particular muscle are always contracted?

A) twitch
B) threshold
C) tetanus
D) tone
E) summation

The state where some of the fibers in a particular muscle are always contracted is called muscle tone. This is necessary to maintain posture and prevent the body from collapsing. Choice A (twitch) refers to a single contraction-relaxation cycle of a muscle fiber. Choice B (threshold) refers to the minimum stimulus needed to elicit a muscle or nerve response. Choice C (tetanus) refers to a sustained contraction of a muscle fiber due to high-frequency stimulation. Choice E (summation) refers to the increased force of a muscle contraction when a second stimulus is applied before the muscle has fully relaxed from the previous stimulus.