An era is a commonly used word for a long period of time. When used in science, for example geology, an era denotes a clearly defined period of time of arbitrary but well-defined length, such as for example the Mesozoic Era from 252 Maâ66 Ma, delimited by a start event and an end event.
As you increase voltage to the muscle describe how it responds to the increased stimulus. As the voltage was increased from threshold to maximum voltage, there was a greater force in the muscle contraction. Once the maximum voltage (2500 mv) was reached, even if there was an increase in voltage, the force of the muscle contraction remained the same.
If a brief stimulus is applied to the muscle or a single stimulus is applied to the nerve, a single action potential will be elicited in the muscle and, after an activation delay of about 5 msec, the muscle will contract. The time-course of this contraction, called a twitch contraction, is shown in Figure 14-12B. The tension in the muscle rises rapidly to a maximum, about 50-80 msec after the stimulus and then returns to resting tension over the next 100-200 msec or so, depending upon the particular muscle.