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.
The threshold of sensation for humans is one milliamp (1mA), while a sustained current of 200mA is fatal-able to stop a typical human heart weighing around 300g. According to Ohm's Law, current passing through a conductor is given by voltage divided by electrical resistance, measured in ohms. The resistance of human skin varies between 1,000 ohms (wet skin) to 100,000 (dry), so the lethal voltages are 200V and 20,000V respectively. A 400g heart (the most a healthy heart can weigh) might take up to 27,000V. At high voltages, extra physics comes into play.