(2) A motor neuron in the ventral horn of the spinal cord is activated, and an action potential passes outward in a ventral root of the spinal cord. (3) The axon branches to supply a number of muscle fibers called a motor unit, and the action potential is conveyed to a motor end plate on each muscle fiber.
The average male height varies from country to country. The estimated average height for the human male across the world is approximately 5ft 8 1/2in (1.73 m.) According to John Komlos of the University of Munich, North Americans were the tallest people on the planet from about the American Revolution to World War II.
Through history human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average mass of an adult human is 54â64 kg (120â140 lbs) for females and 76â83 kg (168â183 lbs) for males.