| Motor unit | a motor neuron and all the muscle fibers it innervates |
| Motor pool | all individual neurons that innervate a single muscle |
| Tetanus | a sustained muscle contraction |
| Iso | a root word that means "same" |
| Isometric | a muscle contraction in which there is no change in length |
| Isotonic | a muscle contraction in which there is no change in tension |
| Isometric | a muscle contraction that increases in tension |
| Isotonic | a muscle contraction in which the muscle shortens |
| Slow twitch | muscle fibers that appear red in color |
| Fast twitch | muscle fibers that appear white in color |
| Slow twitch | muscle fibers used for endurance |
| Fast twitch | muscle fibers used for powerful contractions |
| Slow twitch | muscle fibers rich in myoglobin and capillaries |
| Fast twitch | muscle fibers that have to ferment after a short period |
| Myoglobin | protein that gives muscles its red appearance |
| Lactic acid | acid produces by fermenting muscle cells |
| Fermentation | type of metabolism muscle use when oxygen is absent |
| Cori cycle | the recycling of lactic acid from muscles and glucose from liver |
| Somatic senses | senses located throughout the body |
| Proprioception | perception of the position & movement of the body |
| Golgi tendon organ | stretch receptor located in tendons |
| Muscle spindle | stretch receptor located in muscles |
| Stretch receptor | sensory neurons that signal when distended |
