| Flap 1 | Flap 2 |
| actin | thin, protein filament component of myofibril |
| ATP | chemical source for energy for body - adenosine triphosphate |
| ATPase | enzyme which splits ATP to release energy |
| fast-twitch (FT) fiber | a type of muscle fiber which is characterized by lower peak tension time and highest power |
| motor unit | a single motor neuron and muscle fibers it innervates |
| muscle fiber | another name for a muscle cell whose structure contains nucleus, mitocondria, sacroplasm and myofibril. Individual muscle cell whose size ranges from 10-80um is diameter and range up to 12cm long. |
| myofibril | contractile elements of skeletal muscle composed of sarcomeres |
| myosin | a thick protein filament composed of two protein strands, each folded into a globular head at one end |
| myosin cross-bridge | the two-headed portion of myosin filament with attachment sites for actin and ATP |
| sarcolemma | plasma membrane which surrounds the muscle fiber/cell whose ends are fused to tendons which are attached to bones |
| transverse tubules | extentions of the sarcolemma which run laterally through muscle figer. They carry nerve impulses and allow for the exchange of waste products in the fiber. |
| sarcoplasmic reticulum | calcium storage area which wraps around myofibrils |
| sacroplasm | flud inside the muscle fiber composed of various organels and other cell material |
| sarcomere | basic unit of myofibril |
| slow-twitch (ST) fiber | type of muscle fiber characterized by slower peak tension time, lowest power and high aerobic endurance |
| tropomyosin | tube shaped protein which twists around the actin strand which hides the active sites during muscle relaxation |
| troponin | a complex protein which is attached at regular intervals to tropomyosin. It has an affinity for calcium ions which are released during muscle activation and this affinity results in the pulling of the troponin off the myosin’s active site ultimately resul |
| action potential | rapid and substantial depolarization of a neuron’s membrane |
| golgi tendon organ | organ of the sensory division which detects the strain of the muscle/tendon complex thereby causing muscle actions to reduce injury |
| muscle spindle | specialized muscle fibers whose function is to monitor the length of the muscle and along with sensory nerve ending communicate to the CNS to maintain the desired muscle length |
| neuromuscular junction | site where motor neurons communicate with muscle fibers |
| summation | the cumulative effect of all graded potentials by axon hillocks which potentially result in an action potential |
| synapse | site where nerve impulses are transmitted from one neuron to the next |
| neurotransmitter | chemicals stored in axon terminals of a neuron which facilitate communication to the neighboring neuron |
| depolarization | decrease of potential voltage change of a neuron’s cell membrane below the rest membrane potential (RMP = -70mV). This is used as a communication signal between cells |
