Term | Definition |
Origin | The attached end of a skeletal muscle that remains relatively stationary. |
Insertion | The attached end of a skeletal muscle that attaches to another bone ACROSS a joint. |
Myofibril | Long cylindrical structures packed with actin and myosin, arranged in parallel within a muscle cell. |
Sarcomere | A segment of a myofibril from one Z-line to the next. |
Actin and Myosin | Muscle proteins that alternate within a myofibril. |
Motor Neuron | Nerve cell that stimulates a muscle cell to contract. |
Neuromuscular Junction | The intersection between motor neuron and skeletal muscle cell. Acetylcholine is the neurotransmitter released into this space. |
Sarcoplasmic Reticulum | Similar to the Smooth ER, this is series of membrane bound chambers that store Ca+ ions. |
Sliding Filament Mechanism | Sarcomeres shorten when the thick and thin filaments slide past each other in order to produce a contraction. |
Oxygen debt | After exercise, extra oxygen is required to metabolize lactic acid produced by anaerobic respriation. |
Creatine Phosphate | A temporary storage molecule of phosphorus beyond ATP. |
Motor Unit | The motor neuron and all of the muscle cells it controls. |
All or None Principle | Describes how muscle cells always respond with a complete cycle of contraction and relaxation (twitch). |
Recruitment | Activation of more motor units as strain or intensity increases. (More motor neurons) |
Summation | Increasing muscle cell force by increasing the rate of stimulation of motor units. (Rate of stimulation) |
Muscular Dystrophy | Genetic disorder that decreases muscular strength. |
Tetanus | Bacterial infection. Toxin causes sustained muscular contraction. |