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The space between neurons that share a functional connection.
Neurons that control effectors, including skeletal muscle fibers.
The synapse where a motor neuron axon and a skeletal muscle fiber meet.
Specialized portion of the muscle cell membrane that is extensively folded.
Motor End Plate
A small gap that separates the membrane of the neuron and the membrane of the muscle fiber.
A motor neuron and the muscle fibers it controls.
The neurotransmitter that motor neurons use to control skeletal muscle contraction.
A chain of action potentials that ultimately reaches the sarcoplasmic reticulum and triggers the release of calcium ions which leads to muscle contraction.
A muscle impulse responds at full speed, full strength, or it doesn’t respond at all, this is according to what?
When a muscle fiber becomes excited by the rising concentration of calcium in the cytosol, and the calcium binds to the troponin of the actin, changing its shape, and opening actin binding sites for the myosin heads to bind to, creating cross-bridges.
Excitation Contraction Coupling
According to the ______ of muscle contraction, when sarcomeres shorten, the thick and thin filaments slide past one another.
Sliding Filament Model
These pull on actin filaments to shorten sarcomeres; formed when a myosin head attaches to an actin binding site.
Enzyme found in myosin heads that catalyzes the breakdown of ATP into ADP and phosphate, releasing energy for contraction.
Enzyme that decomposes ACh so the action potentials can no longer reach the axon terminal and the muscle fiber becomes relaxed.
What is the role of calcium in muscle contraction?
Calcium binds to the troponin, changing the actin filament’s shape, so it can bind to the myosin heads to form cross-bridges; without calcium, the actin binding sites are unavailable, and the contraction cycle cannot occur.
What is the role of ATP in muscle contraction?
ATP is required for the cross-bridge cycle; after the cross-bridges pulls the actin filament, ATP binds to myosin, releasing the linkages, the breakdown of that ATP puts the myosin heads in a “cocked” position, then it attaches to another binding site further down the actin filament and pull again.
What is the role of ATP in muscle relaxation?
ATP is required for the calcium pump to actively transport calcium from the cross-bridge linkages back into the sarcoplasmic reticulum, and when calcium is removed from the cross-bridge linkages, the actin binding sites are unavailable, and the contraction cycle cannot occur.
The initial energy source available to regenerate ATP from ADP and phosphate; after it’s used, a muscle cell must depend on cellular respiration of glucose to synthesize ATP.
Reddish-brown pigment that stores oxygen in muscle tissue so it is available to support the aerobic reactions of cellular respiration in the mitochondria.
Give two reasons why oxygen storage in muscle tissue is important.
1) Oxygen is needed to support the aerobic reactions of cellular respiration when the muscle fibers need ATP to be regenerated. 2) Oxygen storage reduces a muscle’s requirement for continuous blood supply because during contraction, blood flow may decrease when contracting muscle fibers compress blood vessels
The shift in cellular metabolism from breaking down pyruvic acid into CO2 to breaking down pyruvic acid to form lactic acid, so it can be carried to the liver and converted into glucose.
Lactic Acid Threshold
The amount of oxygen the liver requires to use the accumulating lactic acid to produce glucose, plus the amount of oxygen the muscle cells require to resynthesize ATP and creatine phosphate to restore their original concentrations; it occurs as lactic acid accumulates and must be repaid later.
A condition in which a muscle fiber cannot contract.
List the 4 causes of muscle fatigue.
1) Decreased blood flow. 2) ion imbalances across the sarcolemma. 3) Loss of desire to continue exercise. 4) The accumulation of hydrogen ions due to lactic acid formation (the lowered pH from the lactic acid prevents muscle fibers from responding to stimulation)
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