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Anatomy Unit 5
Muscle Contractions
| Term | Definition |
|---|---|
| sliding filament mechanism | muscle shortens because thick and thin filaments slide past each other |
| contraction cycle | repeated cycle of pulling |
| ATP hydrolysis, attachment of myosin and actin, power stroke, detachment of myosin and actin | Phases of contraction cycle |
| ATP hydrolysis | reorients and energizes myosin head; ATP binding site and ATPase |
| Attachment of myosin and actin | releases the phosphate group; cross bridges |
| power stroke | ADP is released, cross bridge rotates, rotation generates force, and slides the action toward M line |
| Detachment of Myosin and Actin | Myosin stays bound to actin until ATP binds; ATP binds to myosin head, Myosin detaches from actin |
| Excitation-Contraction coupling | Ca2 the start of contraction, Ca2 stored in sarcoplasmic reticulum, muscle action potential, Ca2 binds to troponin |
| Rigor Mortis | following death; ATP synthesis stops so head can't detach, making the muscle rigid |
| Excitation | muscle action potential |
| Contraction | sliding of filaments |
| Length-Tension relationship | force dependent on sarcomere length before a contraction |
| overstretched | fewer myosin heads can bind actin; no overlap, no tension; at around 170% of optimal length |
| understretched | thick filaments crumple against Z discs |
| Neuromuscular Junction | synapse between motor neuron and muscle fiber; where the muscle action potential begins |
| somatic motor neurons | stimulate skeletal muscle fiber contractions |
| muscle action potentials | propagate along sarcolemma |
| synaptic cleft | gap between axon terminal and sarcolemma |
| neurotransmitter | chemical communication across synaptic cleft |
| synaptic end bulb | swollen end of axon terminal |
| synaptic vesticles | sacs in synaptic end bulb that contain acetylcholine (ACh) |
| acetylcholine | neurotransmitter; crosses synaptic cleft |
| motor end plate | muscle fiber site of NMJ (30-40 million ACh receptors) |
| Acetylcholine receptors | transmembrane ligand-gated ion channels |
| junction folds | grooves; increase surface area |
| release acetylcholine, activation of ACh receptors, production of muscle action potential, termination of ACh activity | steps of action potential |
| nerve impulse, acetylcholine, muscle action potential, sarcoplasmic reticulum, troponin-tropomyosin, contraction, relaxation | order of muscle contraction |
| Muscle Metabolism | huge amounts of ATP required for muscle contractions; only enough ATP in cells for few seconds |
| creatine phosphate | relaxed fibers produce excess ATP; fastest and used first |
| creatine | small amino acid-like molecule synthesized in the liver, kidneys, and pancreas |
| Anaerobic Glycolysis | glucose catabolized for ATP; 2 ATP per glucose; lactic acid is created |
| glycolysis | glucose turns to pyruvic acid and 2 ATP are released |
| lactic acid | carried to the liver; muscle soreness |
| aerobic respiration | glucose turns to pyruvic acid and 30-32 ATP are produced; oxygen in the form of hemoglobin or myoglobin |
| relaxed muscle | very low Ca2 in sarcoplasm (0.1 umol/L) |
Created by:
auweb921
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