| A | B |
|---|
| sarcoplasm | muscle cell cytoplasm |
| sarcolemma | plasma membrane of muscle cell |
| myofibrils | strands of muscle cells that have a striped appearance & take up most of the cell volume |
| actin | contractile protein (thin fibers) making up a myofibril |
| myosin | contractile protein (thick fibers) making up a myofibril |
| sarcomeres | found in chains, make up the myofibrils; each sarcomere contains myosin and actin arranged in a regular array |
| sarcoplasmic reticulum (SR) | system of tubules around each myofibril that releases and sequesters calcium ions |
| T tubules | invaginations of the sarcolemma that run between the terminal cisternae of the SR/ function in electrical stimulation of cells |
| sliding filament theory | the thin filaments are pulled toward the sarcomere centers by cross bridge (myosin head) activity of the thick filaments |
| troponin | protein in the thin filament that inhibits the attachment of myosin heads to actin |
| tropomyosin | a rod-shaped protein that spirals around actin and blocks the actins active site |
| cross bridge attachment | site of attachment of myosin heads to exposed binding sites on actin |
| working stroke | myosin head pivots, changing from high-energy configuration to bent, low-energy shape which pulls on thin filament |
| cross bridge detachment | ATP binds to myosin head, and actin lets go of myosin |
| "cocking" of myosin head | hydrolysis of ATP to ADP and Pi bu ATPase provides energy to return myosin to high-energy position |
| rigor mortis | death rigor (illustrates that cross bridge detachment is ATP driven, b/c cross bridge detachment is impossible and the body becomes stiff (peaks @ 12 hours) |
| action potential | electrical current needed for muscle contraction |
| motor neurons | nerves that stimulate skeletal muscles to contract |
| neuromuscular junctions | interface between the nerve and muscle cells (an axonal ending) |
| synaptic cleft | space between the end of the axon and the muscle cell (filled w/ gel-like substance of glycoproteins) |
| synaptic vesicles | small membranous sacs containing a neurotransmitter called acetylcholine (ACh) |
| motor end plate | troughlike part of the muscle fiber's sarcolemma that helps form the neuromuscular junction, have millions of ACh receptors |
| polarized | state that a resting sarcoplasmic membrane is in (negative inside the cell membrane) |
| depolarization | change in membrane potential (inside of cell membrane becomes positive) |
| repolarization | muscle returns to its polarized state |
| refractory period | period when a muscle fiber cannot be stimulated again (during repolarization) |
| all or none response | muscle fibers contract to the full extent of their ability or not at all |
| Acetylcholinesterase (AChE) | enzyme that destroys ACh so that continued contraction will not occur |
| myasthenia gravis | drooping eyelids, muscle weakness, involves a shortage of ACh receptors |
| curare | arrowhead poison (So. Amer. natives) binds to ACh receptors and blocks ACh attachment |
| myogram | apparatus that gives a graphic recording of muscle contraction |
| muscle twitch | reponse of a muscle to a single brief threshold stimulus |
| tetanus (normal) | all evidence of muscle relaxtion disappears, contractions fuse into a smooth, sustained contraction, leads to muscle fatigue |
| tetanus (bacterial disease) | causes a tetanic state to occur much longer than normal |
| muscle tone | slightly contracted state, keeps muscles firm and ready to respond, stabilizes joints, maintains posture |
| isotonic contractions | muscle changes in length and moves the load |
| isometric contractions | tension continues to increase but the muscle neither shortens nor lengthens |
| glycolysis | "sugar splitting", anaerobic stage of cellular respiration, occurs in the cell's cytoplasm, results in a net of 2 ATP |
| aerobic respiration | consists of the citric acid cycle and the electron transport chain, yields 36 ATP |
| muscle fatigue | state of physiological inability to contract (deficit of ATP) |
| contracture | state of continuous contraction (i.e. rigor mortis, or writer's cramp) |
| oxygen debt | the extra amount of oxygen that must be taken in by the body for restorative processes to occur |
| peristalsis | smooth muscle contraction (i.e. bladder) |
| gap junctions | cell connections found in smooth muscles, allow big sheet of muscle to contract as one |
| pacemaker cells | cells that signal other cells what "pace" to take when contracting |
| hyperplasia | ability of smooth muscle to divide their numbers (i.e. at puberty the uterus gets larger) |
| myoblasts | mesoderm cells that make muscle cells |
| Duchenne muscular dystrophy | most common and serious form, sex-linked recessive disease expressed in mostly males, results in respiratory death around 20s |
| RICE | acronym for rest, ice, compression, and elevation/ standard treatment for pulled muscle |
| strain | pulled muscle |
| spasm | involuntary muscle twitch, i.e. tic of the eye |
| myopathy | any disease of muscle |
| myalgia | muscle pain from any muscle disorder |
| cramp | sustained spasm or tetanic contraction of an entire muscle |
| Calcium channel blockers | drugs that interfere with the transport of Calcium across plasma membrane thus inhibiting muscle contraction, i.e. muscle relaxer |
