Term
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Definition
densely packed rodlick elements
make up 80 percent of cell volume
exhibit striations: perfectly aligned repeating series of dark a bands and light i bands |
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Term
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Definition
smallest contractile unit of a muscle fiber
the region of a myofibril between two successive z disks
composed of thick and thin myofilaments composed of contractile proteins |
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Term
| features of a sarcomere: thick filaments |
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Definition
| run the entire length of an A band |
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Term
| functions of a sarcomere: thin filaments |
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Definition
| run the length of the i band and partway into the a band |
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Term
| features of a sarcomere: z disk |
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Definition
| proteins that anchor thin filaments |
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Term
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Definition
| lighter midregion where filaments do not overlap |
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Term
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Definition
| protein that hold adjacent thick filaments together |
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Term
| ultrastructure of thick filaments |
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Definition
composed of the protein myosin
- myosin tails
- myosin heads
are atpase enzymes |
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Term
| ultrastructure of thin filaments |
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Definition
twisted strand of the protein actin
bears active sites for myosin head attachment during contraction |
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Term
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Definition
stores ca2
network of SER surrounding each myofibril |
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Term
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Definition
continuous with the sarcolemma
penetrates cell's interior at each A band-I band junction
- t tubules conduct impulses deep into muscle fiber |
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Term
| Events at the Neuromuscular Junction -Axons of motor neurons: |
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Definition
| travel from the central nervous system via nerves to skeletal muscles |
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Term
| Events at the Neuromuscular Junction - Each axon: |
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Definition
| forms several branches as it enters a muscle |
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Term
| Events at the Neuromuscular Junction - Each axon ending forms: |
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Definition
| a neuromuscular junction with a single muscle fiber |
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Term
| Events at the Neuromuscular Junction - Axon terminal and muscle fiber are: |
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Definition
| separated by the synaptic cleft |
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Term
| Events at the Neuromuscular Junction Synaptic vesicles of axon terminal contain: |
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Definition
| the neurotransmitter acetylcholine |
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Term
| Events at the Neuromuscular Junction - Junctional folds of the sarcolemma contain: |
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Definition
| Ach receptors (motor end plate) |
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Term
| Events at the Neuromuscular Junction - A nerve impulse: |
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Definition
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Term
| Events at the Neuromuscular Junction - Ach is: |
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Definition
| released an it binds with the receptors on the sarcolemma |
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Term
| Nerve stimulus and action potential: |
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Definition
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Term
| Role of calcium in contraction - low intracellular calcium concentration: |
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Definition
Active sites on actin are blocked
Myosin heads cannot attach to actin
muscle fiber relaxes |
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Term
| Role of calcium in contraction - high intracellular calcium concentration |
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Definition
Calcium causes binding sites on actin to be exposed
Events of the cross bridge cycle occur
When nervous stimulation ceases calcium is pumped back into the sarcoplasmic reticulum and contraction ends |
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Term
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Definition
Continues as long as the calcium signal and adequate atp are present
Cross bridge formation: myosin head attaches to thin filament
Working (POWER) stroke myosin head pivots and pulls thin filaments toward the M line
Cross bridge detachment - atp attaches to myosin head and the cross bridge detaches
"cocking of the myosin head": energy from hydrolysis of atp cocks the myosin head into the high energy state |
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