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ebacker
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Who were the 2 most influential scientists of muscle physiology?
- Luigi Galvani
- Alessandro Volta
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What are the 3 classifications of muscles?
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What is a muscle?
Group of fascicles
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What are muscles fixed to?
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What is muscle membrane called?
Sarcolemma
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What is muscle cell plasm called?
Sarcoplasm
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What is the reticulum in muscle called and what is it similar to?
- Sarcoplasmic reticulum
- Smooth endoplasmic reticulum
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What gives muscles a striated appearance?
Myofibrils: actin and myosin
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What is thick filament?
Actin
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What is thin filament?
Myosin
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What is the smallest functional unit of muscle?
Sarcomeres
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- 1. A band
- 2. I band
- 3. H band
- 4. Crossbridges
- 5. Actin
- 6. Myosin
- 7. Z line
- 8. M line
- 9. Sarcomere
- 10. Myofibril
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- 1. Sarcomere
- 2. Z line
- 3. M line
- 4. H band
- 5. A band
- 6. I band
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What is a contractile protein?
Actin
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What are 2 regulatory proteins?
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What are the 3 types of troponin and what do they do?
- A - Actin binding
- T - Tropomyosin binding
- C - Calcium binding
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What are the 2 binding sites on actin heads?
- Actin-binding site
- ATPase site
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What is the "bare zone"?
Site on thick filament that has no crossbridges (heads)
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Which line/band are myosin head and tail near?
- Tail - toward M line
- Head - toward I band
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What provides elasticity in muscles?
Titin
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What is the sliding-filament model?
Thick and thin filaments do not shorten, they overlap and slide past e/o
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What bands shorten during contraction?
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What are crossbridge cycles?
Cyclical formation of links btwn actin and myosin resulting in the sliding of thin filaments toward the M ling of a sarcomere
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Crossbridge cycle
What is the power stroke?
Myosin head pivots, pulling the actin filament with it
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Crossbridge Cycle
What is rigor?
Myosin and actin are tightly bound
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Crossbridge Cycle
What is binding?
Pi is realeased from the ATPase site
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Crossbridge Cycle
What is cocking?
ATP is hydrolyzed; myosin is in its high-energy form
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Crossbridge Cycle
What is unbinding?
The myosin head detaches from the actin
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What is asynchronous cycling and why does it occur?
- Crossbridge cycles are purposely out of step with e/o
- Muscle cells can continuously generate force during contraction
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What is excitation-contraction coupling?
Sequence of events whereby an AP in the sarcolemma causes contraction
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What are the 2 most important factors in muscle contraction?
- Neural input from motor neuron
- Ca2+ release from sarcoplasmic reticulum
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What is the role of Ca2+ in contraction?
Binds to troponin = movement of troponin = movement of tropomyosin = exposed binding sites for myosin on actin = crossbridge cycle = contraction
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What are the 6 steps of excitation-contraction coupling?
- 1. AP in sarcolemma
- 2. AP down T tubules
- 3. DHP receptors of T tubules open Ca2+ channels in lateral sacs of SR
- 4. Ca2+ increases cytosol
- 5. Ca2+ binds to troponin, shifting tropomyosin
- 6. Crossbridge cycling occurs
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What are the 2 receptors involved in Ca2+ release?
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What must happen to terminate contraction?
- Ca2+ must leave troponin
- Tropomyosin covers myosin binding site on actin
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How is Ca2+ removed from cytosol?
Ca2+ ATPase in SR transports it from cytosol into SR
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