AN SC 310 - 13
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Who were the 2 most influential scientists of muscle physiology?
- Luigi Galvani
- Alessandro Volta
What are the 3 classifications of muscles?
What is a muscle?
Group of fascicles
What are muscles fixed to?
What is muscle membrane called?
What is muscle cell plasm called?
What is the reticulum in muscle called and what is it similar to?
- Sarcoplasmic reticulum
- Smooth endoplasmic reticulum
What gives muscles a striated appearance?
Myofibrils: actin and myosin
What is thick filament?
What is thin filament?
What is the smallest functional unit of muscle?
- 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
- 1. Sarcomere
- 2. Z line
- 3. M line
- 4. H band
- 5. A band
- 6. I band
What is a contractile protein?
What are 2 regulatory proteins?
What are the 3 types of troponin and what do they do?
- A - Actin binding
- T - Tropomyosin binding
- C - Calcium binding
What are the 2 binding sites on actin heads?
- Actin-binding site
- ATPase site
What is the "bare zone"?
Site on thick filament that has no crossbridges (heads)
Which line/band are myosin head and tail near?
- Tail - toward M line
- Head - toward I band
What provides elasticity in muscles?
What is the sliding-filament model?
Thick and thin filaments do not shorten, they overlap and slide past e/o
What bands shorten during contraction?
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
What is the power stroke?
Myosin head pivots, pulling the actin filament with it
What is rigor?
Myosin and actin are tightly bound
What is binding?
Pi is realeased from the ATPase site
What is cocking?
ATP is hydrolyzed; myosin is in its high-energy form
What is unbinding?
The myosin head detaches from the actin
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
What is excitation-contraction coupling?
Sequence of events whereby an AP in the sarcolemma causes contraction
What are the 2 most important factors in muscle contraction?
- Neural input from motor neuron
- Ca2+ release from sarcoplasmic reticulum
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
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
What are the 2 receptors involved in Ca2+ release?
What must happen to terminate contraction?
- Ca2+ must leave troponin
- Tropomyosin covers myosin binding site on actin
How is Ca2+ removed from cytosol?
Ca2+ ATPase in SR transports it from cytosol into SR
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