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21 Cards in this Set
- Front
- Back
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What are the 3 Muscle types? |
Cardiac Smooth Skeletal |
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What provides the energy for muscle contraction? |
Hydrolysis of ATP
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What is the hierarchical structure of skeletal muscle? |
Muscle- Fascucli (Bundles) - Miscle Fibres (cell)- Myofibrils - Myofilament proteins (Actin and myosin) |
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Give some features of skeletal muscle? |
Long cylindrical cell Multiple peripheral nuclei Sarcolemma- Plasma Membrane Sacroplasm - Cytoplasm Sarcoplasmic reticulum - Intracellular Ca2+ stores, T-tubules (regulation of muscle contraction) |
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Why is skeletal muscle striated? |
The repeating series of dark A (myosin) and I (actin) bands. |
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What is the Z line of the sarcomere? |
The central line in the middle of the Actin (I band) |
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What is the M line of the sarcomere? |
The central line in the middle of the Myosin (A band) |
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What is the H zone? |
The area of Myosin which doesn't overlap with actin. |
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What happens to the Z lines during muscle contraction? |
They get closer together |
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Describe the structure of the myosin filament. |
2 Heavy chains and 4 Light chains Consists of helical tail and globular head Head consists of ATP binding site and has ATPase activity. Each thick filament contains myosin molecules bundled with heads projecting out and exposed to actin filaments. |
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Describe the structure of the Actin Filament. |
Globular subunits bear active sites for myosin head attachment Associated with tropomyosin (stabilises actin) In abscence of Ca2+ tropomyosin binding site on actin. Troponin: 3 polypeptide complex (Tn-C, Tn-I, Tn-CT) C= calcium binding, I= inhibitory subunit, T= tropomyosin binding. |
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What happens during cross bridge formation? |
Calcium binds to Tn-C Induces Changes in Tn-I which are transduced through Tn-t to tropomyosin Exposing the binding site, permitting cross bridge formation |
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Describe the 4 stages of muscle contraction |
1. Cross bridge formation 2. The power stroke- ADP and Pi are released and the myosin head pivots and bends, changing to its bent low energy state and pulling actin filament towards M line 3. Cross bridge detachment- After ATP attaches to myosin, the link between myosin and actin weakens and the myosin head detaches 4. Cocking of the myosin head- An ATP is hydrolysed to ADP and Pi the myosin head returns to its pre-stroke high-energy or cocked position |
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What is excitation-contraction coupling? |
The sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments. |
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Give the 4 steps of E-C (excitation contraction) coupling. |
1. AP propagates along the sarcolemma and down the T-tubules. 2. The transmission of AP down the T tubules of the triads cause voltage sensitive T tubules to change shape opening the Ca channels allowing Ca to flow into the cytosol. 3. Calcium binds to troponin and stops the blocking action of tropomyosin 4. Contraction begins. |
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What are ryanodine receptors? |
Calcium channels Located in sarcoplasmic reticulum Sensitive to depolarisation of the T tubules |
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What are the 3 sources of ATP for muscle contraction? |
Creatine phosphate Anaerobic glucose metabolism Aerobic respiration |
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How is creatine phosphate used to make ATP? |
When combined with ADP, creatine phosphate donates its phosphate to form ATP. |
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What is creatine phosphate synthesised from? |
Arginine, glycine and phosphorylated by creatine kinase |
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What are the two types of muscle fibre? |
Slow oxidative fibre: Slow contraction, generate ATP by aerobic mechanisms Fast glycolytic fibres: Fast contraction, generate ATP by anaerobic mechanisms |
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How can levels of each muscle fibre be modified? |
By exercising |
