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muscles structure
| Question | Answer |
|---|---|
| What are the structural components of skeletal muscle fibres | Skeletal muscle fibres are long, cylindrical, multi-nucleated, and striated. They contain myofibrils, which are composed of repeating units called sarcomeres. |
| What are sarcomeres, and why are they important | Sarcomeres are the basic units of muscle contraction, made up of thick (myosin) and thin (actin) filaments that interact to produce muscle contraction. |
| Describe the role of calcium in skeletal muscle contraction | Calcium is released from the sarcoplasmic reticulum in response to an action potential. It binds to troponin, allowing myosin heads to bind to actin and initiate the cross-bridge cycle, generating contraction. |
| What are the primary energy sources for muscle contraction | ATP, phosphocreatine (PCr), anaerobic glycolysis, and oxidative phosphorylation. |
| What are the characteristics and roles of Type I (slow-twitch) muscle fibres | highly aerobic, resistant to fatigue, and suited for endurance activities due to their oxidative capacity. |
| Describe the function of Type IIa (fast-twitch oxidative) fibres. | aerobic and fatigue-resistant but are also capable of moderate-intensity activities and are suitable for repetitive actions like running or cycling. |
| What are Type IIx fibres, and when are they used? | fast-twitch glycolytic fibres, highly anaerobic, and produce powerful, quick contractions for short bursts of activity, such as sprinting or jumping. |
| What role does creatine kinase play in muscle contraction? | Creatine kinase helps regenerate ATP from phosphocreatine, supporting high-intensity muscle contraction. |
| What initiates the cross-bridge cycle in skeletal muscle contraction? | Calcium binds to troponin, causing a conformational change that allows myosin heads to bind to actin filaments. |
| How does the regulation of calcium differ between skeletal and smooth muscle? | In skeletal muscle, calcium binds to troponin to initiate contraction, while in smooth muscle, calcium binds to calmodulin. |
| Describe the function of anaerobic glycolysis in muscle energy production. | Anaerobic glycolysis provides quick energy without oxygen, yielding 2 ATP per glucose and producing lactate, which supports high-intensity activity. |
| What is the primary energy source for prolonged muscle activity, and how does it work? | Oxidative phosphorylation, which uses oxygen to produce approximately 32 ATP per glucose, supporting sustained, moderate-intensity exercise. |
| What happens to lactate levels during high-intensity exercise? | Lactate levels increase due to anaerobic glycolysis, indicating a shift to anaerobic metabolism as oxygen becomes limited. |
| What is the difference between single-unit and multi-unit smooth muscle? | Single-unit smooth Muscle: This muscle has fibres that contract as a unit and is found in organs like the GI tract, bladder, and uterus. Multi-Unit Smooth Muscle: Fibers function independently, allowing precise control, as in the iris and ciliary muscles. |
| How is contraction regulated in smooth muscle compared to skeletal muscle? | In smooth muscle, calcium binds to calmodulin, activating myosin and initiating contraction, whereas skeletal muscle contraction is regulated by calcium binding to troponin. |
| What structural features are unique to cardiac muscle? | Cardiac muscle has striated fibres with branching, intercalated discs containing gap junctions and desmosomes, enabling synchronised contraction. |
| Explain the role of calcium-induced calcium release (CICR) in cardiac muscle. | CICR is a mechanism where calcium influx triggers additional calcium release from the sarcoplasmic reticulum, essential for sustained cardiac muscle contraction. |
| How does the SA node influence heart rhythm in cardiac muscle? | The SA node generates pacemaker potentials, setting the rhythm for heartbeats and initiating electrical impulses that spread through the heart. |
| What energy source primarily supports cardiac muscle contraction? | Cardiac muscle relies on aerobic metabolism through oxidative phosphorylation, producing ATP for continuous, rhythmic contractions. |
| Compare the calcium regulation in skeletal, smooth, and cardiac muscle. | Skeletal Muscle: Calcium binds to troponin. Smooth Muscle: Calcium binds to calmodulin. Cardiac Muscle: Calcium influx triggers additional release from the sarcoplasmic reticulum (CICR). |
| Which muscle type is best suited for endurance activities and why? | Slow-twitch (Type I) muscle fibres in skeletal muscle are best suited for endurance due to their high oxidative capacity and resistance to fatigue. |
| What role do intercalated discs play in cardiac muscle function? | Intercalated discs facilitate electrical coupling and synchronisation of heart muscle contractions, essential for a coordinated heartbeat. |
| How does the energy production differ in high-intensity vs. moderate-intensity exercise? | High-intensity exercise relies on anaerobic glycolysis for quick energy, producing lactate, while moderate-intensity exercise depends on oxidative phosphorylation for efficient, sustained ATP production. |
Created by:
REDZ17
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