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KIN 3600
lec 19
| Question | Answer |
|---|---|
| Transverse Tubules (T-Tubules) | extensions of the cell membrane that penetrate into the centre of skeletal and cardiac muscle cells. |
| THERE ARE 2 TUBULES | EVERY 1 SARCOMERE |
| Cardiac muscle | 1 t-tubule |
| Skeletal muscle | 2 t-tubule |
| T-Tubules Average diameter | 0.04mm (40nm) |
| T-tubules network | @ every A-I band junction |
| Sarcoplasmic reticulum | specialized type of smooth ER that regulates the calcium ion concentration in the cytoplasm of striated muscle cells |
| The sliding filament theory | Thin pulls thick over center sarcomere which is pulling the z-disc along |
| What is doing the pulling for the thin myofibril? What is the molecular motor? | Head of myosin molecule |
| How are the thin filaments pulled over along thick filaments, what structures generate the force, there is the molecular motor? | Myosin head pulls with attached actin & brings the heads closer together |
| Cross Bridges | Form between thick and thin filaments Actin and myosin head attach |
| Length-tension relationship | Force developed by muscle depends on lengthn |
| Power stroke | Formation of strong bond (contracted muscle) with thin filament |
| Strong bond | o Release inorganic phosphate o Formation of weak bond |
| When muscle is relaxed | o Cross bridges are waiting & energized o Utilized before |
| Cross bridge recycling during muscular contraction | o Formation of weak bond o Re-energized cross bridges o Repeating the cycle |
| Cross bridges Duration of cycling | 50ms |
| Since skeletal muscle can shorten by 40% means | cross-bridges must recycle many times o Asynchronous cycling of cross bridges |
| Rigor Mortis (“death”): | muscle remains contracted and cannot resynthesize ATP for relaxation (locked state) |
| About 50% of all the cross-bridges | are in strong bond s |
| Both range & velocity of muscle shortening depends on | length (# of sarcomere) of muscle |
| The longer is the muscle fiber | greater its range & velocity of contractions |
| What determines force? | How many arranged side by side / How thick the muscle is |
| If myosin binding site on thin filament is exposed | the cross bridge will recycle continuously |
| Relaxation is caused by | deactivation of myosin binding sites on thin filament -Turn on and off contraction: o Role of troponin-tropomyosin complex |
| Excitation-Contraction coupling | Voltage-regulated Ca++ gates |
| Voltage-regulated Ca++ gates | -ATP -Calcium rushes out (100,000 fold different in Ca concentration) -Troponin C binds calcium -Something else -Unblock myosin binding sites -Pumping Ca++ back into the SR |
Created by:
rmart11
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