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What is the thick filament composed of?
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About 300 myosin protein molecules
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Describe the myosin molecules.
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Has two basic regions. A tail like region and two myosin heads. Looks like a two headed golf clubs.
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What appears on the myosin head of the thick filament and what is its function?
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ATPase (enzyme) This is the enzyme needed to catalize the hydrolisis ATP to ADP. Each head also has an actin binding site to the thin filament.
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How many proteins are in the thin filament? Describe each and where they are.
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Three. Actin (beanlike protein that has myocin binding site). Lying over the myosin binding sites are two regulartary proteins. (Tropomyosin lays across binding site and Troponin lies over the tropomyosin holding it in place.) Troponin has a region that can bind to calcium.
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Where is the calcium located when the myosin binding sites are covered up?
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Located in the SR when the muscle is at rest. Ready once binding site is uncovered.
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What are the thick filaments made of?
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Myosin protein
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What are the thin filaments made of?
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Actin
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What covers the myosin binding sites on the actin?
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Tropomyosin and troponin
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What is the job of the tropomyosin?
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It covers the actin binding site
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What is the job of the troponin?
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It holds the tropomyosin in place.
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Describe the structure of the muscle cell (from larger working in to smallest)
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As the muscle cell structure get smaller, the name gets longer. Largest is the muscle fiber/myofiber (the whole muscle cell), then myofibrals (100's -1000's inside of muscle cell), then myfilaments (inside of each myofibrals.
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What controls a muslce cell?
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Each muscle cell has its very own nerve cell that controls it.
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Explain steps of muscle contraction:
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1. Every muscle cell is controlled by a single motor newron
2. Muscle cells are excitable and will start an action potential 3. The action potential releases a chemical called ACh from the somatic motor neuron. 4. ACh diffuses across the synaptic cleft (space) and bind with ACh receptors on muscle membrane. (sarcolemma) and is called the motor endplate. This opens up the sodium channels which leads to an action potential. 5. AP travels along the sarcolemma and travels down the t-tubules and opens the Calcium gates in the SR. 6. Calcium can now rush out into sarcoplasm. Binds to troponin. This opens the myosin binding sites. |
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What does "excitable" mean in regards to a muscle cell?
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It will generate a special electric surrent when properly stimulated. This special electric current called action potential.
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What is the stimulus needed to generate the special electic current in a muscle?
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A chemical called acetylcholine (ACh)
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