<p>Muscle Cell Function Vertebrate Anatomy – Ch. 9 </p><p>Muscle cell structure</p><p> Long, cylindrical cell Produced by union of many ______cells; Leads to huge cells - Up to 12 inches long; 10x larger in diameter than avg. cell Many ______in each fiber; Again, indicates fusion of many cells</p><p>- Arranged just below the plasma membrane - Nuclei pushed to periphery to make more room for unified contracting fibers Plasma membrane – called ______ Cytoplasm – called ______ Muscle cells contain Lots of stored ______- a sugar storage molecule that can provide lots of ______ Muscle cells also contain lots of ______which is an ______- binding protein. Lots of oxygen is needed for energy production. This molecule is a lot like ______which carries oxygen in the ______.</p><p>Muscle fiber - close up</p><p>Each muscle fiber contains a large number of rod-like ______that run in parallel fashion and extend the entire length of the cell.</p><p>Myofibrils are densely packed within the muscle fiber.</p><p>Myofibrils appear ______. These bands are also called ______- Hence, the term striated muscle is used to describe skeletal muscle.</p><p>Banding is due to two types of smaller fibers</p><p>______filaments - made of ______</p><p>______filaments – made of ______</p><p>Thick filament structure</p><p>Myosin is long filaments that have small "knobs" hanging off called myosin ______.</p><p>Myosin heads can ______and “stick to” ______at certain locations on the actin fiber</p><p>Thin filament structure</p><p>Actin - ______strings of ______</p><p>Actin molecules possess ______sites. These are locations where</p><p>______heads can bind to the actin molecules These myosin head binding sites remain ______when the muscle is NOT contracting</p><p>Troponin and Tropomyosin</p><p>Troponin and Troposmyosin are molecules associated with the ______filaments</p><p>Troponin Troponin molecules are actually ______binding sites also located on actin filaments</p><p>Tropomyosin “rope” molecule that covers and hides ______binding sites</p><p>The Sarcomere</p><p>The ______is the unit of muscle contraction</p><p>______– anchor points for actin filaments</p><p>Sarcomere – extends from from ______to ______</p><p>Interaction of Thick and Thin filaments – muscle contraction</p><p>1. Myosin head bound to ______.</p><p>At this point, myosin head is in a ______energy state</p><p>Energy from ATP cannot be released until ATP is broken into ______and ______</p><p>2. Myosin head hydrolyzes (breaks down) ATP to ADP and Pi.</p><p>Release of energy causes myosin head to change its shape. It moves to its ______energy position.</p><p>3. Myosin head binds to ______forming a ______</p><p>This occurs as long as the myosin ______sites on the actin filaments have been </p><p>______. Remember these were hiddin by the ______molecule</p><p>4. Once the myosin head binds to actin, it releases ADP and Pi Once ADP and Pi are released, myosin head returns to Low Energy State</p><p>REMEMBER: The myosin head is still hooked to the ______molecule! THIS ______THE THIN FILAMENT</p><p>5. A new ______binds to the ______. This causes a shape change in the myosin head that releases the myosin head from the actin molecule But that’s not all….</p><p>Remember Tropomyosin, Troponin and Calcium ….. Where do these chemicals fit it in? They help to </p><p>______of the muscle contraction – that is, they help determine WHEN the </p><p> muscle will contract. This is based on a signal sent from your BRAIN (usually).</p><p>Control of muscle contraction:</p><p>Tropomyosin covers ______binding sites on actin filaments</p><p>Troponin – these molecules are ______binding sites</p><p>Here's how it works:</p><p>1. Calcium binds to ______.</p><p>2. When bound by calcium, Troponin molecules ______– this causes </p><p>______molecules to move, too.</p><p>When tropomyosin molecules move, the ______binding sites are revealed.</p><p>This allows the myosin head to bind to the actin filament, forming a crossbridge.</p><p>BUT…where does this calcium come from and WHY?</p><p>Calcium is stored in the ______(fancy ER)</p><p>A ______is responsible for releasing calcium from SR into </p><p>______(cytoplasm).</p><p>1. Nerve impulse travels across from neuron (nerve cell) across a synapse to the </p><p>______(muscle cell membrane).</p><p>2. The nerve impulse follows the sarcolemma until it "falls down the manhole" – that is, </p><p> until it falls down the ______. These are tubes of cell </p><p> membrane that carry the impulse down into the cell.</p><p>3. Impulse travels to the ______</p><p>4. When nerve impulse reaches SR, ______is released</p><p>This ensures that muscle contraction occurs, ONLY when the nerve impulse has told it to do so. </p>
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