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Unit 5: Muscular System Lauren Palla, Period 6 - Coggle Diagram
Unit 5: Muscular System Lauren Palla, Period 6
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Neuromuscular Junction
Axon (thread of motor neurons) branches end at the muscle fiber, forming the neuromuscular junction.
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Sliding Filament Theory
The sliding filament theory explain s muscle contraction based on how muscle fibers (actin and myosin) slide against each other to generate tension in overall muscle.
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Step 5: ADP and P are released from myosin, which causes the myosin to move. This movement is called the power stroke.
Step 3: The calcium binds to the troponin located in the actin filament, causing the tropomyosin to move and expose the binding sites for myosin.
Step 6: ATP binds to myosin causing it to release the actin and reverting the ATP into ADP and P. The myosin is now ready to form another crossbridge and the cycle of contraction will continue until the impulse stops.
Step 2: The impulse travels down the membrane and into the T-Tubules were it causes calcium to be released into the sarcoplasmic reticulum.
Step 7: Once the impulse stops, calcium is released from troponin causing the tropomyosin to cover the binding sites and prevent contraction. Calcium returnms to the SR and waits for another impulse (relaxation).
Step 1: The brain/spinal cord sends an impulse to the muscle. This impulse then travels down the motor neuron and reaches a neuromuscular junction where it releases acetylcholine, which triggers the impulse in the muscle.
Disorders
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Duchenne Muscular Dystrophy (DMD)- most common and most serious form of muscular dystrophies (muscle-destroying diseases that generally appear during childhood).
Disease progresses from extremities upwards, finally affecting head, chest muscles, and cardiac muscles.
Caused by a defective gene for dystrophin, a protein that links thin filaments to extracellular matrix and helps stabilize sarcolemma.
Sarcolemma of DMD patients tear easily, allowing entry of excess calcium which damages contractile fibers.
Inflammation follows and regenerative capacity is lost, resulting in increased apoptosis of muscle cells; causes decrease in muscle mass.
Myasthenia Gravis- a disease characterized by drooping upper lids, difficulty swallowing or talking, or generalized muscle weakness
Involves shortage of ACh receptors due to the person's ACh receptors being attacked by own antibodies.
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Muscle Coverings
Muscle cover, or connective tissue sheaths, support the cells and reinforce the entire muscle.
Perimysium- fibrous connective tissue surrounding the fascicles, which are discrete bundles of muscle cells.
Endomysium- fine areolar connective tissue surrounding each muscle fiber, which are elongated mulitnucleate cells.
Epimysium- dense irregular connective tissue surrounding the entire muscle, which consists of hundreds of muscle cells, blood vessels, and nerve fibers.
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Types of Muscles
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Smooth Muscle- found in walls of hallow visceral organs, airways, and large arteries.
Function: aids in moving food along our digestive system and maintaining blood circulation through the blood vessels.
Characteristics: spindle-shaped, uninucleate, has no striations
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