Learning Objectives Muscles

Learning Objectives Muscles - Learning Objectives for Dr...

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Learning Objectives for Dr. Barnett’s Lectures & Lab Skeletal Muscle Lecture 10: Skeletal Muscle: Muscle Structure -- Excitation-Contraction Coupling (see CT 4.1) 1. Draw and label a diagram that shows skeletal muscle at all anatomical levels. Illustrate the structural characteristics of whole muscle (intact muscles attached to the skeleton ), single muscle cells , myofibrils and sarcomeres ., At the sarcomere level your drawing should identify the molecular components that are the basis of its striated appearance. Include two different stages of myofilament overlap. (See CT 4.1) Skeletal muscle muscle fascicle muscle fibers sarcolemma (T-tubules) and sarcoplasm sarcoplasmic reticulum and myofibrils troponin, actin (thin filament), tropomyosin, myosin (thick filament), titin, and nebulin [all of which are organized into a sarcomere from z-disk to z-disk] 2. Draw the structure of the neuromuscular junction including important proteins that are found on the pre- and post-synaptic membranes (label these proteins and other structural features). (See CT 4.1) 3. List in sequence the steps involved in neuromuscular transmission in skeletal muscle and point out the location of each step on a diagram of the neuromuscular junction; name the neurotransmitter and explain the role and location of acetylcholinesterase . Acetylcholinesterase is located on the postsynaptic membrane and metabolizes acetylcholine in the synapse. Important because otherwise Na+ would continue to flow into cell causes continuous depolarization. Ca2+ ATPase on axon terminal to remove calcium from the synapse. 4. List the steps in excitation-contraction coupling in skeletal muscle, and describe the roles of the sarcolemma , transverse tubules , sarcoplasmic reticulum and the thin and thick filaments . Be certain to include the roles of modulatory proteins such as troponin and tropomyosin and of calcium ions. 1. Somatic motor neuron releases acetylcholine at neuromuscular junction 2. Net entry of Na+ through acetylcholine receptor-channel initiates a muscle action potential 3. Action potential in t-tubule alters conformation of DHP receptor 4. DHP receptor opens ryanodine receptor Ca2+ channels on sarcoplasmic reticulum and Ca2+ enters the cytoplasm 5. Calcium binds to troponin allowing actin-myosin binding 6. Myosin heads execute the power stroke 7. Actin filament slides toward center of sarcomere 8. Sarcoplasmic Ca2+/ATPase pumps calcium back into sarcoplasmic reticulum 9. Decrease in free cytosolic calcium causes calcium to unbind from troponin 10. Tropomyosin re-covers the binding site allowing myosin heads to release, elastic elements pull filaments back into their relaxed position 5. Diagram the chemical and mechanical steps in the cross-bridge cycle , and explain how the cross- bridge cycle results in shortening of the muscle.
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