Study Guide for Exam 5 Including Cumulative Portion Lesson 20 What are the six functions of skeletal muscle tissue Six Functions of Skeletal Muscle Tissue o 1 Produce skeletal movement voluntary o 2 Maintain posture and body position o 3 Support soft tissues line the abdominal wall and pelvic cavity o 4 Guard entrances and exits ex Sphincters in alimentary canal urethra o 5 Maintain body temperature ex contractions produce heat shivering o 6 Store nutrient reserves breaks down muscle protein when needed How are skeletal muscles organized What are connective tissue layers that are found covering muscles What can be found in each layer blood vessels nerves Skeletal muscle organization includes o Muscle tissue muscle cells or fibers A muscle cell is also referred to as a muscle fiber o Associated with the tissue are Connective tissues nerves blood vessels Skeletal muscles have 3 layers of connective tissue o Epimysium o Perimysium o Endomysium Exterior collagen layer Connected to deep fascia Separates muscle from surrounding tissues Surrounds muscle fiber bundles form fascicles Contains blood vessel and nerve supply to fascicles Surrounds individual muscle cells muscle fibers Contain capillaries and nerve fibers contacting muscle cells Contain myosatellite cell stem cells that can repair some damage minimal repair ability What are the structural components of a muscle fiber What are myofibrils What are myofilaments Skeletal muscle cells Myofibrils o Develop through fusion of mesodermal cells myoblasts o Contain hundreds of nuclei o Become very large o Are very long o Lengthwise subdivisions WITHIN muscle fiber o Made up of bundles of protein filaments myofilaments o Myofilaments are responsible for muscle contraction o Types of myofilaments Thin filaments Made of the protein actin Thick filaments Made of the protein myosin What are the differences between thick and thin filaments How are they organized in muscle fibers How are they arranged in a sarcomere Thin filaments are made of the protein actin o F Actin filamentous actin two twisted rows of globular G actin The active sites on G actin strands bind to myosin o Tropomyosin double strand regulatory protein Prevents actin myosin interaction o Troponin a globular regulatory protein Binds tropomyosin to G actin Controlled by Ca2 binding of Ca2 causes a change in troponin Thick filaments are made of the protein myosin o Contain about 300 twisted myosin subunits o Contain titin strands that recoil after stretching Helps keep thick and thin filaments aligned and restores resting sarcomere length after contraction o The myosin molecule consists of Tail binds to other myosin molecules Head made of two globular protein subunits Can extend and bind to myosin binding site of the nearest thin filament Sarcomeres The contractile units of muscle o Strucutral units of myofibrils Form visible patterns within myofibrils A striped or striated pattern within myofibrils Alternating dark thick filaments A bands and light thin filaments I bands What are the zones and lines in a myofibril What are the different regulatory and structural proteins found in a muscle fiber What are their functions o Alternating dark thick filaments A bands and light thin filaments I bands The A Band M line the center of the A band o at midline of sarcomere The H band the area around the M line o Has thick filaments but no thin filaments Zone of Overlap the denset darkest area on a ligh micrograph o Where thick and thin filaments overlap The I Band Z lines the centers of the I bands o At two end of sarcomere Titin are strand of protein o Reach from tips of thick filaments to the Z line o Stabilize the filaments How are T tubules related to the sarcolemma Why are they important to a muscle fiber What is a triad and why is it important The sarcolemma and transverse tubules o The sarcolemma the cell membrane of a muscle fiber cell Surrounds the sarcoplasm cytoplasm of muscle fiber A change in transmembrane potential begins contractions o Transverse tubules T tubules invagination of the sarcolemma Have same properties as sarcolemma Transmit action potential through cell Allow entire muscle fiber to contract simultaneously The Sarcoplasmic Reticulum SR o Traid is formed by one T tubule and two terminal cisternae cisternae functions to concentrate Ca2 via ion pumps Ca2 pumps use ATP to actively pump Ca2 into the SR from the sarcoplasm when stimulated by an action potential the cisternae release Ca2 into sarcomeres to begin muscle contraction What is the function of calcium in muscle contraction Where is it normally concentrated in a muscle fiber How is it concentrated there Initiating Contraction o Ca2 binds to receptor on troponin molecule o Troponn tropomyson complex changes active site of the F Actin strand Exposes active site of actin Concentrated in the cisternae Tropomyosin strand shifts in position so it no longer covers the o Needs to be stimulated by an action potential to be released into sarcomeres Describe the sliding filament theory Sliding filaments and Muscle Contraction o Sliding filament theory Thin filaments of sarcomere slide toward M line alongside thick filaments The width of A band stays the same The width of the H band and I band shrinks during contraction Z lines move closer together Lesson 21 What are the steps to excitation contraction coupling starting from an action potential that reaches the axon terminal of a motor neuron and ending with the thick and thin filaments interacting with each other Which neurotransmitter is released by the motor neuron What effect does the neurotransmitter have on the muscle fiber How is the neurotransmitter s activity stopped at the neuromuscular junction Skeletal Muscle Contraction action potential that travels along the sarcolemma and down the T tubule cause release of Ca2 which allows for actin myosin interaction o The process of contraction Neural stimulation of sarcolemma Causes excitation contraction coupling o Action potential reaches a triad t tubule and terminal cisternae of the sarcoplasmic reticulum Releasing Ca2 from the terminal cisternae of the sarcoplasmic reticulum Triggering contraction IF They myosin heads are in primed high energy position o Used ATP energy to get into this position ATP hydrolyzed to ADP Pi on myosin head Muscle fiber contraction Caused by thick and thin filament interaction Tension production The neuromuscular junction NMJ o Special intercellular connection between the nervous
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