BSC 2085 Final Exam 5 Study Guide Lesson 20 The Muscular System I Describe the three types of muscle tissue a Skeletal muscle tissue voluntary control b Cardiac muscle tissue located in the heart involuntary control c Smooth muscle tissue located in viscera blood vessels involuntary control II Explain the function of skeletal muscle tissue a 6 functions of skeletal muscle tissue i Produce skeletal movement voluntary control ii Maintain posture and body position Support soft tissues line abdominal wall and pelvic cavity Guard entrances and exits sphincters in alimentary canal v Maintain body temperature contractions aka shivering produce heat vi Store nutrient reserves muscle protein breaks down when nutrients needed iii iv ii iii iv b Components of skeletal muscle i Muscle tissue muscle cells or fibers Connective tissues Nerves Blood vessels a Organization of tissues i Epimysium 1 Exterior collagen layer 2 Connected to deep fascia III Describe the connective tissue that covers skeletal muscles 3 Separates muscle from surrounding tissues ii Perimysium 1 Surrounds muscle fiber bundles fascicles 2 Contains blood vessel and nerve supply to fascicles iii Endomysium 1 Surrounds individual muscle cells muscle fibers 2 Contains capillaries and nerve fibers contacting muscle cells 3 Contains myosatellite cells stem cells that repair damage b How do they form tendons aponeuroses 1 Muscle attachments a Endomysium perimysium and epimysium come together at ends of muscles to form connective tissue attachment to bone matrix i e tendon bundle or aponeurosis sheet IV Describe the characteristics of skeletal muscle cells Develop through fusion of mesodermal cells myoblasts a Characteristics i ii iii Become very large Contain hundreds of nuclei iv Are very long b What are the function of the sarcoplasmic reticulum and transverse tubule 1 Caused when myoblasts fuse together each nucleus originates from a single myoblast i Sarcolemma the cell membrane of a muscle fiber cell 1 Surrounds the sarcoplasm cytoplasm of muscle fiber 2 A change in transmembrane potential begins contractions ii Transverse tubules T tubules 1 Transmit action potential through cell 2 Allow entire muscle fiber to contract simultaneously 3 Have same properties as sarcolemma c Myofibrils i Lengthwise subdivisions within muscle fiber ii Made up of bundles of protein filaments myofilaments iii Myofilaments are responsible for muscle contraction iv Types of myofilaments 1 Thin filaments made of actin 2 Thick filaments made of myosin d The Sarcoplasmic Reticulum i ii iii iv A membranous structure surrounding each myofibril Similar in structure to smooth ER Forms chambers terminal cisternae attached to T tubules Helps transmit action potential to myofibril a M line center of the A band at midline of sarcomere b H band are around the M line has thick filaments but NO thin filaments c Zone of Overlap the densest darkest area on a light micrograph where thick and thin filaments overlap 2 Light thin filaments I bands a Z lines the centers of the I bands at two ends of sarcomere b Titin strands of protein reach from tips of thick filaments to the Z line stabilize the filaments v Triad 1 Formed by one T tubule and two terminal cisternae V Describe the arrangement of the sarcomere a Sarcomere contractile units of muscle i ii iii Structural units of myofibrils Form visible patterns within myofibrils A striped or striated pattern within myofibrils VI Explain how the myofilaments are arranged in the sarcomere a A striped or striated pattern within myofibrils 1 Alternating dark thick filaments a bands VII Describe the components of the thin and thick filaments a Thin filaments i F actin filamentous actin 1 Two twisted rows of globular G actin 2 The active sites on G actin strands bind to myosin ii Nebulin iii Tropomyosin iv Troponin b Thick filaments 1 Holds F actin strands together 1 Is a double strand that prevents actin myosin interaction 1 A globular protein that binds tropomyosin to G actin i ii iii Contain about 300 twisted myosin subunits Contain titin strands that recoil after stretching The myosin molecule consists of a Reaches the nearest thin filament can extend and bind to myosin binding site of the nearest thin 1 Tail binds to other myosin molecules 2 Head made of two globular protein subunits filament VIII Explain how the thick and thin filaments interact a Myosin action i During contraction myosin heads 1 Interact with actin filaments forming cross bridges 2 Povot producing motion b What is the sliding filament theory i ii iii Thin filaments of sarcomere slide toward the M line alongside thick filaments The width of A zone band stays the same Z lines move closer together sarcomere length shortens IX Describe the neuromuscular junction and excitation contraction coupling a Process of contraction a Neural stimulation of sarcolemma causes excitation contraction coupling b Muscle fiber contraction i Interaction of thick and thin filaments c Tension produced b Control of skeletal muscle activity a Neuromuscular junction NMJ i Special intercellular connection between the nervous system and skeletal muscle fiber ii Neurotransmitter ACh Acetylcholine released into synaptic cleft causes action potential in muscle fiber iii Muscle fiber responds by releasing calcium ion into the sarcoplasm Lesson 21 The Muscular System Muscle Contraction I Describe the events that occur at the neuromuscular junction during the generation of an action potential at the sarcolemma II Describe the steps to excitation contraction coupling a The cytoplasm of the axon terminal contains vesicles filled with molecules of acetylcholine or ACh Acetylcholine is a neurotransmitter a chemical released by a neuron to change the permeability or other properties of another cell s plasma membrane The synaptic cleft and the motor end plate contain molecules of the enzyme acetylcholinesterase AChE which breaks down ACh b The stimulus for ACh release is the arrival of an electrical impulse or action potential at the axon terminal An action potential is a sudden change in the membrane potential that travels along the length of the axon c When the action potential reaches the neuron s axon terminal permeability changes in its membrane trigger the exocytosis of ACh into the synaptic cleft Exocytosis occurs as vesicles fuse with the neuron s plasma membrane d ACh molecules diffuse across the synaptic clef and bind to ACh receptors on the surface of the motor end plate ACh binding
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