Bio 2 Notes Chapter 38
Bio 2 Notes Chapter 38 BIOL 1040
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This 2 page Class Notes was uploaded by Courtney Luber on Saturday February 13, 2016. The Class Notes belongs to BIOL 1040 at Clemson University taught by Dr. William Surver in Fall 2016. Since its upload, it has received 21 views. For similar materials see General Biology II in Biology at Clemson University.
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Date Created: 02/13/16
Chapter 38: Musculoskeletal System Muscle Tissue—most abundant tissue in animals o Smooth—not striated; involuntary o Skeletal—striated; voluntary o Cardiac—striated; involuntary Muscles & bones interact to produce movement o Antagonistic Muscles are connected to bones by tendons o Can only contract requiring an antagonisticmuscle to Reverse the action Relengthen muscles Muscle fiber = muscle cell Skeletal muscle o Multinucleated o Striated Sarcomere—the functional unit of skeletal muscle what contracts and relaxes and allows the muscle to function o Unit of contraction in skeletal muscle o Z bands = dark bands on end of sarcomere Actin—thin fibers; attached to z lines Myosin—thick fibers; between actin; not attached to anything Muscle cell shortens because the sarcomere within it is shortening Know anatomy of sarcomere & how it functions Skeletal Muscle Contraction o Sliding filament model—a sarcomere contracts (shortens) when its thin filaments slide across thick filaments; mechanism by which the sarcomere shortens Contraction shortens the sarcomere without changing the lengths of the thick and thin filaments Actin slides across myosin—myosin stays put; myosin reaches and grabs hold of actin When a muscle is fully contracted, the thin filaments overlap in the middle of the sarcomere I band = area near z-line H zone = all myosin; disappears when sarcomere contracts o Myosin heads of the thick filaments Bind to ATP and Extend to high energy states o Myosin heads then Attach to binding sites on the actin molecules Pull the thin filaments toward the center of the sarcomere o A motor neuron Carries an action potential to a muscle cell Releases the neurotransmitter acetylcholine from its synaptic terminal and initiates a muscle contraction An action potential in a muscle cell passes along the T tubules and into the center of the muscle fiber o Calcium ions Without calcium being released, a muscle would never contract Calcium releases myosin-binding sites Are released from the ER Bind to the regulatory protein tropin resulting in the movement of tropomyosin away from the myosin-binding sites and allowing contraction to occur o When motor neurons stop sending action potentials to the muscle fibers The ER pumps Ca++ back into the cytosol Binding sites on the actin molecules are again blocked The sarcomeres stop contracting The muscle relaxes o Neuromuscular junction—where neuron and muscle connect
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