BIO 240 1st Edition Lecture 17 Outline of Last Lecture I Muscle Tissue A General characteristics B Functions C Cell types D Specific characteristics Outline of Current Lecture II Anatomy of Skeletal Muscle Fibers A Structures B Skeletal Muscle Fiber C Anatomy of a Myofibril Current Lecture 1 Skeletal muscle i Associated connective tissues a Tendons Attaches muscle to bone b Connective tissue sheets Sheaths of connective tissue that cover all skeletal muscle There are 3 types i Epimysium Dense irregular connective tissue that wraps around the entire muscle ii Perimysium Dense fibrous connective tissue that covers fascicles iii Endomysium Areolar connective tissue that wraps around and covers the myocytes c Functions of the connective tissue sheets i Prevent muscle overstretching ii Helps muscle return to shape iii Provide a framework for blood vessels and nerves to grow to the muscle cells ii Voluntary iii Multi nucleated iv Striated II Anatomy of Skeletal Muscle Fibers A Structures 1 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Typical Cell Muscle Cell Plasma membrane Sarcolemma Cytoplasm Sarcoplasm Cytoskeleton Cell organelles Myofibrils Myofilaments two unique muscle cell organelles i Sarcolemma The plasma membrane of a muscle fiber ii Sarcoplasm The cytoplasm of a muscle fiber iii Myofibril Contains proteins myofilaments responsible for contraction iv Myofilaments Thick filaments myosin and thin filamentsactin v Sarcomere The functional contractile unit of skeletal muscle Occurs from Z line to Z line B Skeletal Muscle Fiber 1 Muscle fiber Muscle cell 2 Myofibril Smaller tubes that the muscle fiber is made up of 3 Filaments Thick and thin make up the myofibrils C Anatomy of a myofibril During muscle relaxation 1 M line Structure that runs down the middle of the myosin filaments anchoring them in place 2 Z line Zigzag line that runs down the middle of the actin filaments anchoring them in place Also establishes the boarder of the sarcomeres 3 A band Dark band mostly made of thick filaments with the ends of thin filaments overlapping i H zone The middle of the thick filaments where no thin filaments overlap during relaxation 4 I band Light band the middle of the thin filaments with no overlapping thick filaments During contraction the I band and H zone disappear
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