BIO 240 1st Edition Lecture 17 Outline of Last Lecture I. Muscle TissueA. General characteristicsB. Functions C. Cell typesD. Specific characteristicsOutline of Current LectureII. Anatomy of Skeletal Muscle Fibers A. StructuresB. Skeletal Muscle FiberC. Anatomy of a MyofibrilCurrent Lecture1. Skeletal musclei. 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 muscleii. Perimysium Dense fibrous connective tissue thatcovers fascicles. iii. Endomysium Areolar connective tissue that wraps around and covers the myocytes. c. Functions of the connective tissue sheets:i. Prevent muscle overstretchingii. Helps muscle return to shapeiii. Provide a framework for blood vessels and nerves to grow to the muscle cellsii. Voluntaryiii. Multi-nucleatediv. Striated II. Anatomy of Skeletal Muscle Fibers A. Structures1.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 CellPlasma membrane SarcolemmaCytoplasm SarcoplasmCytoskeleton & Cell organelles Myofibrils & Myofilaments *two unique muscle cell organelles. i. Sarcolemma The plasma membrane of a muscle fiberii. Sarcoplasm The cytoplasm of a muscle fiberiii. Myofibril Contains proteins (myofilaments) responsible for contraction. iv. Myofilaments Thick filaments- myosin, and thin filaments- actin. v. Sarcomere The functional, contractile unit of skeletal muscle. Occurs from Z-line to Z-line. B. Skeletal Muscle Fiber 1. Muscle fiber Muscle cell2. Myofibril Smaller tubes that the muscle fiber is made up of3. Filaments Thick and thin; make up the myofibrilsC. Anatomy of a myofibril*** During muscle relaxation1. 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
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