NVC BIOL 105 - The Muscular System

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12/27/20091The Muscular SystemBiol 105Lecture 12Chapter 6Copyright © 2009 Pearson Education, Inc.OutlineI. Characteristics of musclesII. Three types of musclesIII. Functions of musclesIV. Structure of skeletal musclesV. Mechanics of muscle contractionVI. Energy source for muscle contractionCopyright © 2009 Pearson Education, Inc.Muscular System Remember there were different types of muscles: cardiac, smooth and skeletal.  All muscle cells are elongated and therefore are called muscle fibers. All muscle tissues contract. Muscles contain muscle cells (called muscle fibers), connective tissue, blood vessels, and nervesCopyright © 2009 Pearson Education, Inc.1. Smooth muscle2. Cardiac muscle 3. Skeletal muscle11-2Types of MusclesCopyright © 2009 Pearson Education, Inc. Smooth muscles are involuntary muscles found in the walls of many internal organs (digestive tract, respiratory system, blood vessels). Function to aid in the function of other organs11-2Smooth muscleCopyright © 2009 Pearson Education, Inc. Cardiac muscles are involuntary muscles found only in the heart wall. Functions by contracting to force blood from the heart into the arteries11-2Cardiac muscle12/27/20092Copyright © 2009 Pearson Education, Inc. Skeletal muscle are voluntary muscles attached to the skeleton.  Usually work in pairs11-2Skeletal muscle11-2Copyright © 2009 Pearson Education, Inc.Skeletal Muscles Work in Pairs Most skeletal muscles are antangonistic pairs. One muscle contracts, the other relaxes Muscles are attached to the bone by tendons Skeletal Muscles are usually attached to two bones on opposite sides of a jointCopyright © 2009 Pearson Education, Inc.Skeletal Muscles Work in Pairs The origin of the muscle is attached to the bone that remains stationary during movement The insertion is attached to the bone that moves  Bones act as levers in working with skeletal muscles to produce movementCopyright © 2009 Pearson Education, Inc.Skeletal Muscles Work in PairsFigure 6.1a(a) FlexionThe relaxed tricepsis stretched.The biceps contracts and pulls the forearm up, flexing the arm.Origin of muscle:attachment of muscle to less moveable boneInsertion of muscle:attachment of muscle to more moveable bone12/27/20093Copyright © 2009 Pearson Education, Inc.Functions of Skeletal Muscles1. Support the body – maintain our posture2. Movement of bones, and other tissues3. Help maintain a constant body temperature – generates heat4. Helps move blood through the veins and lymphatic fluid through the lymphatic vessels5. Help to protect vital organs and stabilize jointsCopyright © 2009 Pearson Education, Inc.Structure of Skeletal Muscles Muscles are covered by connective tissue called fascia. A muscle contains bundles of skeletal muscle fibers (muscle cells), the bundles are called fascicles. These bundles are covered by connective tissue. Blood vessels and nerves are between the fascicles.Copyright © 2009 Pearson Education, Inc.Structure of Skeletal MusclesFigure 6.3a–b(b) A light micrograph of a longitudinal view of skeletal muscle cellsSkeletal muscle consists of many bundles of muscle cells.A muscle cellconsists of manymyofibrils.A bundle of muscle cells is called a fascicle.(a) A section of askeletal muscleThe striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments.Copyright © 2009 Pearson Education, Inc.SarcomeresFigure 6.3b–c(b) A light micrograph of a longitudinal view of skeletal muscle cells(c) A diagram and electron micrograph of a myofibrilZ lineOne sarcomereThe striped (striated) appearance of a skeletal muscle cell is due to the regular arrangement of myofilaments.Copyright © 2009 Pearson Education, Inc.Muscle Cells Muscle cells are long cells called muscle fibers. The muscle fiber is composed of long thin myofibrils12/27/20094Copyright © 2009 Pearson Education, Inc.a. T tubule b. Sarcoplasmic reticulumc. myofibrild. Z linee. sarcomeref. sarcolemmaCopyright © 2009 Pearson Education, Inc.Muscle Cells cont Myofibrils are bundles of myofilaments that contracts.  Myofilaments are made of actin and myosin filaments. When muscle fibers are stimulated to contract, myofilaments slide past one another, causing sarcomeres to shorten.Copyright © 2009 Pearson Education, Inc.Muscle Cell Components Muscle cells (muscle fibers) have many of the same components as typical cells have but some of their components have different namesCopyright © 2009 Pearson Education, Inc.Muscle Cell Components Sarcolemma – plasma membrane (cell membrane) Sarcoplasm – similar to cytoplasm, contains large amount of stored glycogen and myoglobin. Myoglobin is an oxygen binding protein similar to hemoglobin, but found only in muscles Sarcoplasmic reticulum – similar to endoplasmic reticulum, one of its functions is to store Ca2+Copyright © 2009 Pearson Education, Inc.Muscle Cell Components Muscle cells (muscle fibers) also have unique features:  Multiple nuclei Transverse tubules (T tubules) – extensions of the sarcolemma that come into contact with the sarcoplasmic reticulum.12/27/20095Copyright © 2009 Pearson Education, Inc.Muscle Contraction The small myofibrils that make up the muscle fiber (muscle cell) contain two types of myofilaments: actin and myosin filaments Sarcomere is the name for the structural unit of these myofilaments The sarcomere goes between two dark lines = Z lines. The Z lines are protein sheets where the actin filaments attachCopyright © 2009 Pearson Education, Inc.SarcomeresFigure 6.3c–d(c) A diagram andelectron micrographof a myofibril(d) A sarcomere, the contractile unit of a skeletal muscle, contains actin and myosin myofilaments.Z lineZ lineZ lineActinMyosinOne sarcomereOne sarcomereCopyright © 2009 Pearson Education, Inc. The two myofilaments are: Actin filaments: thin filaments that formed by two intertwining strands of the protein actin. Myosin filaments: Thick filaments of the protein myosin shaped like a golf club, with a round “head”.Myofilaments – actin and myosinCopyright © 2009 Pearson Education, Inc. The myosin heads can bind and detach from the thin actin filament. When bound it creates cross-bridges.  When the muscle is stimulated, these filaments slide past each other, making the sarcomere to


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