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CU-Boulder IPHY 3410 - Muscles: An Overview and Skeletal Muscle

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IPHY 3410 1st Edition Lecture 7Outline of Last Lecture 1) Distinguish between axial skeleton and appendicular skeleton2) Identify the specific locations of cartilages in the adult body3) Explain the functions of cartilage.4) Explain the functional properties of cartilage itself.5) Identify the unique characteristics and locations of hyaline, fibro-, and elastic cartilages.6) Compare the three kinds of cartilage in terms of structure, function, and location. 7) Explain why bones are considered organs. Discuss the tissues comprising a bone.8) List and explain the main functions of the bony skeleton.9) Classify bones according to shape; include several examples for each category.10) Describe the gross anatomy of a typical long bone.11) Describe where compact and spongy bones are located in a long bone. 12) Differentiate the histology of compact and spongy bone.13) Explain why Prof. Kram dislikes the term “spongy bone”14) Explain why spongy bone and compact bones are found where they are in a long bone.15) Describe the structure, function, and relationship among central canal, perforating canal, lamellae, lacuna, and canaliculi.Outline of Current Lecture Skeletal Muscle1) Describe the functions & characteristics of muscle tissue that distinguish it from other types of tissues.2) Name the layers of connective tissue that occur in and around a skeletal muscle.3) Describe and explain the structural and organizational levels of skeletal muscle. Begin with the muscle as an organ followed by the fascicle, muscle fiber, myofibril, and sarcomere, then end with the myofilament.4) List general characteristics of skeletal muscle fibers.5) Explain the sliding filament theory in the simplest form.6) Describe the role of titin in the sarcomere.Current LectureMuscleFunction of muscle tissue- Muscle tissues generate force in response to a stimulus from the nervous system in order to:o Move material through the bodyo Move, slow, or stabilize parts of the body and produce overall movement (ex: locomotion)o To generate heat (intentional or not)Properties of Muscle Tissue- Excitability – muscle cell responds to a neural/electrical stimulus- Contractility – in response to stimulus, muscle cells generate tension force and contracts or resists lengthening- Extensibility – when excitation ends, muscle cells can be easily stretched back to resting length- Elasticity – muscle cells can be stretched beyond its resting length and then it passively shortens back to resting length (like a spring)- Note: muscle cells only exert pulling forces; they cannot push. But pulling forces can resist lengthening 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.Types of Muscle Tissue- Skeletal muscleo Moves the skeletono Approximately 40% of body weighto Under voluntary controlo Striated - Cardiac muscleo Only found in heart wallo Under involuntary controlo Striated- Smooth muscleo In walls of most internal organs and bloods vessels o Under involuntary controlo Note: 1 muscle cell = 1 muscle fiberStructures found in all 3 muscle types- Muscle fiber – a muscle cell- Sarcolemma – plasma membrane- Sarcoplasm – cytoplasm of a muscle cell- Myofilaments – cytoskeletal unito Thin (actin) filamentso Thick (myosin) filaments- Myofibrils - rodlike bundles of actin & myosin that run parallel within a muscle cell (fiber)- T tubule - extension of sarcolemma into cell, wraps around myofibrils: carry electrical stimulus into cell- Sarcoplasmic Reticulum – modified endoplasmic reticulum that stores and pumps calcium ionso Calcium triggers force generationSkeletal Muscle: An Overview- Attach to bone directly or via tendon - Some attach to skin- 1 muscle fiber (cell) can be the length of entire muscle (not usually)- Can range in length from <1 cm to 30 cm- Long, cylindrical, multinucleated cells (fibers)Connective Tissue Found in Skeletal Muscle- Endomysium - loose CT surrounding a single muscle fiber- Perimysium – dense CT surrounding a muscle fascicleo Fasicle – collection of muscle fibers- Epimysium – dense irregular CT surrounding a muscleVeins, Arteries, and Nerves- Veins – remove cellular waste- Arteries – provide oxygen nutrients- Nerves – innervate muscle cellsMicroscopic Anatomy of a Skeletal Fiber- Structure of a myofibril:o Sarcomere: functional units within a myofibril, repeat the entire length of each myofibril; organization w/in each sarcomere gives muscle a striated appearanceo Myofilaments: actin & myosino Z disc: protein disc joining adjacent sarcomeres Each sarcomere shortens a little bit, the result adding to the total shortening of the myofibralo A band: primarily myosin (thick filaments) Always stays the same lengtho I band: primarily actin (thin filaments)- Titin – huge, spring like protein that attaches z disc to myosinContraction of a Skeletal Muscle- During a contraction, actin & myosin filaments slide (“row”) past one another o (Sliding Filament Theory)- myosin heads attach to actin in the thin filaments, then pivot to pull the thin filaments inwardHelpful VideosMUSCLE ORGANIZATION & SLIDING FILAMENT THEORYhttp://www.youtube.com/watch?v=EdHzKYDxrKcMUSCLE CONTRACTIONhttp://www.youtube.com/watch?v=XoP1diaXVCISARCOMERE


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