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Chapter 11

Chapter 11. Muscular System. INTRODUCTION. Motion results from alternating contraction (shortening) and relaxation of muscles; the skeletal system provides leverage and a supportive framework for this movement. The scientific study of muscles is known as myology . Chapter 10 Muscle Tissue.

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Chapter 11

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  1. Chapter 11 Muscular System

  2. INTRODUCTION • Motion results from alternating contraction (shortening) and relaxation of muscles; the skeletal system provides leverage and a supportive framework for this movement. • The scientific study of muscles is known as myology.

  3. Chapter 10Muscle Tissue • Alternating contraction and relaxation of cells • Chemical energy changed into mechanical energy

  4. OVERVIEW OF MUSCLE TISSUE • Types of Muscle Tissue • Skeletal muscle tissue is primarily attached to bones. It is striated and voluntary. • Cardiac muscle tissue forms the wall of the heart. It is striated and involuntary. • Smooth (visceral) muscle tissue is located in viscera. It is nonstraited (smooth) and involuntary.

  5. MediaPhys2.0 • Let’s take a look at the muscle fibers contracting (5.9)

  6. The voluntarily controlled muscles of the body make up the muscular system. • The muscular system and muscle tissue contribute to homeostasis by producing movement, stabilizing body position, regulating organ volume, moving substances within the body, and producing heat. • This chapter discusses how skeletal muscles produce movement and describes the principal skeletal muscles.

  7. Muscle Attachment Sites:Origin and Insertion • Skeletal muscles shorten & pull on the bones they are attached to • Origin is the bone that does not move when muscle shortens (normally proximal) • Insertion is the movable bone (some 2 joint muscles) • Fleshy portion of the muscle in between attachment sites = belly

  8. Coordination Within Muscle Groups • Most movement is the result of several muscle working at the same time • Most muscles are arranged in opposing pairs at joints • prime mover or agonist contracts to cause the desired action • antagonist stretches and yields to prime mover • synergists contract to stabilize nearby joints • fixators stabilize the origin of the prime mover • scapula held steady so deltoid can raise arm

  9. Where is the…. • Prime mover (agonist) • Antagonist • Synergist

  10. Fascicle Arrangements • A contracting muscle shortens to about 70% of its length • Fascicular arrangement represents a compromise between force of contraction (power) and range of motion • muscles with longer fibers have a greater range of motion • a short fiber can contract as forcefully as a long one.

  11. HOW SKELETAL MUSCLES ARE NAMED • The names of most of the nearly 700 skeletal muscles are based on several types of characteristics. • These characteristics may be reflected in the name of the muscle. • The most important characteristics include the direction in which the muscle fibers run, the size, shape, action, numbers of origins, and location of the muscle, and the sites of origin and insertion of the muscle • Examples from Table 11.2 • triceps brachii -- 3 sites of origin • quadratus femoris -- square shape • serratus anterior -- saw-toothed edge

  12. Muscles of the Floor of the Oral Cavity • Suprahyoid muscles lie superior to hyoid bone. • Digastric m. extends from mandible to mastoid process • used to open the mouth • Mylohyoid m. extends from hyoid to mandible • supports floor of mouth & elevates hyoid bone during swallowing • Stylohyoid & Geniohyoid elevate the hyoid during swallowing

  13. Practice Question 1 • Which of the following is true? • Muscles pull on bones; they do not push bones. • The end of the muscle attached to the bone that moves least is the origin of that muscle. • The end of the muscle attached to the bone that moves most is the insertion of the muscle. • The main movement that occurs when the muscle contracts is the action of the muscle. • All of the above are correct.

  14. Practice Question 2 • Fascicle arrangements… • are named based on their orientation with the tendon of the muscle. • affect the power of muscles. • affect the range of motion of muscles. • A and B are correct. • A, B and C are correct.

  15. Practice Question 3 • A prime mover (agonist) • is the muscle most responsible for a particular action. • is opposed by contraction of a synergist. • is destabilized by contraction of a fixator. • is assisted by contraction of an antagonist. • All of the above are correct.

  16. Practice Question 4 • Which of the following may be the basis for the name of a muscle? • the direction of the muscle's fasicles • the size of the muscle • the action of the muscle • the location of the muscle • All of the above may be used to name a muscle.

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