1. End Show Slide 1 of 37 Copyright Pearson Prentice Hall 36–2 The Muscular System

2. End Show 36–2 The Muscular System Slide 2 of 37 Copyright Pearson Prentice Hall Muscles The function of the muscular system is movement. More than 40% of the mass of the average human body is muscle.

3. End Show 36–2 The Muscular System Slide 3 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue What are the three types of muscle tissue?

4. End Show 36–2 The Muscular System Slide 4 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue There are three different types of muscle tissue: Skeletal (is striated muscle) Cardiac (is striated muscle) Visceral (is smooth muscle)

5. End Show 36–2 The Muscular System Slide 5 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Skeletal Muscles Skeletal muscles: are usually attached to bones. are responsible for voluntary movements. have many nuclei. are made of striated muscles.

6. End Show 36–2 The Muscular System Slide 6 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Cardiac Muscle Cardiac muscle: is ONLY found in the heart. is striated muscle. may have one or two nuclei. They are connected by gap junctions that allow electrical impulses to travel among muscle cells.

7. End Show 36–2 The Muscular System Slide 7 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Visceral Muscles Smooth muscles: are usually involuntary control (most body organs). are spindle-shaped. have one nucleus. are made of smooth muscle. are found in many internal organs and blood vessels.

8. End Show 36–2 The Muscular System Slide 8 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Most smooth muscle cells can function without nervous stimulation. They are connected by gap junctions that allow electrical impulses to travel among muscle cells.

9. End Show 36–2 The Muscular System Slide 9 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Smooth muscle vs. Striated muscle

10. End Show 36–2 The Muscular System Slide 10 of 37 Copyright Pearson Prentice Hall Muscle Contraction The fibers in skeletal muscles are composed of smaller structures called myofibrils. Each myofibril has smaller structures called filaments. The thick filaments contain a protein called myosin. The thin filaments contain a protein called actin.

11. End Show 36–2 The Muscular System Slide 11 of 37 Copyright Pearson Prentice Hall Muscle Contraction Filaments are arranged along the muscle fiber in units called sarcomeres. Sarcomeres are separated by regions called Z lines. When a muscle is relaxed, there are no thin filaments in the center of a sarcomere.

12. End Show 36–2 The Muscular System Slide 12 of 37 Copyright Pearson Prentice Hall Muscle Contraction Skeletal muscle Bundle of muscle fibers Muscle fiber (cell) Myofibril Z line Sarcomere Myosin Actin

13. End Show 36–2 The Muscular System Slide 13 of 37 Copyright Pearson Prentice Hall Muscle Contraction How do muscles contract?

14. End Show 36–2 The Muscular System Slide 14 of 37 Copyright Pearson Prentice Hall Muscle Contraction A muscle contracts when the thin filaments in the muscle fiber slide over the thick filaments. This process is called the sliding filament model of muscle contraction.

15. End Show Slide 15 of 37 36–2 The Muscular System Copyright Pearson Prentice Hall Muscle Contraction During muscle contraction, the actin filaments slide over the myosin filaments, decreasing the distance between the Z lines. These lines are the same length. Notice that the contracted muscle is much shorter than the relaxed muscle.

16. End Show 36–2 The Muscular System Slide 16 of 37 Copyright Pearson Prentice Hall Muscle Contraction Binding sites Myosin Cross-bridge Actin Movement of Actin Filament

17. End Show 36–2 The Muscular System Slide 17 of 37 Copyright Pearson Prentice Hall Muscle Contraction During muscle contraction, the head of a myosin filament attaches to a binding site on actin, forming a cross-bridge.

18. End Show 36–2 The Muscular System Slide 18 of 37 Copyright Pearson Prentice Hall Muscle Contraction Powered by ATP, the myosin cross-bridge changes shape and pulls the actin filament toward the center of the sarcomere.

19. End Show 36–2 The Muscular System Slide 19 of 37 Copyright Pearson Prentice Hall Muscle Contraction The cross-bridge is broken, the myosin binds to another site on the actin filament, and the cycle begins again.

20. End Show 36–2 The Muscular System Slide 20 of 37 Copyright Pearson Prentice Hall Muscle Contraction When many myosin cross-bridges change shape in a fraction of a second, the muscle fiber shortens with considerable force. The energy for muscle contraction is supplied by ATP.

21. End Show 36–2 The Muscular System Slide 21 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact Skeletal muscles are joined to bones by tendons. Tendons pull on the bones so they work like levers. The joint functions as a fulcrum. The muscles provide the force to move the lever.

22. End Show 36–2 The Muscular System Slide 22 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact Opposing Muscles Contract and Relax

23. End Show 36–2 The Muscular System Slide 23 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact Opposing Muscles Contract and Relax

24. End Show 36–2 The Muscular System Slide 24 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact A controlled movement requires contraction by both muscles.

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26. End Show - or - Continue to: Click to Launch: Slide 26 of 37 Copyright Pearson Prentice Hall 36–2

27. End Show Slide 27 of 37 Copyright Pearson Prentice Hall 36–2 Skeletal muscles are joined to bones by tough connective tissue called a.ligaments. b.tendons. c.filaments. d.bursae.

28. End Show Slide 28 of 37 Copyright Pearson Prentice Hall 36–2 Muscle cells that are large, have many nuclei, and striations are a.skeletal muscle cells. b.smooth muscle cells. c.cardiac muscle cells. d.involuntary muscle cells.

29. End Show Slide 29 of 37 Copyright Pearson Prentice Hall 36–2 Muscle that is found in the walls of blood vessels and intestines is a.skeletal muscle. b.smooth muscle. c.cardiac muscle. d.striated muscle.

30. End Show Slide 30 of 37 Copyright Pearson Prentice Hall 36–2 The filaments found in skeletal muscle cells are a.actin and myosin b.myosin and myofibrils c.actin and Z lines d.actin and sarcomeres

31. End Show Slide 31 of 37 Copyright Pearson Prentice Hall 36–2 The type of muscle found only in the heart is a.skeletal muscle. b.striated muscle. c.cardiac muscle. d.smooth muscle.