End Show Slide 1 of 37 Copyright Pearson Prentice Hall Biology

End Show Slide 2 of 37 Objectives Describe the three types of muscle tissue. Explain how muscles contract. Explain why exercise is important. Copyright Pearson Prentice Hall

End Show Slide 3 of 37 Copyright Pearson Prentice Hall 36–2 The Muscular System

End Show 36–2 The Muscular System Slide 4 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.

End Show 36–2 The Muscular System Slide 5 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue What are the three types of muscle tissue?

End Show 36–2 The Muscular System Slide 6 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue There are three different types of muscle tissue: skeletal smooth cardiac

End Show 36–2 The Muscular System Slide 7 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 sometimes called striated muscles.

End Show 36–2 The Muscular System Slide 8 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Smooth Muscles Smooth muscles: are usually not under voluntary control. are spindle-shaped. have one nucleus. are not striated. are found in many internal organs and blood vessels.

End Show 36–2 The Muscular System Slide 9 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.

End Show 36–2 The Muscular System Slide 10 of 37 Copyright Pearson Prentice Hall Types of Muscle Tissue Cardiac Muscle Cardiac muscle: is only found in the heart. is striated. may have one or two nuclei. Cardiac muscle cells are connected to each other by gap junctions.

End Show 36–2 The Muscular System Slide 11 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.

End Show 36–2 The Muscular System Slide 12 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.

End Show 36–2 The Muscular System Slide 13 of 37 Copyright Pearson Prentice Hall Muscle Contraction Skeletal muscle Bundle of muscle fibers Muscle fiber (cell) Myofibril Z line Sarcomere Myosin Actin

End Show 36–2 The Muscular System Slide 14 of 37 Copyright Pearson Prentice Hall Muscle Contraction How do muscles contract?

End Show 36–2 The Muscular System Slide 15 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.

End Show Slide 16 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.

End Show 36–2 The Muscular System Slide 17 of 37 Copyright Pearson Prentice Hall Muscle Contraction Binding sites Myosin Cross-bridge Actin Movement of Actin Filament

End Show 36–2 The Muscular System Slide 18 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.

End Show 36–2 The Muscular System Slide 19 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.

End Show 36–2 The Muscular System Slide 20 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.

End Show 36–2 The Muscular System Slide 21 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.

End Show 36–2 The Muscular System Slide 22 of 37 Copyright Pearson Prentice Hall Control of Muscle Contraction Impulses from motor neurons control the contraction of skeletal muscle fibers. A neuromuscular junction is the point of contact between a motor neuron and a skeletal muscle cell.

End Show 36–2 The Muscular System Slide 23 of 37 Copyright Pearson Prentice Hall Control of Muscle Contraction Vesicles in the axon terminals of the motor neuron release a neurotransmitter called acetylcholine. Acetylcholine produce an impulse in the cell membrane of the muscle fiber.

End Show 36–2 The Muscular System Slide 24 of 37 Copyright Pearson Prentice Hall Control of Muscle Contraction The impulse causes the release of calcium ions within the fiber. The calcium ions affect regulatory proteins that allow actin and myosin filaments to interact.

End Show 36–2 The Muscular System Slide 25 of 37 Copyright Pearson Prentice Hall Control of Muscle Contraction A muscle cell remains contracted until the release of acetylcholine stops and an enzyme produced at the axon terminal destroys any remaining acetylcholine. Then, the cell pumps calcium ions back into storage, the cross-bridges stop forming, and contraction ends.

End Show 36–2 The Muscular System Slide 26 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.

End Show 36–2 The Muscular System Slide 27 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact Opposing Muscles Contract and Relax

End Show 36–2 The Muscular System Slide 28 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact Opposing Muscles Contract and Relax

End Show 36–2 The Muscular System Slide 29 of 37 Copyright Pearson Prentice Hall How Muscles and Bones Interact A controlled movement requires contraction by both muscles.

End Show 36–2 The Muscular System Slide 30 of 37 Copyright Pearson Prentice Hall Exercise and Health Why is exercise important?

End Show 36–2 The Muscular System Slide 31 of 37 Copyright Pearson Prentice Hall Exercise and Health Regular exercise is important in maintaining muscular strength and flexibility.

End Show 36–2 The Muscular System Slide 32 of 37 Copyright Pearson Prentice Hall Exercise and Health Aerobic exercises help the body’s systems to become more efficient. Resistance exercises increase muscle size and strength.

End Show - or - Continue to: Click to Launch: Slide 33 of 37 Copyright Pearson Prentice Hall 36–2

End Show Slide 34 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.

End Show Slide 35 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.

End Show Slide 36 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.

End Show Slide 37 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

End Show Slide 38 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.

END OF SECTION