Transcript Slide 1
Lesson Overview 32.2 The Muscular System Skeletal Muscle Cardiac Muscle Smooth Muscle - Striations -Controlled by nervous system. - Cells are large with many nuclei. - Similar to skeletal muscle in striated shape and similar to smooth muscle because is not under control of central nervous system. -Spindle-shaped cells with single nucleus. -Function without direct stimulation by nervous system Attached to the bones Found only in the heart Walls of stomach, blood vessels, and digestive system Lesson Overview The Muscular System Muscle Contraction During a muscle contraction, myosin filaments form cross-bridges with actin filaments. The cross-bridges then change shape, pulling the actin filaments toward the center of the sarcomere. Muscle fiber myofibrills Sarcomere Actin & miosin Lesson Overview Control of muscle) The Muscular System Muscle Motor neuron Acetylcholine (neurotransmitter) Activation of muscle fibers cell membranes Release of Ca+ ions Stimulation of myosin and actin interaction Contraction (skeletal Lesson Overview The Muscular System How Muscles and Bones Interact Skeletal muscles are joined to bones by the tendons. Tendons pull on the bones and make them work like levers. Lesson Overview The Muscular System • The joint (where two bones meet) functions as a fulcrum (the fixed point around which the lever moves) • The muscles provide the force to move the lever. Lesson Overview The Muscular System How Muscles and Bones Interact Most skeletal muscles work in opposing pairs—when one muscle contracts, the other relaxes. Lesson Overview The Muscular System Types of Skeletal Muscle Fibers. Present in all skeletal muscle and activated depending on need. Fibers type can be modified. RED FIBERS (40%) WHITE FIBERS (60%) slow contraction velocity fast contraction velocity Very resistant to fatigue. Work for long periods of time Fatigue easily. Generates more force Postural muscles of the neck. Activities that require great strength or quick bursts of speed, like sprinting, weight lifting Lesson Overview The Muscular System Exercise and Health RESTING MUSCLE TONE: state of partial contraction. Muscle tone keep the back and legs straight and the head upright, even when we are relaxed. Muscles that are exercised regularly stay firm and increase in size and strength.