Chapter 5 Textbook Notes

Chapter 5 Textbook Notes - Chapter 5 Textbook Notes...

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Chapter 5 Textbook Notes Muscular Fitness- the ability of your musculoskeletal system to perform daily and recreational activities without undue fatigue and injury Muscular Strength- the ability of a muscle or group of muscles to contract with maximal force Muscular endurance- the ability of a muscle to contract repeatedly over an extended period of time Resistance training- also referred to as weight training or strength training and can be done with measured weights, body weight, or other resistive equipment Resistance exercises stress the body’s musculoskeletal system, which enlarges muscle fibers and improves neural control of muscle function, resulting in greater muscular strength and endurance I. How do Muscles Work Voluntary skeletal muscle- allows movement of the skeleton and generates body heat Involuntary cardiac muscle- exists only in the heart and facilitates the pumping of the blood through the body Involuntary smooth muscle- lines some internal organs and moves food through the stomach and intestines A. Skeletal Muscle Each skeletal muscle is surrounded by a sheet of connective tissue that draws together at the ends of the muscle, forming tendons Tendon- connective tissue attaching muscle to bone Muscular contractions allow for skeletal movement because muscles are attached to bones via tendons The attached muscles pull the bones, which pivot at joints, creating a specific body movement Within each skeletal muscle are individual muscle cells called muscle fibers. Fascicles- bundles of muscle fibers Within each muscle fiber are myofibril strands, each containing contractile protein filaments
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These filaments are made up of 2 kinds of proteins—actin and myosin—which are arranged in altering bands that give the whole cell a striped appearance The microscopic structure and function of actin and myosin allow them to slide across each other and shorten the muscle Shortening of the many fibers within a whole muscle causes a pattern of muscular tension called contraction It is this whole muscle contraction that moves bones and surrounding body parts Every muscle fiber can be categorized as either slow or fast Slow-twitch muscle fiber (Type I)- oxygen dependent and contract relatively slow, but can contract over long periods of time without fatigue (marathoners) Fast-twitch muscle fiber (Type II)- not oxygen dependent and contract more rapidly, but tire quickly. They produce greater muscle power (weight lifters) B. Muscle Contraction requires stimulation For a voluntary muscle to contract, your nervous system must send a signal directly to the muscle Motor unit- a motor nerve and all the muscle fibers it controls Small motor units are comprised of slow-twitch muscle fiber Large motor units are comprised of fast-twitch muscle fibers The strength of the muscle contraction depends on the intensity of the nervous system stimulus, number and size of motor units activated, and types of muscle fibers stimulated
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Chapter 5 Textbook Notes - Chapter 5 Textbook Notes...

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