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ANATOMY AND PHYSIOLOGY Chapter 7 The Muscular System Myo means Sarco means muscle Flesh (muscle) Remember the 3 types of muscle tissue? Skeletal Smooth Cardiac All muscle cells are called muscle fibers Skeletal Muscle fibers They can range up to 1 foot in length Voluntary or Involuntary Striated or nonstriated Single nucleus or multinucleated Skeletal Muscle Fibers Found Where? Attached to The Skeleton (bones) Skeletal Muscle Fibers Contract rapidly with great force. Fatigues easily Skeletal Muscle Fibers Fascia Sheet or band under skin or around muscles Skeletal Muscle Fibers Each muscle fiber is enclosed in a protective sheath called an endomysium Skeletal Muscle Fibers Each endomysium is grouped and wrapped by the perimysium which forms a bundle called a fascicle Skeletal Muscle Fiber Fascicles are grouped by a epimysium which covers the entire muscle epimysium perimysium fascicle endomysium Skeletal Muscle Fibers So…… Each muscle cell Fiber Endomysium Perimysium Fascicle Epimysium Fascia Covers each fiber Wrapped around groups of fibers Muscle fiber bundle or group Warpped around groups of fascicles Wrapped around entire muscle Tendons Anchor muscles Provide durability Conserve space Small, can easily pass over a joint Smooth Muscle Voluntary or Involuntary Striated or nonstriated Single nucleus or multinucleated Smooth Muscle Found Where? Walls of hollow organs like stomach, bladder, uterus, intestines, around blood vessels Smooth Muscle Arranged in sheets or layers Contraction is slow and sustained Slow to fatigue Cardiac Muscle Found only in the _____________ Arranged in spiral or S shaped bundles Cardiac Muscle Voluntary or Involuntary Striated or nonstriated Single nucleus or multinucleated Cardiac Muscle Contraction is slow and steady Slow to fatigue (hopefully not for about 90 100 years Functions of the Muscles Produce movement Skeletal muscles move the body Smooth muscles force fluids and other substances through the body Cardiac muscles circulate blood Functions of the Muscles Maintain Posture Skeletal muscles constantly work against gravity Functions of the Muscles Stabilize joints Especially muscle tendons Functions of the Muscles Generate Heat ATP _________ is used to power muscle contraction ¾ of its energy escapes as heat Skeletal Muscle Microscopic Anatomy Muscle cells are called fibers instead of cells because of their threadlike shape. Skeletal Muscle Microscopic Anatomy Sarcolemma Same as cell membrane Sarcoplasm Same as cytoplasm Sarcoplasmic Reticulum (SR) Similar to endoplasmic reticulum (ER) Skeletal Muscle Microscopic Anatomy Many mitochondria and many nuclei Skeletal Muscle Microscopic Anatomy Myofibrils Bundles of fine fibers. Made of myofilaments Segment of myofibrils. Many in each myofibril Sarcomere T-tubules Triad Runs transverse. Allows electrical current to run deep into the cell SR Myofilaments t-tubule SR Thick and thin. Make up the myofibrils Skeletal Muscle Microscopic Anatomy Myofilament Made of 4 protein molecules: Myosin Attracted to each other Actin Tropomyosin Tropin Covers myosin when at rest Holds tropomyosin in place. Effected by Calcium One more time! •Myofilament •Myofibril •Fiber •Endomysium •Perimysium •Epimysium •Fascia Makes a fassicle Cross bridges Heads of myosin molecules lean toward actin and form a bridge for messages to cross over Acetylcholine A neurotransmitter secreted at the motor end plates of skeletal muscle. These cause an electrical current called an action potential Cross bridges Arrange from smallest to largest: fiber What is the energy source for muscle contraction? 3 ATP 1 myofilament myofibril 2
