Chapter 9 Notes.pdf - Chapter 9 Notes The Muscular System I...

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Chapter 9 Notes The Muscular System I. Introduction A. Muscles can only do one thing → contract B. Muscles contraction acts to 1. Move bones, circulates blood, and move food through the digestive system C. More than 600 individual skeletal muscles D. Each muscle is a distinct structure; however, muscles act in groups to perform particular movements II. Smooth Muscle A. Multiunit smooth muscle 1. When one fiber is stimulated, many adjacent fibers are also stimulated B. Visceral (single unit) smooth muscle 1. Sheets of cell in close contact with each other 2. Has autorhythmicity 3. Cells are tapered and have a single nucleus 4. No visible striations, even though they have actin and myosin filaments C. Visceral muscle produces an action called peristalsis 1. Rhythmic contraction that pushes substances through tubes of the body D. Respond to acetylcholine (ACh) and norepinephrine III. Skeletal muscle A. Striated or voluntary muscle 1. Actin and myosin responsible for the striations B. Body movement, maintaining of posture, and heat generation through shivering C. Respond ACh by contracting 1. Acetylcholinesterase breaks down ACh and cause muscle relaxation IV. Neuromuscular Junction A. Refer to image → V. Cardiac Muscle A. Found in the heart 1. Heart acts as a pump that moves blood B. Like smooth muscle 1. Involuntary muscle 2. Responds to ACh and norepinephrine C. Like skeletal muscle 1. Has striations created by the overlapping of thick (myosin) and thin (actin) contractile proteins known as filaments D. Cells are called cardiomyocytes 1. Have one nucleus and numerous mitochondria
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2. Cross bands called intercalated discs that permit the cells to work as a single unit E. In addition to having nerves innervate the heart, the heart is also autorhythmic VI. Applying Your Knowledge A. Skeletal muscle cells are autorhythmic 1. False B. Smooth and cardiac muscle cells have a single nucleus 1. True C. Skeletal muscle contraction is responsible for peristalsis 1. False VII. Structure of Skeletal Muscle A. Cells are called myocytes or muscle fibers because of their long lengths B. Cell membrane is called the sarcolemma C. Cytoplasm of this cell type is called sarcoplasm D. Endoplasmic reticulum is called sarcoplasmic reticulum E. Most of the sarcoplasm is filled with long structures called myofibrils 1. Arrangements of the action and myosin filaments in myofibrils that produces the striations F. Wrapped in connective tissue coverings 1. Endomysium is the connective tissue surrounding an individual muscle cell 2. Perimysium is a sheath of connective tissue surrounding a group of 10 to 100 muscle fibers a) Grouping of muscle fibers is called a fascicle 3. Epimysium is dense irregular connective tissue that surrounds an entire muscle G. Fascia 1. Connective tissue located just below the skin 2. Helps support muscles bones, nerves, and blood vessels H. Tendon 1. Tough, cord-like structure made of fibrous connective tissue 2. Connects a muscle to a bone I. Ligament 1. Tough fibrous connective tissue 2. Binds bone to bone J. Aponeurosis is a broad, sheet-like structure 1. Fibrous connective tissue 2.
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