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The Muscular System
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Structure and Function of Muscle Tissue
Muscle type Skeletal Cardiac Smooth Striated? Voluntary? Location? Regenerate Function?
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Structure and Function of Muscle Tissue
Muscle type Skeletal Cardiac Smooth Striated? Voluntary? Location? Throughout Body Heart Digestive tract, etc. Regenerate Limited No Yes Function? Movement
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Functions of muscle tissue important for Homeostasis
Movement Stabilizes body Regulates organ volume Produces heat Movement of food, urine, blood
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Layers of deep dense CT that surrounds muscle SG pg 108
Epimysium – entire muscle Perimysium – bundle of muscle fibers Endomysium – individual fibers
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Muscle Microanatomy A band – darkest color – most dense
thick and thin filaments overlap H band - medium color – medium density thick filaments only I band – lightest color – least dense thin filaments only
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Z disc – separate one sarcomere from another
M line – dark middle of sarcomere Myofibrils – 1 – 2 micrometers in diameter Sarcomere – contractile unit Sarcolemma – plasma membrane of muscle fiber Sarcoplasm – cytoplasm of muscle fiber
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Sarcoplasmic reticulum – fluid-filled sacs around each myofibril
During the contraction phase – thin filaments move towards M line Ach (acetylcholine) released at neuromuscular junction
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Muscle Ultrastructure
Muscle fiber Myofibrils Filaments
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Basics of Muscle Contraction SG pg 110
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Animation of Muscle Contraction
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Isometric exercises – exercise with an immovable resistant object
Contraction with NO movement Isotonic exercises (aerobic exercise) – exercise with movement Contraction with movement
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Skeletal muscles cooperate!
Muscles can only pull or contract – so most body movements are the result of muscles acting together or against each other. Prime movers Antagonists Synergists Fixators
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Origin – end of muscle attached to immovable bone
Insertion – end of muscle attached to movable bone
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Naming Muscles Action Direction of Fibers Location Number of Origins
Points of attachment of origin and insertion Size or Shape
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ANATOMY STUDY WEBSITE ANATOMY ARCADE GAMES
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Muscles that move the Head and Neck
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Muscles that move the Trunk
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Posterior
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Pelvis, Hip, and Thigh
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Lower Leg
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Atrophy – shrinking of muscle tissue from lack of use
Hypertrophy – enlargement of existing muscle cells Hyperplasia – increase in the number of muscle fibers
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Muscles and Aging Beginning at around 30 years, slow, progressive loss of skeletal muscle tissue Replaced by fibrous CT and adipose tissue Decrease in muscle strength Slower muscle reflexes Loss of flexibility
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Common Muscle disorders
Myasthenia gravis – Autoimmune disorder that causes chronic, progressive damage of the neuromuscular junction Muscles of face and neck 1 in 10,000 people Mostly women
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Muscular Dystrophy A group of inherited muscle- destroying disorders that target specific muscle groups Cause is the lack of a protein muscle fibers No cure Ex. Duchenne’s MD
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Fibromyalgia Painful, nonarticular rheumatic condition
more common in women Affects fibrous CT of muscles, tendons, and ligaments
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Abnormal contractions
Spasm Sudden involuntary contraction of a single muscle in a large group of muscles Cramp Painful spasmodic contraction Inadequate blood flow, overuse, dehydration, injury Holding a position for a long time Low potassium level Tremor Rhythmic, involuntary, purposeless contraction Quivering or shaking motion Fasciculation Twitching often seen in MS Fibrillation Spontaneous contraction only seen by electromyography Tic – spasmodic twitching of a muscle normally under voluntary control
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Muscle cramps Muscle strain Not enough Calcium Lack of oxygen
Tearing of a muscle Bleeding within muscle and severe pain Treat with RICE Rest Ice Compression Elevation
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Causes of muscle fatigue
Muscle fatigue – when a muscle is unable to contract even when it is still being stimulated Oxygen depletion/debt from prolonged muscle activity Lactic acid buildup ATP depletion
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Oxygen Debt O2 debt, which occurs after vigorous muscle activity, must always be “paid back” This “pay back” begins when a person breathes rapidly and deeply after activity – this continues until the muscles have enough O2 to get rid of the lactic acid buildup
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