introduction to the muscular system. muscle –fascicles fibers fibers of a single fascicle always...
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Introduction to the Muscular System
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• muscle– fascicles
• fibers
• fibers of a single fascicle always parallel
• fascicles of a muscle can be arranged in various ways
Organization of Skeletal Muscle Fibers
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Muscles are classified by how the fascicles are organized
1. Parallel (e.g., biceps brachii muscle)• most common arrangement
2. Convergent (e.g.,pectoralis muscle)• fascicles fan or triangle shaped, converge to attach
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Muscles are classified by how the fascicles are organized
3. Pennate (unipennate, bipennate and multipennate)• fasicles form angle toward tendon
4. Circular (e.g.,orbicularis oris)• sphincter, contracts to reduce diameter of opening
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Classification of MuscleSkeletal- found in limbs
Cardiac- found in heart
Smooth- Found in viscera
Striated, multi- nucleated
Striated, 1 nucleus
Not striated, 1 nucleus
voluntary involuntary involuntary
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Origins and Insertions
• The ends of skeletal muscles are always attached to other structures– fixed end is called ORIGIN
• usually attached to bone or cartilage
– movable end is called INSERTION• usually attached to the bone it moves
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How are muscles named?
1. location in the body • e.g., temporalis muscle
2. Origin and Insertion• first part = origin, 2nd part = insertion
3. Fascicle Organization• e.g., Rectus means “straight”• e.g., transverse means “across”• e.g., oblique means “oblique angle”
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How are muscles named?
4. Relative Position• e.g., superficialis, internus, lateralis, etc…
5. Structural Characteristics (shape and size)• e.g., deltoid, rhomboid, major, longus, etc…
6. Action• e.g., abductor, extensor, rotator, etc…
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Characteristics of Muscle
• Skeletal and smooth muscle are elongated• Muscle cell = muscle fiber• Contraction of a muscle is due to
movement of microfilaments (protein fibers)
• All muscles share some terminology– Prefixes myo and mys refer to muscle– Prefix sarco refers to flesh
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Muscular Actions
• Agonists (prime mover)– responsible for a particular movement
• Antagonist– against movement of agonist
• Synergists– aid agonists, stabilize an action
• Fixators– specialized synergists– immobilize the origin of agonist so all tension is
exerted at the insertion point