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Muscular SystemsOverview
April 22, 2015Sutherlin ASTW. Crawford
Adapted from “The Anatomy of Domesticated Animals” and the Colorado Agriscience Curriculum
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The Muscular System
Function:• locomotion or movement• life support– gathering food– reproduction– simple body functions
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The Muscular System
Structure of muscles:– consist of mostly protein– found in bundles or sheets– connected to bones by tendons
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The Muscular System
Classification of muscles:– Voluntary– Involuntary
The lean portion of animals carcass is what is used for food (muscles)
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The Muscular System
• Voluntary– Under control of the animals will– All are straited (striped)– Flexor- decreases the angle between two bones
(biceps)– Extensor- opposite side and increases the angle of
two bones (triceps)
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The Muscular System
• Involuntary– Not under the control of the animals free will– Heart– Secretory organs- force out secretions– Digestive system- movement of food– Respiratory system– Smoothed or straited
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Let’s go further…
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Muscular System Functions
• Body movement• Maintenance of posture• Respiration• Production of body heat• Communication• Constriction of organs and vessels• Heart beat
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Properties of Muscle
• Contractility– Ability of a muscle to shorten with force
• Excitability– Capacity of muscle to respond to a stimulus
• Extensibility– Muscle can be stretched to its normal resting length and
beyond to a limited degree
• Elasticity– Ability of muscle to recoil to original resting length after
stretched
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Muscle Tissue Types
• Skeletal– Attached to bones– Nuclei multiple and peripherally located– Striated, Voluntary and involuntary (reflexes)
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Muscle Tissue Types
• Smooth– Walls of hollow organs, blood vessels, eye, glands, skin– Single nucleus centrally located– Not striated, involuntary, gap junctions in visceral smooth
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Muscle Tissue Types
• Cardiac– Heart– Single nucleus centrally located– Striations, involuntary
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Skeletal Muscle Structure
• Muscle fibers or cells– Develop from myoblasts– Numbers remain constant
• Connective tissue• Nerve and blood vessels
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Embryologic origin
• Muscle cells are the result of the conjoining of embryo cells called myoblasts
• Explains multiple nuclei
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Muscle Fibers
• Muscles are attached to bones by tendons– Tendon is the connective tissue– This tissue also encapsules the muscle and forms
the epimysium
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Muscle Fibers
• Skeletal muscle is made up of bundles of subunits called fasicles (or fascicles)
• Fascicles are covered by connective tissue call perimysium
• Fascicles are made up of muscle cells– Muscle cells = muscle fibers
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Muscle Fibers
• Muscle cells– Ensheathed in endomysium– Made up of long protein molecules call myofibrils– Myofibrils have two types of myofilaments• Thick myofilament• Thin myofilament
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Muscle Fiber
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Sarcomeres
• The myofibril is divided into chains of sarcomeres
• Sarcomeres are the sections of myofilaments that slide over one another as muscles contract and relax
• This is where the work happens
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Organization of myofilaments I:
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Sliding Filament Model
• Actin myofilaments sliding over myosin to shorten sarcomeres– Actin and myosin do not change length– Shortening sarcomeres responsible for skeletal
muscle contraction
• During relaxation, sarcomeres lengthen
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Sliding filament model II:
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Sarcomere Shortening
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