edu2hbs human body systems 1 the muscular system 1
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EDU2HBS Human Body Systems
The Muscular System 1The Muscular System 1
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EDU2HBS Human Body Systems
Muscles are responsible for all types of body movement
Three basic muscle types are found in the body
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EDU2HBS Human Body Systems
Characteristics of MusclesCharacteristics of Muscles
Muscle cells are elongated (all muscle cells are called muscle fibers)
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh
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EDU2HBS Human Body Systems
Skeletal Muscle CharacteristicsSkeletal Muscle Characteristics
Cells are multinucleate
Striated – have visible banding
Cells are surrounded and bundled by connective tissue
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EDU2HBS Human Body Systems
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EDU2HBS Human Body Systems
Connective Tissue Wrappings ofConnective Tissue Wrappings ofSkeletal MuscleSkeletal Muscle
Endomysium – around single muscle fiber
Perimysium – around a fascicle (bundle) of fibers
Fascia – on the outside of the epimysium
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EDU2HBS Human Body Systems
Skeletal Muscle AttachmentsSkeletal Muscle Attachments Epimysium blends into a connective
tissue attachment Tendon – cord-like structure
Aponeuroses – sheet-like structure
Sites of muscle attachment
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EDU2HBS Human Body Systems
Smooth Muscle CharacteristicsSmooth Muscle Characteristics Has no striations
Spindle-shaped cells
Found mainly in the walls of hollow organs
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EDU2HBS Human Body Systems
Cardiac Muscle CharacteristicsCardiac Muscle Characteristics Has striations
Usually has a single nucleus
Joined to another muscle cell at an intercalated disc
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EDU2HBS Human Body Systems
Function of MusclesFunction of Muscles
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EDU2HBS Human Body Systems
Microscopic Anatomy of SkeletalMicroscopic Anatomy of SkeletalMuscleMuscle
Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum
Figure 6.3a
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distrinct bands
Figure 6.3b
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Sarcomere
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thick filaments = myosin filaments
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Myosin and actin overlap somewhat
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EDU2HBS Human Body Systems
Microscopic Anatomy of Skeletal MuscleMicroscopic Anatomy of Skeletal Muscle
Sarcoplasmic reticulum (SR) – for storage of calcium Figure 6.3d
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EDU2HBS Human Body Systems
Nerve Stimulus to MusclesNerve Stimulus to Muscles Skeletal
muscles must be stimulated by a nerve to contract
Motor unit
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EDU2HBS Human Body Systems
Motor unitsMotor unitsDefinition: A motor neuron and all the
muscle fibers it contacts
– Motor neuron activation causes contraction of all associated muscle fibers
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EDU2HBS Human Body Systems
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EDU2HBS Human Body Systems
Nerve Stimulus to MusclesNerve Stimulus to Muscles
Neuromuscular junctions
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EDU2HBS Human Body Systems
Nerve Stimulus to MusclesNerve Stimulus to MusclesSynaptic cleft –
Nerve and muscle do not make contact
Area between nerve and muscle is filled with interstitial fluid Figure 6.5b
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EDU2HBS Human Body Systems
Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle Neurotransmitter – chemical released
by nerve upon arrival of nerve impulse
The neurotransmitter for skeletal muscle is acetylcholine
Neurotransmitter attaches to receptors on the sarcolemma
Sarcolemma becomes permeable to sodium (Na+)
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EDU2HBS Human Body Systems
Transmission of Nerve Impulse to Transmission of Nerve Impulse to MuscleMuscle
Sodium rushing into the cell generates an action potential
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EDU2HBS Human Body Systems
The Sliding Filament Theory of Muscle The Sliding Filament Theory of Muscle ContractionContraction Activation by nerve
causes myosin heads (crossbridges) to attach to binding sites on the thin filament
Myosin heads then bind to the next site of the thin filament
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EDU2HBS Human Body Systems
The Sliding Filament Theory of Muscle The Sliding Filament Theory of Muscle ContractionContraction
Slide 6.17b
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
This continued action causes a sliding of the myosin along the actin
Figure 6.7
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EDU2HBS Human Body Systems
The Sliding Filament TheoryThe Sliding Filament Theory
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EDU2HBS Human Body Systems
Contraction of a Skeletal MuscleContraction of a Skeletal Muscle Muscle fiber contraction is “all or none”
Within a skeletal muscle, not all fibers may be stimulated during the same interval
Different combinations of muscle fiber contractions may give differing responses
Graded responses – different degrees of skeletal muscle shortening
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EDU2HBS Human Body Systems
Muscle Response to Strong StimuliMuscle Response to Strong Stimuli
More fibers contracting results in greater muscle tension
Muscles can continue to contract unless they run out of energy