Download - Overview of Muscle Tissue & How it Contracts
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Overview of Muscle Tissue & How it ContractsAnatomy & Physiology
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Muscle Tissue: Comparisons•Skeletal
▫attached to bones or skin▫cells singular, very long, cylindrical,
multinucleated▫voluntary▫striated▫contractions slow to fast
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Muscle Tissue:Comparisons•Cardiac:
▫walls of the heart▫branching chains of cells connected by
intercalated discs, ▫uninucleated & striated▫involuntary: pacemaker & nervous system
control▫slow contraction, rhythmic
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Muscle Tissue: Comparisons•Smooth:
▫walls of hollow viscera (except heart)▫cells singular, fusiform▫uninucleated, no striations▫involuntary, controlled by nervous
system, hormones, some chemicals, & stretch
▫contractions slow
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Muscle Fibers•all skeletal muscle cells referred to as
fibers•all 3 muscle tissue type contract
because of same 2 microfilaments: actin & myosin
•all have subunits with prefixes: myo- or sarco-
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Connective Tissue Wrappings of Skeletal Muscle
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Smooth Muscle Layers in GI Tract: Circular Inner/ Longitudinal Outer
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Muscle Functions1. Movement 2. Posture /Balance3. Stabilizing Joints4. Generating Heat
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Skeletal Muscle Microanatomy•Sarcolemma: plasma membrane•Sarcoplasma: cytoplasm•Myofilaments: actin or myosin•Myosin: 1 of 2 principle contractile
proteins•Actin: 2nd principle contractile protein•Sarcoplasmic Reticulum: SER •T-Tubules: ordered invaginations of
sacroplasmic reticulum into sarcoplasma
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Skeletal Muscle Properties1. Irritability
▫ ability to receive & respond to stimuli2. Contractility
▫ ability to forcibly shorten when adequate stimulus received
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Nerve Stimulus•1 motor neuron (nerve cell that innervates
a muscle fiber) may stimulate a few fibers or hundreds of them
•motor unit: 1 motor neuron & all the muscle fibers it stimulates
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Nerve Stimulus•axon: extension from cell body that
carries the nerve impulse (action potential) to wherever neuron needs to send it
•axon terminal: end of axon
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Neuromuscular Junction• junction between axon terminals
surface of muscle fiber•Synapse: (synaptic cleft) gap filled
with interstitial fluid
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NMJ•neurotransmitter : chemical
(messenger molecule) released from axon terminal
•synaptic vesicles: vesicles that store neurotransmitter molecules in axon bulb until action potential hits which causes vesicle exocytose
•acetylcholine: neurotransmitter in all motor neurons
•motor end plate: portion of sarcolemma that has receptor proteins for acetylcholine
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•http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__function_of_the_neuromuscular_junction__quiz_3_.html
•http://www.wisc-online.com/objects/ViewObject.aspx?ID=AP2804
•http://faculty.massasoit.mass.edu/whanna/201/201_content/topicdir/muscle/muscle_media/muscle_VD/page142/page142.html
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Mechanisms of Muscle Contraction
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Sliding Filaments Animation•http://www.sci.sdsu.edu/movies/actin_myo
sin_gif.html
•http://www.3dotstudio.com/zz.html
•http://www.blackwellpublishing.com/matthews/myosin.html
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Muscle Movements•Origin: muscle attachment to the
immovable or less movable bone•Insertion: muscle attachment to the
movable bone
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Flexion •generally in sagittal plane•decreases the angle of the joint &
brings 2 bones closer together•Hinge Joints•Ball-and-Socket Joints
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Extension •movement that increases the distance
between 2 bones or parts of the body•If > 180◦ it is hyperextension
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Rotation •movement of a bone around its
longitudinal axis•Ball-and-Socket Joints•Atlas/Dens (shaking head “no”)
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Abduction•moving a limb away fro the midline,
or median plane• includes fanning fingers or toes
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Circumduction •proximal end stationary•distal end moves in a circle• limb as a whole outlines a cone
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Dorsiflexion • lifting foot so the dorsum of the foot
(top of foot) approaches the shin•corresponds to extension of the hand
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Plantar Flexion •depressing the foot ( pointing the
toes)•corresponds to flexion of the hand
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Supination •“turning backward”• forearm rotates laterally so palm
faces anteriorly•radius &ulna are parallel
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Pronation •“turning forward”• forearm rotates medially so palm
faces posteriorly•radius crosses ulna
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Opposition •thumb touches tips of other fingers on
same hand