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____ Chapter 49 ~ Sensory and Motor Mechanisms
(Just focusing on motor
mechanisms) Motor Mechanisms
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Vertebrate Skeletal Muscle Contract/relax: antagonistic
pairs w/skeleton Muscles: bundle of….
Muscle fibers: single cell w/ many nuclei consisting of…. Myofibrils: longitudinal bundles
composed of…. Myofilaments:
Thin~ 2 strands of actin protein and one strand of a regulatory protein
Thick~ staggerd arrays of myosin protein
http://entochem.tamu.edu/MuscleStrucContractswf/index.html
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Vertebrate Skeletal Muscle
Sarcomere: repeating unit of muscle tissue, composed of….
Z lines~sarcomere border I band~only actin protein A band~actin & myosin protein overlap H zone~central sarcomere; only myosin
http://www.sumanasinc.com/webcontent/animations/content/muscle.html
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Sliding-filament model Theory of muscle contraction Sarcomere length reduced Z line length becomes shorter Actin and myosin slide past each other (overlap increases)
http://www.blackwellpublishing.com/matthews/myosin.html
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Actin-myosin interaction 1- Myosin head hydrolyzes ATP to ADP and inorganic
phosphate (Pi); termed the “high energy configuration” 2- Myosin head binds to actin; termed a “cross bridge” 3- Releasing ADP and (Pi), myosin relaxes sliding actin;
“low energy configuration” 4- Binding of new ATP releases myosin head Creatine phosphate~ supplier of phosphate to ADP
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Muscle contraction regulation, I
Relaxation: tropomyosin blocks myosin binding sites on actin
Contraction: calcium binds to toponin complex; tropomyosin changes shape, exposing myosin binding sites
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html
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Muscle contraction regulation, II
Calcium (Ca+)~ concentration regulated by the….
Sarcoplasmic reticulum~ a specialized endoplasmic reticulum
Stimulated by action potential in a motor neuron
T (transverse) tubules~ travel channels in plasma membrane for action potential
Ca+ then binds to troponin
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Materials Muscle model/chicken wing The following is needed for each student: 4
red/black licorice strands (the thick twisted type)
10 red licorice strands (the thin type) a paper towel; toothpicks one raw chicken wing one dissection tray; dissection tools, gloves.
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Muscle cell simulation: contraction/relaxation
Procedure: Two thin pieces of licorice intertwined to
represent thin actin filaments Thick licorice to represent thick myosin
fibers Toothpicks represent the Z lines where thin
filaments attach