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Motor mechanisms. Keywords (reading p. 1080-1086). Bundle, fiber, myofibril, sarcomere Z-line, thick filament, thin filament Actin, myosin, sliding filament model Molecular basis for filament movement Troponin, tropomyosin Sarcoplasmic reticulum Integration of synaptic signals

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keywords reading p 1080 1086
Keywords (reading p. 1080-1086)
  • Bundle, fiber, myofibril, sarcomere
  • Z-line, thick filament, thin filament
  • Actin, myosin, sliding filament model
  • Molecular basis for filament movement
  • Troponin, tropomyosin
  • Sarcoplasmic reticulum
  • Integration of synaptic signals
  • neurotransmitters
motor mechanisms3
Motor mechanisms
  • Create movement
  • Can be cilia, flagella, contractile proteins, muscles
  • Will focus on skeletal muscle
    • Muscle of vertebrates that is under voluntary control
structure of skeletal muscle
Structure of skeletal muscle
  • Bundle
  • Fiber
  • Myofibril
  • sarcomere

Part of Campbell 6th ed

p. 1081

features of muscle cells
Features of muscle cells
  • # of nuclei- multinucleate; formed by fusion of embryonic cells
  • length - this results in very long cells

Part of Campbell 6th ed

p. 1081

sarcomere
Sarcomere
  • Structure gives muscle a striated appearance
  • Z line, thick filaments (myosin), thin filaments (actin)

Part of Campbell 6th ed

p. 1081

at maximal contraction there is no space at end of thick filament thin filaments overlap
At maximal contraction, there is no space at end of thick filament,thin filaments overlap

Part of Campbell 6th ed

p. 1081

atp bound head retracted and unattached
ATP bound, head retracted and unattached

Part of Campbell 6th ed

p. 1082

hydrolysis of atp cocks head
Hydrolysis of ATP cocks head

Part of Campbell 6th ed

p. 1082

myosin head attaches to actin filament
Myosin head attaches to actin filament

Part of Campbell 6th ed

p. 1082

release of adp p i causes a further conformational change pushing against the actin filament
Release of ADP + Pi causes a further conformational change pushing against the actin filament

Part of Campbell 6th ed

p. 1082

cycle repeats and sarcomere shortens
Cycle repeats and sarcomere shortens

Part of Campbell 6th ed

p. 1082

control of muscle contraction by ca
Control of muscle contraction by Ca++
  • Tropomyosin- blocks the myosin binding sites on the actin filament when muscle is at rest
  • Troponin complex-binds calcium and controls the position of tropomyosin
at rest myosin cannot bind because sites are covered by tropomyosin
At rest, myosin cannot bind because sites are covered by tropomyosin

http://www.youtube.com/watch?v=WRxsOMenNQM

Part of Campbell 6th ed

p. 1083

slide20
During muscle contraction Ca++ levels rise. Ca++ binds to troponin which then pulls tropomyosin way from the binding sites

Part of Campbell 6th ed

p. 1083

structure of the sarcoplasmic reticulum
Structure of the sarcoplasmic reticulum
  • T tubules - are a network of the fiber plasma membrane that goes deep into the muscle fiber.
  • This allows transmission of the action potential into the fiber
sequence of events leading to muscle contraction
Sequence of events leading to muscle contraction
  • Motor neuron releases acetylcholine
  • Depolarization of the muscle fiber membrane results in action potentials
  • Action potentials trigger release of Ca++ from the sarcoplasmic reticulum
  • Increased Ca++ allows actin and myosin to slide against each other
characteristics of other muscle types
Characteristics of other muscle types:
  • Cardiac muscle - found only in the heart, striated, gap junctions allow direct electrical signaling between cells
  • Smooth muscle - involuntary muscle, meshwork of actin and myosin, can contract more (greater shortening), but with less tension.