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Unformatted text preview: the myosin head
• Power stroke occurs 18 4/21/13 Cross Bridge Cycle
• ADP unbinds
• ATP binds to myosin head on its
binding site, causing detachment to
• ATP is hydrolyzed to ADP & Pi which
brings the myosin head to the energized
state again What Stops the Cycle?
• Two major steps must happen to stop
the cross bridge cycle from occurring
– Removing acetylcholine
– Removing calcium 19 4/21/13 What Stops the Cycle?
to end contraction, pump calcium back to the SR (active transport), remove ACh • Acetylcholine esterase breaks down
• Ca2+ is pumped back to SR How Can ACh Be Removed?
Ca2+ Neurotransmitter (ACh)
N a+ Ach esterase Muscle cell ACh receptor 20 4/21/13 Where Does the Muscle Get
the Energy From?
• Muscle get glucose and oxygen to
• There are three sources of energy
– Creatine phosphate
– Cellular respiration
– Glycolysis followed by fermentation Phosphogens
Creatine phosphate Arginine phosphate 21 4/21/13 What Causes Muscle
• Local increase of inorganic phosphate
• Build up of acid
• Depletion of energy tetanus, muscles exposed to clostridium tetani (releases toxins) muscles work more, jaw locks, muscles keep ﬁring wrinkles (overexcitations of motor neurons on the facial muscles so wrinkles appear) botox shot of clos. bot. inhibits release of NT and messes with Ca channels nerve gas: block the ability to degrade the signal, lots of ACh, hyper excitation of muscle 22...
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- Summer '07