filaments
Post on 23-Feb-2016
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Filaments
Resting state
Electrical impulse (Action Potential) reaches axon terminal
Impulse opens Calcium Channels, rapid influx of Calcium into terminal
Vesicles with acetylcholine (Ach) bind to cell membrane & releases Ach into synaptic cleft
Vesicles with acetylcholine (Ach) bind to cell membrane & releases Ach into synaptic cleft
Ach
Ach binds to receptors on motor end plate
Ach receptors opens Na+ channels, causes an influx of sodium into muscle
Sodium influx triggers a muscle impulse (electrical signal) in all directions of muscle fiber.
Electrical impulse travels across Sarcolemma, down t-tubules, and across cisternae
Sarcolemma
Electrical impulse travels across Sarcolemma, down t-tubules, and across cisternae
Sarcoplasmic Reticulum releases Calcium into Sarcoplasm
Sarcoplasmic Reticulum
Ca2+ (Calcium) Triggers muscle contraction by binding to troponin
Tropomyosin moves and exposes actin filaments to cross bridges
Cross bridges bind to actin & pulls actin forward (ADP is released from cross bridge)
Cross bridges bind to actin & pulls actin forward (ADP is released from cross bridge)
Videos
• Breakdown of ATP
• Synapse Transmission
• Action Potential Across Sarcolemma
• Shortening Sarcomere
Relaxation• Calcium pumps return Calcium to Sarcoplasmic reticulum• Acetylcholinesterase clears ACh from synaptic cleft• ATP binds to cross bridge & myosin is released from actin *• ATPase converts ATP to ADP using energy to cock cross
bridge*• Tropomyosin cover actin filaments
• * Note: ATP is required for both muscle contraction & relaxation
Myofibrils
• Actin Filaments “thin”– Anchored to z-lines (filament proteins)– I bands (light color) = actin + z-lines
• Myosin Filaments “thick”– A-band (dark color) = Myosin filaments + overlapping Actin filaments– H-zone (slightly lighter) = Myosin filaments between overlapping actin
• Sarcomere
– Area between 2 z-lines– Functional unit of skeletal muscle– During contraction adjacent z-lines approach each other
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