Filaments Resting state Electrical impulse (Action Potential) reaches axon terminal

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