RHS Anatomy & Physiology: Muscle Contraction Steps – Flashcards
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Step 1
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Action potential (AP) propagates along neurolemma to the synaptic end bulb.
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Step 2
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The AP causes a triggering of vesicle movement toward the synapse.
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Step 3
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Acetylcholine (ACh) filled vesicles fuse with membrane and undergo exocytosis.
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Step 3
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Acetylcholine (ACh) filled vesicles fuse with membrane and undergo exocytosis.
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Step 4
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ACh is released into synaptic cleft in search of ACh receptors.
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Step 5
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ACh binds causing ligand-gated ion channels to open allowing an influx of sodium ions.
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Step 6
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This triggers the muscle impulse along the sarcolemma and into the T-tubules.
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Step 7
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The muscle impulse propagates along the T-tubules triggering the sarcoplasmic reticulum (SR) to release calcium ions into the sarcoplasm.
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Step 8
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Calcium binds to troponin causing the troponin-tropomyosin complex to move.
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Step 9
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This movement causes the myosin-binding sites to become uncovered on the actin triggering the contraction cycle.
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Step 10
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The myosin attaches to the actin forming a cross-bridge.
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Step 11
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The pocket on the myosin head then opens, rotates, and releases the ADP.
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Step 12
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This action creates force pulling the actin toward the M-line.
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Step 13
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At this point, the ADP is released from the myosin head, triggering the power stroke.
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Step 14
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ATP then binds to the myosin head causing it to release the thin filament.
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Step 15
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ATP is hydrolyzed by the enzyme acetylcholinesterase (AChE) on the myosin head.
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Step 16
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The myosin continues to hold onto the ADP and phosphate while being energized.
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Step 17
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This cycle continues as long as ATP and calcium are available.
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Step 18
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Once the AP ceases, the SR calcium release channels close.
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Step 19
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Active transport pumps bring calcium into the sarcoplasmic reticulum.
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Step 19
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Active transport pumps bring calcium into the sarcoplasmic reticulum.
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Step 19
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Active transport pumps bring calcium into the sarcoplasmic reticulum.
