synapse – the site of connection between a neuron and a cell. neurotransmitter – a chemical...
TRANSCRIPT
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Muscle Contraction
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• Synapse – The site of connection between a neuron and a cell.
• Neurotransmitter – A chemical released at the neuron’s synapse that communicates with the cell
• Motor Neuron – Neuron that controls effectors (such as skeletal muscle movement)
• Neuromuscular Junction – Synapse where a motor neuron and a muscle fiber meet
• Synaptic Cleft – Space that separates the neuron and the muscle fiber
Neuromuscular Junction
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• An action potential is conducted down a motor neuron
STEP 1
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• The motor neuron terminal releases the neurotransmitter acetylcholine (ACh) into synaptic cleft
STEP 2
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• ACh binds to ACh receptors on the sarcolemma.
STEP 3
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• The sarcolemma is stimulated which sends an action potential throughout the sarcolemma and deep into the muscle fiber through T-Tubules
Step 4
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• The action potential reaches the sarcoplasmic reticulum, which opens calcium channels
Step 5
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• Calcium ions diffuse from the sarcoplasmic reticulum into the sarcoplasm where they bind with troponin molecules
Step 6
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• Tropomyosin molecules move and expose specific binding sites for the myosin heads on actin
Step 7
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• Actin and Myosin link, forming cross-bridges
Step 8
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• POWER STROKE!!!• In other words the myosin heads use ATP to
pull the thin filaments towards the center of the sarcomere by cocking their heads
Step 9
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• When sarcomeres shorten, the thick and thin filaments do not change length, rather the thin filament slides past the thick filament.
Sliding Filament Model
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• If contraction is to continue, ADP and P are released from myosin heads
Step 10
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• New ATP binds to myosin head which releases the linkage between myosin and actin
Step 11
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• Actin and Myosin form cross bridge once again• Power Stroke• Thin filament slides past thick filament• ADP and P released
Step 12
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• To relax, the neuron releases acetylcholinesterase, an enzyme that breaks down ACh
Step 13
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• Action potential down the sarcolemma is eliminated
Step 14
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• Calcium molecules are released from troponin and are transported back into the sarcoplasmic reticulum
Step 15
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• Troponin and Tropomyosin molecules inhibit the myosin heads from attaching to actin
Step 16
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• Muscle is relaxed, yet ready to be stimulated again
Step 17