Steps of Muscle Contraction
Overview of Muscle Contraction
Steps of Muscle Contraction Example 1
True or False: if false, choose the answer that best corrects the statement.
The events of excitation-contraction coupling involve converting the electrochemical signal to the mechanical movement of contraction.
True.
False, excitation-contraction coupling involves the reception of the nerve signal at the neuromuscular junction.
False, excitation-contraction coupling involves the movement of actin by the myosin power stroke.
False, excitation-contraction coupling involves propagation of the signal through the sarcolemma and T tubules.
Neurotransmitters & Action Potentials
Steps of Muscle Contraction Example 2
During an action potential, the phase where ___________ moves into the cell results in depolarization while the phase where ______________ exits the cell results in repolarization.
Na: K
Ca: Na
Na: Ca
K: Ca
A. Events at the Neuromuscular Junction
Steps of Muscle Contraction Example 3
What is the role of the calcium ion in the signaling of an action potential at the neuromuscular junction?
Calcium moves across the synaptic cleft to relay the signal to the muscle tissue.
Calcium causes the muscle cell to depolarize propagating the action potential.
Calcium is important for contraction in the sarcomere; it does not play a role at the axon terminal.
Calcium entering the axon terminal triggers the release of Acetylcholine into the synaptic cleft.
True or false: if false, choose the answer that best corrects the statement:
The motor neuron is in contact with the sarcolemma in order to efficiently pass the electrical signal to the muscle fiber.
True.
False: the axon terminal touches the endomysium.
False: the motor neuron forms a synapse with the muscle fiber at the neuromuscular junction.
False: the axon terminal touches the sarcolemma passing on a chemical signal.
B. Excitation-Contraction Coupling
Steps of Muscle Contraction Example 4
Voltage gated channels respond to the depolarization of an action potential by releasing Ca. Where are these channels located?
Sarcolemma.
Sarcoplasmic Reticulum.
Sarcomere.
T-Tubule.
How does tropomyosin regulate muscle contraction?
Tropomyosin binds calcium, changing the confirmation of troponin.
Tropomyosin prevents myosin heads from binding to actin in the absence of calcium.
Tropomyosin wraps myosin preventing actin from binding in the absence of calcium.
Tropomyosin releases calcium during an action potential.
In a skeletal muscle fiber, which structure would you expect to have the greatest total surface area?
Sarcolemma.
Sarcoplasmic Reticulum.
Sarcomere.
T-Tubule.
C. Cross Bridge Cycle
Steps of Muscle Contraction Example 5
Which part of the cross-bridge cycle is called the power stroke?
Cocking of the myosin head.
ATP hydrolysis.
Myosin pulling the actin.
Binding of myosin heads to actin.
What would happen if a muscle completely ran out of ATP during a muscle contraction.
The myosin head would not move into the cocked position.
After the power stroke, the myosin would remain bound to the actin.
The myosin would bind to the actin, but the power stroke would not occur.
The sarcoplasmic reticulum would be unable to release calcium.
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- The ions that enter the skeletal muscle cell during the generation of an action potential are a. calcium ions...
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- What is the importance of acetylcholinesterase in muscle cell contraction?
- Explain what is meant by the term excitation-contraction coupling.
- Define and draw a motor unit.
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- Explain how a slight (but smooth) contraction differs from a vigorous contraction of the same muscle. Use the ...
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