1Identify and explain the steps that generate the action potential and that lead to the steps of muscle contraction
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This stimulus can be mechanical, chemical, or electrical, depending on the type of sensory neuron. Show more…
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8. Here is a jumbled summary of steps involved in muscle contraction. Put them into correct order in the following chart, and then place the number for each step in the correct location on the preceding diagram. • Calcium ions bind to troponin molecules of thin filaments. • Acetylcholine is released from synaptic vesicles. Active Reading Chapter 50 Skeletal Muscle • Acetylcholine binds to receptors on the muscle fibers. This allows Na+ ions to rush, causing depolarization. • The troponin/tropomyosin complex is moved so the myosin-binding site of actin is exposed. • Depolarization continues across the sarcolemma and down the transverse tubule system. • Ca++ is released from cisterns of the SR (sarcoplasmic reticulum). • Nerve impulse arrives at the neuromuscular junction. • Myosin heads rotate, bind the actin, and pull the actin fibers toward the center of the sarcomere. • In the presence of Ca++, myosin acts as an enzyme. It catalyzes breakdown of ATP. Energy is transferred from ATP to the myosin head; myosin is activated. Steps of Muscle Contraction 1. 2. 3. 4. 5. 6. 7. 8. 9.
Madhur L.
Describe the events that lead to muscle contraction beginning with a nerve impulse arriving at a neuromuscular junction. What molecules and ions are involved in each step and how are electrical and chemical signals passed from one structure to another (both from the neuron and within the muscle fiber). What is the ultimate trigger for contraction and how does it interact with regulatory proteins? How do the myofilaments interact during contraction?
Supreeta N.
Place the steps of Excitation contraction in order of occurrence. I have given you the first step below: 1. The brain sends an action potential (nerve impulse) down a motor neuron to a muscle. [ Choose ] Calcium influxes into the axon terminus causing a release of the neurotransmitter acetylcholine (ACh) into the synaptic cleft Tropomyosin moves away from the active sites on the actin filaments. Myosin heads bind to actin forming cross-bridges. ATP is hydrolyzed to ADP and inorganic phosphate, which reenergizes the myosin head, preparing it for another cycle of cross- Depolarization triggers an action potential that quickly spreads along the sarcolemma and down into the muscle fiber through Myosin heads pivot toward the center of the sarcomere pulling the actin filaments toward the middle Receptors on the motor end plate of the muscle fiber's sarcolemma open causing an influx of sodium The sarcoplasmic reticulum releases stored calcium ions into the cytosol of the muscle cell. ATP molecule binds to the myosin head causing it to detach from the actin. Ca2+ binds to the troponin complex on the thin filaments of the muscle fiber.
Kaela P.
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