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29 Cards in this Set
- Front
- Back
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Why is Ca2+ needed?
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Calcium is needed to activate the thin filaments
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Ca2+ binds to what protein in the thin filament?
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Calcium binds to troponin
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When calcium binds to troponin, what occurs?
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Troponin then movese tropomyosin which allows cross bridges to attach
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Where does the calcium come from?
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It is released from the terminal cisternae of the SR
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What causes the terminal cisternae of the SR to release calcium?
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Muscle AP
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After muscle stimulation stops, what happens to the calcium?
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It is rapidly pumped back into the SR
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What are the 2 roles of ATP in muscle contraction?
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ATP binding and ATP hydrolysis
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What does ATP bind to in the thick filament?
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The myosin head
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What does ATP binding to the myosin head accomplish?
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Forces head to detach from actin (cross bridges detach)
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What does ATP hydrolysis do in the thick filament?
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The energy from ATP hydrolysis is used to cock myosin head to its high-energy configuration
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ATP hydrolysis cocks the myosin head from what to what energy state?
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Low-energy to high-energy
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When the myosin head is cocked in high-energy position, has calcium been released from SR? Explain
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Yes because troponin has moved the tropomyocin
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What is the power (working) stroke? What is occurring?
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It is when the myosin head tilts forward from high to low energy state and pulls on actin to make thin filaments slide
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When ATP binds to myosin head and it detaches, what energy state is it in?
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Low-energy state
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When ATP hydrolyzes, the energy cocks the myosin head back to what energy state?
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High-energy state
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How long will the cross bridge cycle last?
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Cycle continues as long as calcium and ATP are available
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What is rigor mortis?
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It is the stiffness that occurs in muscles when someone dies
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When does rigor mortis occur?
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Occurs 3-4 hours after death
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When does rigor mortis peak?
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Peaks after about 12 hours
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When does rigor mortis disappear?
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Gradually disappears after 48-60 hours
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What causes rigor mortis?
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Lack of ATP in the muscle
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As a cell dies, what is still being released and what is still occuring?
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Some calcium is released and thus some cross bridge cycling occurs
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When ATP runs out, what happens to the cross bridges?
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The cross bridges can't detach and the muscle stays contracted
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Why does the muscle finally relax after rigor mortis?
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The muscle finally relaxes when the proteins degrade
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What is excitation-contraction coupling?
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Sequence of events by which transmission of a muscle AP along the sarcolemma leads to sliding of the myofilaments
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Why do we need to remove ACh from the synaptic cleft when neuron stops firing?
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Lets the muscle cell relax when neuron stops firing
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What enzyme degrades ACh?
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Acetylcholinesterase
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What occurs when AChE degrades ACh?
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ACh can no longer bind to Na+ and K+ channels so they close and turn off EPPs
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When ACh breaks down, what are it's two components?
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Acetyl and Choline
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