1)Compare and contrast the mechanisms of excitation-contraction in skeletal musc
ID: 3479103 • Letter: 1
Question
1)Compare and contrast the mechanisms of excitation-contraction in skeletal muscle and in smooth muscle. (PROVIDE AS MUCH DETAIL AS YOU CAN, also if you can do step by step so I can clearly distinguish what happens and in what order)2) Compare and contrast the mechanisms responsible for terminating muscle contractions, and allowing relaxation in skeletal muscle versus smooth muscle. (Assume that the stimulus to the muscle cell has already stopped, and focus your answer instead on what happens in the muscle cell.) 1)Compare and contrast the mechanisms of excitation-contraction in skeletal muscle and in smooth muscle. (PROVIDE AS MUCH DETAIL AS YOU CAN, also if you can do step by step so I can clearly distinguish what happens and in what order)
2) Compare and contrast the mechanisms responsible for terminating muscle contractions, and allowing relaxation in skeletal muscle versus smooth muscle. (Assume that the stimulus to the muscle cell has already stopped, and focus your answer instead on what happens in the muscle cell.)
2) Compare and contrast the mechanisms responsible for terminating muscle contractions, and allowing relaxation in skeletal muscle versus smooth muscle. (Assume that the stimulus to the muscle cell has already stopped, and focus your answer instead on what happens in the muscle cell.)
Explanation / Answer
Please post the second question as a separate entry. 2 different questions cannot be clubbed together as single entry.
1. Skeletal muscle:
In the muscle cells membrane depolarisation normally starts at the motor end plate. This depolarisation if large enough causes action potential in adjacent parts of the muscle cell membrane. This action potential is able to reach all the muscle fibrils in the cell interior via the T tubules.
The dihydropyridine (DHPR) receptor on the t tubule membrane acts as voltage sensor and triggers release of calcium ions from the terminal cisterns of the l tubule via a physical interaction with the ryanodine receptor in the sacrcoplasmic reticulum.
The released calcium binds to troponin c which allows it to get detached from the tropomyosin. The latter moves away uncovering active sites where myosin heads bind to actin.
This leads to the power stroke of muscle contraction.
Relaxation is brought about by active pumping of calcium back into sacrcoplasmic reticulum.
Smooth muscle:
There is initial binding of acetylcholine to muscarinic receptors. This leading to increased calcium influx into the cell and it's binding to calmodulin. This calcium calmodulin complex activates myosin light chain kinase (MLCK)
MLCK causes phosphorylation of myosin, increases myosin ATPase activity and it's binding to actin. This initiates cross bridge cycling and contraction.
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