Anonymous asked in Science & MathematicsBiology · 8 years ago

Explain what happens after ACH attaches to receptors, sodium floods in and muscle becomes depolarized?

IB Biology

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  • 8 years ago
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    there is an end plate potential (local graded depolarisation) which spreads in both directions. It is above threshold so voltage-gated sodium channels in the muscle cells open and allow the influx of sodium, which then causes an action potential which spreads down the membrane of the muscle cell. The muscle cells have many T-tubules which the action potential runs down and back up. This causes voltage gated calcium channels in the membrane of the T-tubules to open but the driving force for calcium entry is small because the concentration of calcium in the extracellular fluid is low. When they open they undergo a conformational change. Nearby there are organelles called sarcoplasmic reticulum which store large amounts of calcium and in the membrane of these organelles are sarcoplasmic reticulum (SR) calcium release channels. The voltage gated calcium channels in the T-tubule membrane when they undergo the conformational change, have a section which acts as a ligand and binds to the ligand binding site of the SR calcium release channel which opens these channels and allows the influx of calcium from the lumen of the SR to the cytoplasm of the muscles which causes a contraction.

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