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Membrane Potentials, Calcium and Muscle Contraction

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1. Explain, briefly, why the 10-fold difference in concentration of Na+ across the membrane is important to excitable membranes.
2. How do voltage-gated calcium channels relate to electrical activity of the neuronal vs. sarcolemmal membrane? Concentrate on the differences. Keep your answer brief (3-4 sentences).
3. Why are muscle action potentials only the result of excitation? Think about what hyperpolarization would do for contraction.

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380+ words explains the concentration differences in Na across excitable membranes and other related questions.

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Cells often actively pump out certain ions to polarize themselves - that is, to separate ions of different charges on opposite sides of a membrane - in order to use this gradient as a means to regulate their function. For example, neurons will do this and make use of the electrochemical gradient that builds up as a means of sending signals from one end of the neuron to the other, where more chemical signals are then stimulated by movements of this gradient to send a signal to another cell.

Excitable membranes are membranes which can depolarize, or alleviate the polarized build-up of ions on different sides of the ...

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