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fatima2005

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12 years ago Edited: 12 years ago, fatima2005

Can someone please help me with these questions?

The neurotransmitter responsible for increasing potassium permeability at the sa node is

And, in order to increase heart rate at the SA node:
A. K+ permeability across the membrane must increase
B. Na+ permeability across the membrane must increase
C. K+ impermeability across the membrane must increase
D. Na+ impermeability across the membrane must increase

Thanks a lot

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how_mendel

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12 years ago

Quote from: fatima2005 (12 years ago)

The neurotransmitter responsible for increasing potassium permeability at the sa node is

Acetylcholine

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Biology!

fatima2005 Author

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12 years ago

Thanks, do you have any idea on the answer to the last question:

In order to increase heart rate at the SA node:
A. K+ permeability across the membrane must increase
B. Na+ permeability across the membrane must increase
C. K+ impermeability across the membrane must increase
D. Na+ impermeability across the membrane must increase

My guess is B, but I am not sure. I appreciate it.

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how_mendel

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12 years ago

The SA and AV node do not have fast sodium channels like neurons, and the depolarization is mainly caused by a slow influx of calcium ions.

The calcium is let into the cell by voltage-sensitive calcium channels that open when the threshold is reached. The calcium channels are rapidly inactivated, soon after they open. Sodium permeability is also decreased. Potassium permeability is increased, and the efflux of potassium (loss of positive ions) slowly repolarises the cell.

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fatima2005 Author

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12 years ago

So, according to your answer, A and D could both be the right answers? Thinking Face

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