Manganese Ions Block the Calcium Channels in the Cardiac Muscle

question 71

Multiple Choice

Manganese ions block the calcium channels in the cardiac muscle membrane.How would the presence of manganese in the extracellular fluid affect the contraction of the heart muscle?

• A) The plateau phase of contraction would be longer.
• B) The refractory period would be shorter.
• C) The heart would beat less forcefully.
• D) The heart rate would increase.
• E) The contraction phase would be prolonged.

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