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    Why does calcium channel blocker cause relaxation of muscles and dilation of vessels?

Posted on Mon, 19 May 2014 in Hypertension and Heart Disease
Question: Hi,
Can you tell me why a calcium channel blocker would cause relaxation of muscles and dilation of vessels, but hypocalcemia would cause hyperexcitability and possible tetany? This is very confusing to me.
Answered by Dr. Matija Romic 1 hour later
Brief Answer:
the answer is below

Detailed Answer:
Hello and thank you for asking HCM,

I will try to explain. Calcium blockers block the entry of calcium which prevents contractions, which means that without calcium your muscles (skeletal and smooth) cannot contract. During hypocalcemia, there is a change in membrane excitability, which leads to hyperexcitability.The main reason hypocalcemia causes neural excitability and tetany is due to its effect on the threshold potential of nerve axons. Low calcium reduces the amount that the threshold must change to initiate a full depolarization of the axon while leaving the resting potential unchanged. So depolarization which is needed for contraction and inervation is faster and shortened.
On the other hand, hypercalcemia leads to saturation channels and inability to release calcium from the cell leading to fatigue of cell.

I hope this answer was helpful to you.
Above answer was peer-reviewed by : Dr. Yogesh D
Follow up: Dr. Matija Romic 16 hours later
Dear Dr. Romic,
It really does help thank you so much! I find it difficult to memorize lists of reactions without knowing the mechanism of action. Thanks for taking the time to answer. The electrolytes are driving me crazy. XXXXXXX
Answered by Dr. Matija Romic 15 hours later
Brief Answer:

Detailed Answer:
I am glad it helped you.

Please close the discussion if you have no more questions..

Above answer was peer-reviewed by : Dr. Prasad
Answered by
Dr. Matija Romic

General & Family Physician

Practicing since :2012

Answered : 300 Questions


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