If there are is low calcium in the blood, will the membrane potential?

I actually have no idea about this but I guess I could help,

Okay, firstly, lets see what we know...

1) We know that calcium ion is more outside the cells and inside the endoplasmic reticullum or sarcoplasmic reticulum in the case of muscle cells.

2) We know that this calcium ion gradient is very important for the proper functioning of the intracellular messaging and in the relaxation and contraction of muscle cells.


Okay, so we have a low calcium concentration in the blood, well I'm kinda confused, low as in lower than the concentration of calcium ion inside the cells? Then that would mean that the calcium ions inside the cells would move outside the cells.... Okay I give up

hmm let's see, I'll try hope this helps though  

the 2 main signs of large or abrupt changes in ionized calcium is to Increased neuromuscular excitability and cardiovascular effects.   

the function (general; non-patho) of ionized calcium:

    It stabilizes neuromuscular excitability, thereby making nerve cells LESS sensitive to stimuli. Therefore, nerves exposed to LOW ionized calcium levels show decreased thresholds for excitation, repetitive responses to a single stimulus, and, in extreme cases, continuous activity.   

some factors that affect the severity of manifestations of low ionized calcium levels:

   The underlying cause, rapidity of onset, accompanying electrolyte disorders, and extracellular pH.   

ways can increased neuromuscular excitability manifest:

   Paresthesias (tingling around the mouth and in the hands and feet), tetany (i.e., muscle spasms of the muscles of the face, hands, and feet), and, in severe hypocalcemia, laryngeal spasm and seizures.

I attach a site that hopefully will help to understand how muscles work..
http://health.howstuffworks.com/human-body/systems/musculoskeletal/muscle3.htm