Research the causes of these diseases that are similar to, or related to, Autoimmune Urticaria: 1  Idiopathic urticaria without angioedema. 2  Chronic urticaria.  Occult infection (e.g., sinusitis, oral infection, cholecystitis, vaginitis, prostatitis, hepatitis, HIV, tinea manus or pedis)
In muscle cells, it's stored in the sarcoplasmic reticulum. In other tissue cells, it's stored in the smooth endoplasmic reticulum.
Best Answer: When sodium enters the muscle cell it creates an electrical impulse that travels down the cell membrane. This impulse travels to an indention of the membrane called a T-tubule. This allows the impulse to reach an intracellular structure called the SER(Smooth Endoplasmic Reticulum) which releases Calcium into the cell.