Calcium Entry

Calcium levels must be maintained within certain limits in cells. Calcium is often considered a life or death signal in that, use of Calcium can be the difference between cell survival or cell death.Extracellular Calcium levels range between 2-5 mM.Intracellular Calcium levels range between 100-200 nM.The Endoplasmic Reticulum and Nucleus can act as Intracellular stores of Calcium.Homeostasis of Calcium is achieved by a delicate balance of multiple factors. Calcium entry is essential for Calcium Homeostasis.Voltage operated receptors:L type - HIGH voltage, long lasting effects. BAYK is an agonist, DHPs is an antagonist.N type - HIGH voltage, Fast inactivationT type - LOW voltage, fast inactivation.Receptor Operated Calcium Channels: NMDA Receptor - Glutamate activated Calcium channel. Depolarising of cell is neccessary to remove Magnesium block to get Calcium flowAMPA Receptor - Allows Calcium entry into cellM2 receptor decides Calcium permeability.Q - Glutamine form is permeable while theR - Arginine form is impermeable to CalciumCalcium can be used in a cell to effect Potassium hyperpolarisation of a cell, Chloride depolarisation of a cell.